Gender Differences in Fat Metabolism

Chantal Vella, M.S. and Len Kravitz, Ph.D.
IntroductionThereThe incidence of obesity in America is currently on the rise. Approximately 25 percent of U.S. adult females and 20 percent of U.S. adult males are obese (National Heart, Lung, and Blood Institute, 2002). Over the last two decades, the number of cases of obesity in the U.S. has increased more than 50 percent (from 14.5 percent of the adult population to 22.5 percent). The primary cause of weight gain is an energy intake that constantly exceeds the amount of physical activity or energy expenditure of an individual. According to Blair and Nichaman (2002), a decrease in regular physical activity, and not an increase in energy intake, is responsible for the recent increase in obesity prevalence.

With the rising incidence of obesity there has been an increasing interest in investigating the determinants of fat metabolism (the complete breakdown of fat into usable energy) at rest and during exercise. Enhancing fat metabolism has become a key component in the battle of the bulge for many of our clients. Current research shows that, although exercise and training increase the amount of fat metabolized, there may be gender differences in the way we store and metabolize fat during rest and exercise. This article will provide an in-depth review on fat metabolism and explore the possible mechanisms involved in the differences in fat metabolism between men and women. Practical applications for prescribing exercise to maximize caloric expenditure and fat metabolism will also be presented.
How is Body Fat Stored?Fat is stored in the body in the form of triglycerides. Triglycerides (TG) are made up of three free fatty acid (FFA) molecules held together by a molecule of glycerol (not a fat but a type of alcohol) (Robergs & Roberts, 1997). Most of our body fat is stored in fat cells which are called adipocytes. Typically, about 50,000 to 60,000 kilocalories (kcals) of energy are stored as TG in fat cells throughout the body (Coyle, 1995). Fat can also be stored as “droplets” within skeletal muscle cells. These fat droplets are called intramuscular triglycerides (IMTG) and they may hold 2000-3000 kcals of stored energy. In addition to the stores of fat, some TG travel freely in the blood. During exercise, TG in fat cells, muscle cells, and in the blood can be broken down (a process called lipolysis) and used as fuel by the exercising muscles.
Gender Differences in Fat Storage It is well established that women generally have a higher percentage of body fat than men. A healthy range of body fat for women is 20-25%, and a healthy range of body fat for men is 10-15% (Robergs and Roberts, 1997). A body fat percentage over 20% for men or 30% for women is considered an indication of obesity. Body fat distribution varies among individuals and is a determinant of cardiovascular risk. Some people carry more of their body fat in and around the abdominal area. This type of fat deposition is called android, or apple body type and is most characteristic among males. The android body type is associated with a higher risk for cardiovascular disease. The body type most common among females is the gynoid, or pear body type. This body type is characterized by fat stores in the hip and thigh region (Robergs & Roberts, 1997). The scientific explanations for the dramatic difference in body fat distribution between men and women are largely unknown, although differences in hormones, hormone receptors, and enzyme concentrations play a contributing role. These possible mechanisms are discussed later in the section on epinephrine and lipolysis. See Sidebar 1 for two ways to determine your client’s body type and risk of cardiovascular disease.
Determining Body Type & Cardiovascular Risk Please place close to this content in the article)
A person’s body type is recognized as an important predictor of risk for hypertension (high blood pressure), hyperlipidemia (high cholesterol), coronary heart disease, type II diabetes, and premature death (ACSM, 2000). Individuals with more body fat in the abdominal area (android body type) are at increased risk of developing the above conditions compared with individuals who are equally fat, but have most of their fat in the hip and thigh regions (gynoid body type).

There are two ways to determine body type and health risk: waist-to-hip ratio and waist circumference. The waist-to-hip ratio is the circumference of the waist divided by the circumference of the hips. This measurement can be taken in inches or centimeters. To determine if your client has a healthy waist-to-hip ratio, use a measuring tape to measure the smallest part of the waist (usually above the belly button and below the chest) and the largest part of the hips. Make sure the measuring tape is horizontal all the way around the body when taking a measurement. When measuring the hip circumference have your client stand with their feet together. Take the measurement while standing next to your client. This will allow you to easily determine the largest and widest part of the hips. The standards for risk vary with age and sex. Ratios above .94 for young men and .82 for young women place the individual at very high risk of disease. For ages 60-69 years, ratios indicating very high risk are above 1.03 for men and .90 for women. Recently the expert panel on obesity and health risk developed the waist circumference measurement as an indicator of health risk. The waist circumference measurement is taken the same way as in the waist-to-hip ratio. A healthy waist circumference is below 102 cm (40 inches) for men and 88 cm (34 inches) for women (ACSM, 2000).
Mobilization and Metabolism of Fat The mobilization of fat refers to the process of releasing fat from storage sites in the body, whereas, metabolism of fat is the complete biological breakdown or oxidation (which means loss of electrons) of fat into energy that can be used by the body. There are two main enzymes that regulate the mobilization of FFA: hormone sensitive lipase (HSL) and lipoprotein lipase (LPL). HSL is located directly in the fat cell and is stimulated by the hormone epinephrine. When HSL is stimulated, it acts to break apart TG in the adipose tissue and release three FFA and glycerol into the blood stream. This process is called lipolysis. Epinephrine, which is released by the sympathetic nervous system during exercise, is the primary stimulator of lipolysis (Rasmussen & Wolfe, 1999). Epinephrine binds to specific receptors on the fat cell, which in turn, activate HSL. An individual’s physiological state can affect the body’s sensitivity to epinephrine. For example, during aerobic exercise, HSL responsiveness to epinephrine is enhanced due to an increase in body temperature and a greater concentration of epinephrine in the blood stream when compared to rest. In an endurance-trained individual the HSL responsiveness to epinephrine is further enhanced, such that HSL can be activated by a lower concentration of epinephrine when compared to a non-endurance trained individual. Therefore a metabolic training effect of aerobic exercise is an enhanced receptiveness to mobilize and break apart TG for energy use. In contrast, obesity blunts the HSL responsiveness to epinephrine, meaning a higher concentration of epinephrine is needed to activate HSL in obese individuals (Rasmussen & Wolfe, 1999).

Once in the blood stream, the FFA molecules bind to albumin, a blood protein and the main transporter of FFA molecules. FFA molecules are not water soluble and thus require a protein carrier to allow them to be transported to cells and within the blood stream. Once the FFA molecules are transported to the muscle cell, they are released from albumin and carried across the muscle cell membrane by specific transporters. There are three main FFA transporters located on the muscle cell membrane: fatty acid binding protein (FABP), fatty acid translocase (FAT), and fatty acid transport protein (FATP) (Turcotte, 2000). These proteins bind the FFA molecules and transport them across the cell membrane and to the mitochondria for complete oxidation. The number of FFA transporters on the muscle cell membrane can increase with aerobic training, thus enhancing the ability to metabolize fat. The glycerol molecule released from lipolysis is circulated to the liver for oxidation and is either used as an intermediate in the breakdown of glucose or used to make more TG (Robergs and Roberts, 1997).

LPL, the second enzyme of lipolysis, is located on blood vessel walls throughout the body. Both adipose tissue and the liver have large quantities of this enzyme. LPL acts on TG within lipoproteins in the blood stream. Lipoproteins are special transporters that carry cholesterol and TG through the blood stream to fat storage depots and body cells for fuel and cellular life-support needs. The TG are broken down to FFA molecules and used as fuel by active tissues or diffuse into fat and liver cells where they are re-synthesized into TG and stored. LPL is often referred to as the “gatekeeper” that controls the distribution of fat in the various storage depots of the body (Pollock & Wilmore, 1990)
Epinephrine & LipolysisEpinephrine is the primary hormone that stimulates lipolysis (Rasmussen & Wolfe, 1999). Epinephrine binds to receptors on various cells throughout the body, such as adipocytes and muscle cells, and can either activate or inhibit HSL (Blaak, 2001). The two main types of epinephrine receptors are alpha and beta receptors. Epinephrine can stimulate lipolysis through the beta receptors and can inhibit lipolysis through the alpha receptors (Blaak, 2001). The type of receptor available and its sensitivity to epinephrine will determine the response of HSL in any given tissue. It is interesting to note that alpha and beta receptors can be located on the same cells, however, depending on which receptor is more abundant and available for epinephrine binding determines the response of HSL. For example, research has shown that abdominal adipocytes are more sensitive to beta receptor stimulation by epinephrine than hip and thigh adipocytes in both men and women (Braun & Horton, 2001). This finding suggests that fat around the abdominal area is easier to mobilize than fat located in the hip and thigh areas. In addition, women tend to have a greater number of alpha receptors in the hip and thigh regions (Blaak, 2001). This would tend to favor the storage of fat, as opposed to the mobilization of fat, in the hip and thigh region. The differences in the type and number of cell receptors may be one of the mechanisms contributing to the differences in fat distribution between men and women (Blaak, 2001). Another mechanism contributing to the differences in fat distribution between men and women is the concentration of LPL in various tissues. Women have a higher LPL concentration and activity in the hip and thigh region compared to the abdominal region (Pollock & Wilmore, 1990).
Estrogen & LipolysisThe female hormone estrogen may have a positive effect on resting and exercise fat metabolism. Although there appears to be a connection between estrogen and increased fat metabolism, the mechanisms are not fully understood. Research has suggested that estrogen may aid in the mobilization of fat from adipose tissue. There are several proposed mechanisms for this increase in fat mobilization. First estrogen has been found to inhibit the hormone LPL (Ashley et al., 2000). Remember that LPL is responsible for the breakdown of TG in the blood stream for storage in adipose tissue or fuel for active tissues. Second, estrogen has been shown to enhance epinephrine production. A higher concentration of epinephrine would increase the activity of HSL, the hormone responsible for adipose tissue lipolysis.

Estrogen has also been reported to stimulate the production of growth hormone (GH). Growth hormone inhibits the uptake of glucose (carbohydrate) by active tissues and increases the mobilization of FFA from adipose tissue (Robergs & Roberts, 1997). GH works by inhibiting insulin production from the pancreas and stimulating HSL (Ashley et al., 2000). Insulin is the main hormone that promotes glucose transport into muscle cells to be used as energy, and it is a potent inhibitor of HSL. Estrogen may enhance fat metabolism by increasing the production of GH and inhibiting the production of insulin. In turn, this would decrease glucose metabolism and increase FFA utilization (Ashley et al., 2000).

Another factor that could promote a higher fat metabolism in women is an increase in blood flow to adipose tissue, especially during exercise (Braun & Horton, 2001). Estrogen has been shown to cause a vasodilation (widening) in blood vessels, but it is not yet known if this vasodilation is specific to adipose tissue perfusion (flow of blood into the tissue) or a general effect on the entire vasculature in the body. Estrogen also increases the production of the hormone Nitric Oxide (NO). NO, which is produced by cells that line the blood vessels, causes a relaxation of the smooth muscle that surrounds blood vessels leading to vasodilation. If women maintained a higher blood flow to the adipose tissue, interaction between epinephrine and adipose tissue beta receptors would be increased. Additionally, this could enhance FFA transport from adipose tissue to active muscles during exercise.
Fat Metabolism at RestThe level of fat metabolism at rest is positively correlated with the size of fat cells in the body, with larger fat cells having a higher lipolytic (causing TG splitting) activity (Blaak, 2001). In earlier research it was hypothesized that women may have a higher resting fat metabolism due to typically higher body fat stores when compared to men. However, recent research has found that resting fat metabolism (adjusted for differences in lean body mass) is actually lower in women than in men (Nagy et al., 1996; Toth et al., 1998). Although the mechanisms are unclear, this finding suggests that a lower resting fat metabolism may contribute to the increased fat storage in women as compared with men.
Fat Metabolism During Exercise Intramuscular triglycerides (IMTG) are an important source of fuel during moderate to high intensity exercise. It’s estimated that up to 50% of fat oxidized during moderate to intense exercise is derived from IMTG (Robergs & Roberts, 1997; Coyle, 1995). The majority of the rest comes from adipose tissue and the least comes from TG in the blood stream. The process of IMTG lipolysis is similar to adipose tissue lipolysis. During exercise, increasing levels of epinephrine activate HSL to begin IMTG breakdown. The FFA molecules that are released from IMTG are located within the muscle cell, therefore, they can be transported directly to the mitochondria for oxidation. The glycerol molecule released is either transported to the liver for oxidation or recycled to form additional IMTG stores (Robergs & Roberts, 1997).

The majority of the research shows that women derive a greater proportion of their energy expenditure from fats during low to moderate intensity exercise, relative to men. Research is still discerning the possible mechanisms leading to these gender differences.
Gender Differences in Fuel SelectionOne of the most common methods used to determine fuel selection is the respiratory exchange ratio (RER). The RER is a numeric index of carbohydrate and fat utilization based on a ratio of carbon dioxide produced to oxygen consumed. A lower RER is an indication of a greater fat metabolism, whereas a higher RER is an indication of a greater carbohydrate metabolism. Current studies show that during low to moderate intensity exercise women maintain a lower RER when compared to men. In a study by Tarnopolsky et al. (1990), male and female subjects were matched for training status and performance experience. These researchers reported significant gender differences in RER values during moderate intensity exercise. Throughout the 90 minute run at 65% VO2max, females had significantly lower RER values compared with males, indicating an increased reliance on fats as fuel. The calculated energy expenditure (EE) from fat was 428.4 kcals for the women (42% of total EE) and 242.1 kcals for the men (20% of total EE) (See Figure 1). This data was supported by the muscle biopsy data that showed greater muscle glycogen depletion in male subjects when compared to female subjects. In a similar study by Horton and colleagues (1998) significant gender-based differences in fat metabolism during exercise were also reported. Women had significantly lower RER values compared with men during 2 hours of exercise at 40% VO2max. The percent of fat metabolized during exercise averaged 43.7% for the men and 50.9% for the women. Blatchford and colleagues (1985) studied gender differences in fat metabolism during 90 minutes of treadmill walking at 35% VO2max in untrained men and women. Women had significantly lower RER values compared with men at both 45 and 90 minutes of exercise. Both groups gradually increased the percent of fat metabolized during exercise, with the 90-minute values being 59% for the men and 73% for the women.

Froberg & Pedersen (1984) reported that women subjects exercised for a significantly longer period of time than age- and training-matched male subjects at 80% VO2 max. The women also had significantly lower RER values during exercise when compared to the men. These researchers concluded that the greater performance in women was due to a greater reliance on fats as fuel during exercise and a sparing of muscle glycogen.
What Exercise Intensity Burns the Most Fat?During low intensity exercise the majority of energy (kcals) comes from fat. As exercise intensity increases, the percent of energy derived from fat decreases. However, the absolute amount of energy derived from fat is actually increased! As exercise intensity increases, so does total energy expenditure (caloric expenditure). Even though a smaller percentage of the energy expenditure is coming from fat, more kcals of fat are burned because there is a greater absolute energy expenditure. Therefore, expressing energy derived from fat as a percentage of energy expenditure without considering the total energy expenditure is misleading.

Another consideration is the effect that exercise has on energy expenditure after exercise. Following a high intensity exercise bout, the rate of metabolism is elevated for a slightly longer period of time (when compared to a lower exercise bout), and more energy is expended as your body returns to homeostasis (resting conditions). With regular aerobic exercise, this post-exercise energy expenditure will positively contribute to weight loss goals.
Gender Differences in Muscle Glycogen DepletionMuscle glycogen concentration is another common technique used to determine fuel utilization during exercise. Muscle glycogen is the storage form of carbohydrate that is located within the muscle cells. Tarnopolsky and others (1990) compared the muscle glycogen depletion patterns of both trained males and females (matched for training status and performance experience) during a 90-minute run at 65% VO2 max. Although muscle glycogen levels were similar between males and females prior to the exercise bout, post exercise biopsy (removing of tissue for analysis) data indicated a significant difference between genders. Glycogen depletion was 25% greater in males compared with females. This was in agreement with the lower RER data reported for females, indicating a greater reliance on fats as fuel during submaximal exercise.
Gender Differences in Epinephrine ConcentrationsStudies examining the hormonal responses to exercise have reported greater epinephrine concentrations during submaximal exercise in men when compared to women. Assuming a lower RER response in women during exercise, these findings indicate that women may be more sensitive to the lipolytic actions of epinephrine and are able to metabolize fat more effectively. Tarnopolsky et al. (1990) reported lower epinephrine concentrations during submaximal exercise in females when compared to equally trained males. This was in addition to lower RER values during exercise and less glycogen depletion post exercise in females. Horton and colleagues (1998) also reported that epinephrine levels were significantly lower in women than in men during exercise at 40% VO2max, again suggesting a greater sensitivity to the lipolytic action of epinephrine in women.
Gender Differences in Free Fatty Acid and Glycerol ConcentrationsPlasma (fluid portion of blood) concentrations of FFA and glycerol are both indicators of adipose tissue lipolysis. As adipose tissue lipolysis increases, plasma concentrations of FFA and glycerol increase. Several investigators have studied the gender differences in plasma FFA and glycerol concentrations, in response to submaximal exercise. Blatchford et al. (1985) reported significant gender differences in FFA and glycerol concentrations when males and females (matched for training status) exercised at 35% VO2max. At both 45 and 90 minutes of exercise, plasma FFA values were higher in females than in males. In addition, at 45 minutes plasma glycerol levels were significantly higher in females than in males. Horton and colleagues (1998) also found significant gender-based differences in FFA and glycerol concentrations during exercise. Plasma FFA and glycerol concentrations were reportedly higher in females than in males during submaximal exercise.

Tarnopolsky et al. (1990) reported significantly lower RER values in females during exercise at 65% VO2 max, however, this was not accompanied by an increase in plasma concentration of FFA or glycerol in these subjects. These researchers hypothesized that the increase in fat metabolism in women was due to a higher utilization of IMTG (which do not increase plasma concentrations of FFA or glycerol), as opposed to a greater adipose tissue lipolysis. The above findings on gender differences in FFA and glycerol concentrations indicate that, in women, beta receptor sensitivity for lipolysis may be increased, alpha receptor sensitivity may be decreased, or IMTG contribute to a higher percentage of fat metabolism during exercise.

In addition to the above findings, it has been reported that IMTG stores are higher in women than in men (Blaak, 2001; Braun & Horton, 2001). This finding suggests the possibility that a higher IMTG oxidation may contribute to the increased fat oxidation and glycogen sparing in women during exercise. It has also been reported that women have a higher expression of FFA transport proteins (FATP, FABP, FAT) in skeletal muscle cells (Blaak, 2001). With an increase in FFA transport proteins the amount of FFA entering the muscle cell is augmented and the FFA available for oxidation in the mitochondria (organelle of cell responsible for energy production) is increased. An increase in FFA transport into the muscle cell could also contribute to an increased FFA storage into IMTG.
The Bottom LineThere are distinct differences in the mobilization, metabolism, and storage of fat between genders (summarized in Table 1). Most of the current research is finding that the proportion of energy derived from fat is increased during low to moderate intensity exercise in women as compared to men. Although there is a handful of research on this topic, additional research is needed to determine the exact mechanisms involved in this difference between genders and why the increase in fat metabolism is evident during exercise but not at rest. Differences in percent body fat, distribution of body fat, hormonal responses to exercise, and hormone receptor type and sensitivity may all contribute to gender-related differences in fat metabolism.
New Implications for Designing Aerobic Exercise ProgramsOften times a review of literature will uncover fresh findings, introduce new ideas for research, or indicate modern opportunities for practical application. From this review on gender differences in fat metabolism, some cardiorespiratory training implications for optimal fat metabolism are presented.

The foundational research on the development and maintenance of cardiorespiratory fitness recommends performing endurance exercise, 3 to 5 days per week, on an exercise mode that involves the major muscles groups (in a rhythmic nature) for a prolonged time period (ACSM 2000). This includes physical activities such as step aerobics, aqua exercise, cardio kick-boxing, rowing and walking. The ACSM recommends an intensity of exercise between 55/65% to 90% of maximum heart rate (or 40/50% to 85% of oxygen uptake reserve), with a continuous duration of 20 to 60 minutes per session. Inherent in the exercise prescription is the concept of individualizing the program for each person’s fitness level, health, age, personal goals, risk factor profile, medications, behavioral characteristics, and individual preferences. The ACSM recommendations appropriately serve as the framework for the cardiorespiratory fitness prescription for healthy males and females that follows.

Expounding from this review of literature, it appears a contemporary approach, with regards to fat metabolism, may be suggested. Initially, the concept of periodizing aerobic training programs, that has become so popular in resistance training, is advocated. Periodization training is based on an inverse relationship between intensity (how hard) and volume (total repetitions) of training (Stone et al, 1999). With aerobic exercise, intensity can be individualized with %heart rate max, %VO2 max, or ratings of perceived exertion, where as volume is differentiated by the duration of the session, as well as the frequency of sessions.
Here are some specific periodization suggestions from which to individualize the prescription for optimizing fat metabolism, during aerobic exercise:1) Regularly incorporate cardiorespiratory workouts that are low intensity for a longer duration. Rationale: The majority of the research shows that women derive a greater proportion of their energy expenditure from fats during low to moderate intensity exercise, relative to men. Thus, this will improve fat metabolism, particularly for females.
2) Incorporate some cardiorespiratory workouts that are of higher intensity for a shorter period of time. This may best be realized with high intensity continuous training or perhaps with interval training. Rationale: As exercise intensity increases, the percent of energy derived from fat decreases. However, the absolute amount of energy derived from fat is actually increased, for males and females. As exercise intensity increases, so does total energy expenditure (caloric expenditure). Even though a smaller percentage of the energy expenditure is coming from fat, more kcals of fat are burned, because there is a greater absolute energy expenditure.
3) Incorporate various modes of training, often referred to as cross-training (Kravitz & Vella, 2002). Rationale: The theory of multi-mode training implies that by training on different modes of exercise, the body is averted from getting overly fatigued and from overuse of the same muscles in the same movement patterns. This helps to thwart the occurrence of musculoskeletal system stress, aiding in the prevention of muscle soreness and injuries. Therefore, theoretically, a person will be able to safely do more work, more frequently, which equates to higher total energy expenditure and fat utilization.
4) Vary the above workout designs regularly! Endeavor to find a satisfactory method for each client, or students in a group-led class, where cardiorespirtory workouts vary either within each week, weekly, bi-weekly, or any combination of all. Rationale: Similar to the above, varying the workouts provides a new stimulus to the body’s cardiorespiratory system in an effort to avoid the consequences of overuse exercise fatigue.
Adipose Tissue InformationAdipose tissue is a form of connective tissue composed of cells (adipocytes) that are separated by a matrix of collagenous and elastic fibers. Body fat accumulates by filling existing adipocytes causing an increase in size (hypertrophy) and by the formation of new fat cells (hyperplasia). Normally, fat stores increase from birth to maturity by a combination of hypertrophy and hyperplasia. Obese adults typically have 60 to 100 billion fat cells, compared with 30 to 50 billion for non-obese adults (Pollock & Willmore, 1990). Early research indicated that fat cell number increased markedly during the first year of life, increased gradually until puberty, and then increased markedly again for a period of several years, with the maximum number of cells becoming fixed by adulthood. Current evidence suggests that fat cell size and number can be increased at any age. The exact mechanism for hyperplasia is still unknown, however, it is hypothesized that fat cells have a certain capacity and once that capacity is reached a new cell will be formed (Pollock & Willmore, 1990). Interestingly, fat cells can increase or decrease in size, but once a fat cell develops it is a permanent cell in your body, except for way of liposuction.

ReferencesAmerican College of Sports Medicine. 2000. ACSM’s Guidelines for Exercise Testing and Prescription, 6th Edition. Philadelphia: Lippincott Williams and Wilkins.
Ashley, C.D., Kramer, M.L., & Bishop, P. 2000. Estrogen and Substrate Metabolism. Sports Medicine, 29(4), 221-227.
Blaak, E. 2001. Gender differences in fat metabolism. Current Opinion in Clinical Nutrition & Metabolic Care, 4, 499-502.
Blair, S. 2002. The public health problem of increasing prevalence rates of obesity and what should be done about it. Mayo Clinic Proceedings, 77,109-113.
Braun, B., & Horton, T. 2001. Endocrine regulation of exercise substrate utilization in women compared to men. Exercise & Sports Science Reviews, 29(4), 149-154.
Blatchford, F.K., Knowlton, R.G., & Schneider, D.A. 1985. Plasma FFA responses to prolonged walking in untrained men and women. European Journal of Applied Physiology, 53, 343-347.
Coyle, E.F. 1995. Fat metabolism during exercise. Sports Science Exchange, 8(6), article 59.
Frogerg, K., & Pedersen, P.K. 1984. Sex differences in endurance capacity and metabolic response to prolonged, heavy exercise. European Journal of Applied Physiology, 52, 446-450.
Horton, T.J., Pagliassotti, M.J., Hobbs, K. & Hill, J.O. 1998. Fuel metabolism in men and women during and after long-duration exercise. Journal of Applied Physiology, 85(5), 1823-1832.
Kravitz, L. & Vella, C.A. 2002. Energy expenditure in different modes of exercise. American College of Sports Medicine Current Comment, June, www.acsm.org.
National Heart, Lung, and Blood Institute. 2002. Obesity Education Initiative, www.nhlbi.nih.gov.
Nagy, T.R., Goran, M.I., Weisnsier, R.L. 1996. Determinants of basal fat oxidation in healthy Caucasians. Journal of Applied Physiology, 80, 1743-1748.
Pollock, M.L., & Wilmore, J.H. 1990. Exercise in Health and Disease, 2nd edition. (pp. 61-82) Philadelphia: W.B. Saunders Company.
Robergs, R.A., & Roberts, S.O. 1997. Exercise Physiology: Exercise, Performance, & Clinical Applications. Boston: WCB McGraw-Hill.
Rasmussen, B.B., & Wolfe, R.R. 1999. Regulation of fatty acid oxidation in skeletal muscle. Annual Reviews in Nutrition, 19, 463-484.
Tarnopolsky, L.J., MacDougall, J.D., Atkinson, S.A., Tarnopolsky, M.A., & Sutton, J.R. 1990. Gender differences in substrate for endurance exercise. Journal of Applied Physiology, 68(1), 302-308.
Stone, M.H, Pierce, K.C., Haff, G.G, Koch, A.J., & Stone, M. 1999. Periodization: Effects of manipulation of volume and intensity. Part 1. Strength and Conditioning Journal, 21, 56-62.
Toth, M.J., Gardner, A.W., Arciero, P.J., Calles-Escandon, J. & Poehlman, E.T. 1998. Gender differences in fat oxidation and sympathetic nervous system activity at rest and during submaximal exercise in older individuals. Clinical Science, 95, 59-66.

Agar Diet

By Norma Chew

Agar has been used in Asian cooking for hundreds of years. Agar comes from seaweed that grows on the rocky areas of tidal waters of Japan, China and Sri Lanka. Agar is white and semi-translucent; it's void of sugar, starch, soy, corn, gluten, yeast, wheat, milk, egg, animal byproducts or preservatives, according to VegetarianLoveToKnow.com. It's a vegetarian delight, available in dried strips, powdered form or as flakes. As with any dietary supplement, agar should be taken with the advice and supervision of your health care practitioner.

Uses

According to Michele Wanke, of VegetarianLoveToKnow.com, agar is used as a filler in paper sizing fabric as well as a clarifying agent in brewing. It's also used as a dietary supplement to lose weight. It is commonly used as a thickener for soups, jelly and ice cream, as well as a binder in puddings and custards.

Nutritional Value

According to QuiteHealthy.com, a 1-ounce serving size, or 28 grams, of agar contains 0.9 grams of total fat, 87 calories, 22.93 grams of carbohydrate and 1.76 grams of protein. The mineral content in this serving size includes 177.19 milligrams of calcium, 318.84 mg potassium, 6.07 mg iron and 28.92 mg of sodium. Agar contains no cholesterol.

Benefits

Agar acts as an appetite suppressant; it becomes gelatinous when wet, swells and gives a feeling of fullness. This suppresses your hunger, curbs your appetite and promotes weight loss. It's a rich source of minerals. It's a high-fiber product with a laxative effect that helps to regulate and cleanse the bowel.

Research

A study by Hiromichi Maeda, et al evaluated the efficacy of the combination of an agar diet with a conventional Japanese diet for obese patients with glucose intolerance and type 2 diabetes. The results were published in 2005 in the Diabetes Obese Metabolism Journal. Seventy-six patients were randomly assigned a conventional diet or a conventional diet with agar for 12 weeks. Both groups' body weight, body fat, fat distribution, body mass index, glycemic control, blood pressure, insulin resistance and fat and lipids were measured before and after the experimental period.

The results revealed that the agar diet produced significant weight loss due to maintenance of reduced calorie intake and improved metabolism.

Considerations

Agar is a bulk laxative that may influence dietary absorption of minerals, protein and fat, according to the Ayurvedic Medicine website. Take agar on an empty stomach with at least 8 ounces of water. Follow up with adequate fluid intake throughout the day to avoid the side effects of bowel or esophageal obstructions. Agar should not be taken during pregnancy or while breastfeeding. Discuss any medications you are taking with your
doctor before taking agar.

Comments

Agar is largely composed of carbohydrates that we can not digest. So contributes very little glucose in the blood.. It can be used a filler because it gels so absorbs a lot of water. You can include a little in the diet as a very low calorie food. It is best to hydrate agar if you take it as a supplement.

How to get fit if you’re starting from scratch

Posted by Samantha Clayton, AFAA, ISS

Do you exercise enough? Do you wish you were more fit but days and weeks slide by without you doing anything active?

Despite best intentions, all of us can get caught in a no-exercise rut. We have busy lives and fitness sometimes slips down the priority list. Unfortunately, for some, it can seem like you’re so far out of shape that you’ll never get fit again.

I’m here to tell you that you can get fit again. No matter your current fitness level, today’s fitness advice may help.

I’ve gone back to basics and focused on what really helped me. There was a time when I didn’t feel great about my body and I lacked stamina, strength and flexibility. My self-confidence dipped and I wanted to hide – I couldn’t believe that I’d let myself fall so far and regaining my former fitness felt like a mountain too steep to try and climb.

This isn’t the usual fitness article about how you need xx minutes of this exercise and xx minutes of that exercise. This is designed for those of you who sincerely want to get fit and don’t know where to start because, right now, all exercise feels too daunting to even try. Don’t despair – I’m here to give you fitness hope,

My ‘3 x ABC’ get fit program

Using my own experience of adjusting to life with four children and a husband who was always traveling for work, these are my ABCs to help you get back on track. Give these tips a go and you could find yourself back in possession of willpower, confidence and energy in no time!

Fitness AAA

A = Action

Fitness and exercise can feel like too big a challenge, so let’s just push to become more active. That can mean adding in a simple stretch or a walk around the block. Any movement is better than no movement.

If you’re not fit then you don’t need any high-pressure labels, so let’s simply take ‘action’ by being ‘active’ in some way every day.

A = Analyze

Look at your schedule and see where there is time for action. You don’t think you have two hours to get to the gym, change, workout, change and get home again? Fine. Let’s start small. Can you find a minute before breakfast or two minutes after work?

Just as you wouldn’t start climbing a mountain at breakneck speed – you can slowly ease yourself into action. Find a few minutes and use them to stretch. Reach to the ceiling or gently roll your neck and enjoy the feeling. Overtime, try to build from two minutes of action to five.

A= Accountability

You know you need to exercise. I know you need to exercise. Add it to your daily to-do list and do something active every day.

If you stretch before breakfast for a minute, then write it down. If you walk to the end of your street, then write it down. You’re more likely to exercise if you hold yourself accountable and after five days you’ll have at least five minutes of exercise to show for it.

You might not be at the top of the mountain yet but you can see you’ve made a start!

Fitness BBB

B = Breathe

For me, my falling fitness level was tied to an increasingly busy lifestyle and stress. That taught me that it’s good to make time to breathe.

Right now, as you’re reading this, take a deep breath in and feel your chest swell. Now breathe out slowly; try to push all the air out of your lungs.

Mindful breathing can help us focus so find something you do every day and use it as a reminder to enjoy some relaxing deep-breathing. You might decide to deep-breathe while waiting for the coffee to brew or as you water your plants. I do it after the kids clamber out of the car for school and I have a moment before driving away and tackling the next part of my day.

You won’t get far up that mountain if you don’t take time to breathe and assess your progress.

B= Break

Take a break. We’re all busy and it feels like we just don’t have any time but are you sure you can’t squeeze in a five minute break from what you’re doing? Hard as it might be to believe, your productivity may go up if you step away for a moment. A break to walk from one side of the room to the other, or to step outside can help you refocus while adding crucial action moments to your day.

And if you do take a moment to walk around your place of work then don’t forget to write it down. Every step takes you a little higher up that fitness mountain.

B = Balance

You’re more likely to stick with your daily actions if you can find a way to balance your new activities with your daily needs. You still need to do your chores, keep up your social circle and all the other things that make up your day-to-day life. No one wants to be boring so find the right life balance. That means you need to add more action than you were doing but don’t go over the top and become so active that it’s unsustainable.

To get all the way up that fitness mountain, you need to pace yourself.

Fitness CCC

C= Change

Change won’t happen unless you make it. We can all wish and hope and dream but we won’t get fit unless we take a first action step.

You have to be honest with yourself every day. If a day goes by and you haven’t had an action moment then understand that you aren’t climbing the mountain; you’re standing still or even rolling back down.

C= Community

Use your community to help you rebuild your fitness. Your family, friends and co-workers can help you clock-up action moments and may want to join you as you steadily climb the mountain. You probably aren’t the only person you know who wants to be more fit. Tell everybody what you’re trying to do and you’re friends will motivate you. They’re likely to be proud of you for actively taking back control.

Climbing that mountain is easier if you aren’t struggling up alone.

C = Commit

None of my ABCs will help if you don’t commit to taking action. As you read this, I hope you feel motivated. Use that feeling right now: move your body in some way: stretch you arms out or take a deep breath and point your toes. If you’re feeling really motivated then do a little wiggle and feel yourself smile…

Now that you’ve started, commit to taking a few more steps up the mountain each day. Pretty soon you’ll look back and see how far you’ve climbed.

Written by Samantha Clayton, AFAA, ISSA. Samantha is Director of Fitness Education at Herbalife.

Belly Laugh At Least Once A Day

One Wild Life ~ Belly Laugh At Least Once A Day

by SHELLI JOHNSON 

“Our most effective weapon is laughter.” ~Mark Twain

I started belly laughing daily when I did the Encourage Yourself 21-Day Challenge. I keep it up now because it makes me feel better.

According to many medical centers (including the Mayo Clinic & the University of Maryland, their research quoted here), laughter is great for your health. Here are 7 reasons that you should do whatever you need to do to belly laugh at least once every day:

Belly Laughter:

• Decreases the stress hormones cortisol and epinephrine.
• Balances (lower/raise depending on your body) blood pressure & improves blood circulation.
• Relaxes muscles which in turn helps your whole body & mind to relax.
• Helps open up airways and increases oxygen intake (because you take deeper breaths when you’re belly laughing).
• Acts as a natural pain reliever by releasing endorphins (hormones that increase our feeling of well-being & help with pain management).
• Improves immune system function by increasing the level of antibodies within you that fight bacteria & infection.
• Connects you with other people because it’s a universal language that puts people at ease & that everyone understands.

So do you belly laugh at least once a day? If not, start today!

Top 10: Reasons You Don't Have Abs

by Shannon Clark

f there's one fitness goal that almost every man goes to the gym in hopes of achieving, it's a ripped set of abs.

Whether you're trimming down or developing more muscle mass, there's no question that your abs are important. But you might have worked on sculpting an eye-catching stomach many times in the past without ever seeing the results you had hoped for. What is it that makes getting ripped abs so hard to achieve?

Let's take a look at the top 10 reasons you don't have abs.

1/You have low muscle tone
The first reason you don't have abs is simple: a shortage of muscle. While everyone has a degree of abdominal development, some people simply have very little of it. The larger your ab muscles are, the more the definition of the muscle will be able to show through your body fat, and therefore, the more ripped you'll look. Start performing heavy-weighted ab work to overcome this problem. Weighted decline sit-ups work perfectly.

2/It's not in your genes
Another reason you don’t have abs is that you simply don't have the genetics for it. Some people are naturally prone to carrying more abdominal fat, and even if they get down to leaner levels with ripped arms and legs, the abs still don't show through. Couple that with the fact that genetics plays a principal role in determining the shape of the abs and the way they look on the body, and you'll realize that if you have genetics working against you, toning your abs is going to be an uphill battle.

3/You're not drinking enough water
In today's world of fast food and excessively processed foods, water retention is the norm. If you have a high-sodium diet and you're not drinking enough water throughout the day, you can bet your looks will be hindered by what you consume. Up your water intake to at least 10 glasses a day and put down the saltshaker. You'll see noticeable differences in two to three days' time.

4/You're not sleeping enough
Do you find yourself staying late at work and vowing to sleep in on the weekend to make up for it? If you're hoping for six-pack abs, you'll have to rethink that strategy. Lack of sleep causes increased cortisol to surge through your system, and this potent hormone actually encourages the accumulation of stomach fat. Get to bed earlier. Not only will you see belly benefits because of it, but you'll be more productive during the day so you won't have to stay so late in the first place.

5/You need more carbs
If you're like many people, you think removing the carbs from your plate is the fastest way to get lean. Unfortunately, that's often not the case. Low-carb diets may be useful for fat loss, but following a very low-carb diet for a long time will cause you nothing but problems. Certain fat-fighting hormones begin to change when your carb intake is too low, and this actually causes your metabolism to shut down. When your metabolism slows, you end up burning so few calories over the course of the day that fat loss becomes next to impossible. Go high-carb once a week to keep the balance steady. Your abs will thank you.

6/You're too focused on abs
Some men who have a six-pack as their goal focus the greater part of their workout on training the abdominal muscle group. Sadly, this focus only drives them further away from their goal. Since the ab muscles are very small, they're hardly going to burn any calories at all (per minute of exercise). Instead, try to focus on compound movements. These work the abs in the course of greater stabilisation exercises, and in the process they burn 10 times the calories any crunch will.

7/Your have poor abdominal control
Abdominal control doesn't end when you finish a workout. If you train your abs hard in the gym but then let them relax the rest of the day, you're making a critical error. Instead, focus on keeping them tight and pulled in at all times. Eventually it will become a habit and you'll immediately look leaner.

8/You drink too much
Headed out for another Friday night with the fellas? Before you order another beer at half-time, think about its effect on your six-pack goal. As soon as it enters the body, alcohol immediately puts the brakes on fat loss, which means each beer really slows down your progress. Drinking too much too often can also encourage fat to develop around the stomach area, making your job that much harder. While you may take some ribbing when you ask for water, you'll render your buddies speechless next time you cross paths with them at the gym.

9/You're too stressed
Just like lack of sleep, high levels of stress also induce the release of cortisol and quickly cause fat gain in the belly area. If you lead a high-stress lifestyle and feel chronic tension, not only are you encouraging stomach fat accumulation, but you're also risking the loss of lean muscle-mass. If you want to stay ripped everywhere else and move closer to a six-pack, you must control your stress.

10/You binge eat
Even the best of us crack under the pressure of too long on a strict diet. If you're trying to stick with a regime far too low in calories and carbs, it won't be long before you hit the buffet with a vengeance. When binge eating rears its head in your diet plan, have a good look at the regimen you're following and be sure you're consuming enough calories. A very low-calorie diet is the chief reason why most men binge. Your intake must be appropriate to your size and activity level. Low calorie is good, but too few calories will leave you hungry for a binge.

Low-Carb Thickeners

How To Thicken a Low-Carb Sauce

By Laura Dolson

When making a white sauce or other sauce, stew, or soup requiring a thickener, many low carb cooks are unsure of the best approach, since traditional thickeners are starches. Sometimes if you are only using a little starch for a recipe that makes several servings, it may not matter. However, if you are cooking a thick sauce or soup, you might want to consider some lower carb alternatives. Here are some of the ins and outs of sauce thickeners. Feel free to mix and match according to the effect and carb level you are going for.

Traditional Starch Thickeners

Regular Flour - White flour is the most common thickener used in sauces. In some recipes, you might be fine using it. There are 6 grams of carbohydrate per tablespoon of regular flour. This will thicken one cup of a gravy (which has some thickeners from the meat), or a thin sauce. It takes two tablespoons of flour to thicken a sauce of medium thickness, and three for a thick sauce. Whole wheat flour has 4.5 grams effective carbohydrate plus 1 gram fiber per tablespoon. It takes slightly more to thicken a sauce than white flour.

When you use flour to thicken a sauce, you can't add it directly, as it will create lumps. The best way to add it is in a roux, where you heat it with a fat like oil or butter and cook it for a minute or two (stirring constantly) to get rid of the raw flour taste. Then whisk in the liquid. A roux will slowly get darker the longer you cook it, and some recipes will call for darker rouxs, however, their thickening power decreases as you cook them, so for low carb purposes, a white roux is best.

Other ways to add flour to a sauce are a slurry, where you stir or shake up the flour with cold water and then add to the sauce, or a beurre manié, where you mix the flour and butter into a paste and add it bit by bit. You can also add the flour to vegetables or meat as you are browning or sauteing them.

Cornstarch - Cornstarch has 7 grams of carb per tablespoon, but more thickening power. According to the corn starch manufacturers you only need half as much cornstarch as flour, but experts seem to vary on this point. Sauces thickened with cornstarch are less opaque and glossier. Cornstarch is generally added to cold water and then to the sauce. You don't have to worry about cooking it first.

Arrowroot - Arrowroot is similar to cornstarch and used the same way, except it makes a totally clear sauce and lends a glossier appearance. Stands up to acidic liquids better than cornstarch.

Making a Low-Carb White Sauce

To make a low-carb white sauce (Bechamel sauce), you can use any dairy product, or unsweetened soy or almond milk (check the ingredients carefully to make sure no sweetener is added), with any of the thickeners on this page.

Alternative Thickeners

If you want to avoid starches altogether, there are quite a few alternatives. Which one you choose will depend a lot upon what you're making.

Reduction - Simply simmering the sauce until enough water evaporates that the sauce is thicker works in some cases.

Vegetable gums - Yum! They may not sound really appetizing, but vegetable gums are just a type of fiber that absorbs water to make a sort of gel. They are often used as thickeners in commercial products. The most common are guar gum and xanthan gum, which can be purchased at most health food stores or online.

To use vegetable gums to thicken sauces, sprinkle them into the sauce while whisking. Often it only takes a small amount, so go slowly. Too much will overthicken and/or give the sauce a "slick" feel.

An alternative to plain vegetable gums are products based on them which are a little easier to use. Expert Foods makes several of these products for different uses. I particularly like the not/Starch.

Pureed vegetables - This is especially good for creamy soups, but works for other sauces as well. Almost any cooked vegetable can be blended and used to thicken a soup or sauce (think broccoli or pumpkin soup). Tomato paste is a great thickener. Eggplant, zucchini or other squash, cauliflower, or the lower carb root vegetables are all excellent choices when you don't want the vegetable to add too much flavor.

Cream - Cream will thicken as it reduces, so if you add cream to a sauce and boil it, the sauce will thicken more than reducing without the cream.

Sour cream is already thickened - whisk it into a sauce.

Cream cheese is thicker than sour cream, although it obviously has a distinctive flavor.

Butter - If you add cold butter at the end of cooking a pan sauce, it will have a thickening effect

Egg Yolk - Think of mayonnaise - at it's heart, it's nothing more than oil and egg yolk. Or think of hollandaise sauce. An egg yolk can really bring the right kind of sauce together, especially if there is oil or fat in it. Don't add the yolk directly to a hot sauce or it will scramble. To avoid this, "temper" the yolk(s) by adding a small amount of the sauce to the them to gradually bring them up to temperature. Then add the tempered eggs to the sauce.

Nuts and nut butters - Ground nuts were traditionally used to thicken sauces in olden times. Nut butters (peanut, almond, etc) work even better.

Flax seed meal - Flax seed meal does thicken liquids, but it's so grainy that I haven't found it to work well in many sauces. I like it to thicken shakes, though.

First there was the 5:2 diet, then the 2:5, then the 4:3... Where will it end?

January, and intermittent fasting is all the rage. But it's about to get even more radicalSARAH MORRISON

Eating is now a numbers game. Depending on who you listen to, you should fast for two days a week, on alternative days, or even over five consecutive days every two months, if you want to keep the weight off. But as the diets get more radical, the perfect ratio of healthy eating is proving more elusive to pin down.

It all began with the 5:2 diet, the intermittent fasting eating plan championed by everyone from Beyoncé to Alex Salmond. It struck a chord in its simplicity. For two days a week you eat only 500 calories (600 for men), and the rest of the week you eat normally.

The Fast Diet, the book which advocated the fasting plan – written by Dr Michael Mosley and Mimi Spencer – reportedly ended last year as Amazon's best-selling book. An estimated four in 10 British slimmers tried the diet.

But now, nutritionists are upping the ante. Dr Krista Varady, one of the women whose clinical trials helped to start the 5:2 fasting plan, has published a new book lauding the Every Other Day diet, or the 4:3 diet – where you fast on alternate days.

Scientists at the University of Southern California have started a clinical trial to see how eating very little for five days in cycles can affect weight and even how it could be used to manage blood pressure.

The British Nutrition Foundation is hosting a symposium on the evidence behind popular diets this week, with a whole section dedicated to "intermittent fasting". Men seem keener on the fasting plan than, say, the low-carbohydrateAtkins diet. David Ryan, 54, a journalist who has never tried a structured diet before, said he plans to start the 5:2. "It's the carrot-and-stick approach of being able to resume normal eating after each day of fasting that's appealing," he said. "It's more attractive than constantly being on a diet."

Champions of the diet claim that it can bring health benefits, including longer life expectancy, increased cognitive function and protection against conditions such as dementia. Clinical trials have suggested a reduction in the risk of developing certain obesity-related diseases, such as breast cancer. However, the NHS describes the evidence for 5:2 as "limited" and the diet as "a fairly radical approach to weight loss".

But is it just another way to encourage structured dieters – usually women – to obsess about their weight? Nutritional therapist Deborah Colson, director of the British Association for Applied Nutrition and Nutritional Therapy, is not so sure. She said the basic principle of the restriction of calories was "clearly sound". She added: "When we were hunter gatherers, we didn't have a constant supply of food. When there is a lack of food, we become sharper, with more energy to find food.

"It's not all about calories; we have to make sure what we do eat counts in nutrients. Could it be that we could [just] eat less every single day?"