We often hear people on the Fatosphere mention “set point theory” or their set point when talking about why weight loss doesn’t work for most people. This can be a very confusing term. I thought I would explain MY understanding of set point theory, one I have come to after reading the experts, interviewing Fatosphere participants and my own experiences with weight loss and gain.
Set point theory suggests that our body has a particular range of weight that it is comfortable in, usually about 10% of a body’s weight. That means, if you weight 175, you have about an 18 pound range; if you weigh 325, you have about a 33 pound range. Most people lose and gain within this set point on a pretty regular basis. They may put on a little weight in the winter and lose it in the spring. Or get busy and drop a little weight. Or gain a little when stressed. Or lose a little during an illness. Or whatever. Movement within this range is normal. However, movement outside of that range is not. In fact the body seeks homeostasis – that is the body seeks to stay within that range. To move outside of that range something must go on, something must happen to the body.
This range appears to be set by a number of factors. The strongest factor seems to be genetic, as a number of studies have found. In fact, adoption and twin studies have determined that about 75% of us have the body size we do because of genetics. For that other 25%, a number of factors can mess with your set point, moving it either up or down. Disease is one of those factors. For instance, there exists a great deal of evidence suggesting diabetes causes individuals to get fat. Thyroid disease, Cushing’s Disease, PCOS and other diseases all cause weight gain. Medications can cause weight gain or loss. Depression can also cause the body to gain or lose weight. Stress can cause gain or loss. And, the kicker, DIETING can also mess with this homeostasis – increasing body weight the majority of the time.
When something tries to change the weight of an individual, the body fights back. This is true of both up and down. In the Vermot Prison study (1964) when researchers overfed prisoners, they found that the prisoners gained about 15%-25% of their body weight, then their metabolism shifted so that they could gain no more. One guy was eating 10,000 calories a day just to maintain that gain. When they quit eating so much, the majority returned to their original weight.
When we try to lose weight, the body will let it happen for a time, but then it starts fighting back. It starts adjusting the metabolism to hold onto weight. It starts an almost voracious desire for high carb and high fat foods. And the kicker, most bodies will increase the set point range, believing that it has experienced starvation and must protect against such danger again.
My own personal opinion: for 40,000 years the primary threat to the majority of humans tended to be not getting enough to eat. In fact, starvation was a strong threat until the end of World War II in the United States and is still true for some poor in the U.S. and for many inhabitants of Third World countries today. Since starvation was common, the majority of our bodies learned to hold onto weight at all costs. Any time our bodies experience lack, they learn to be more efficient in holding weight: i.e. the body that experiences lack increases the set point. Children who experience famine have very efficient bodies – bodies designed to hold onto fat. People who experience starvation repeatedly will have bodies that get better and better and holding on to fat.
So, how is the body supposed to tell the difference between starvation and a diet? It can’t. All the body knows is that the signals (signals of hunger or craving) it is sending are being ignored. And the only way it knows to respond is as if there is a famine. So it holds onto weight and creates a demand for high calorie foods. And so the diet fails for the majority of us.
Now, that is my understanding of set point theory. Any questions? Anyone else want to chime in with their own ideas about it?
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