When DID we start getting fat?

by Roger Highfield

Theories abound to explain why our waistlines started expanding, reports Roger Highfield

The introduction of the microwave, the birth of the supermarket and the end of the Second World War are among the reasons for the current obesity epidemic, according to experts who will today debate when precisedly the nation's waistline began to expand.

The microwave oven will be blamed by Jane Wardle, Professor of Clinical Psychology, University College London.

She explains. 'Population data in the UK show that obesity rates started to rise soon after 1984, and went up steadily at just under one percentage point a year. This same period saw the rapid spread of ownership of microwaves along with the first chilled, ready-meals appearing on supermarket shelves."

Eating got steadily cheaper, quicker, and more convenient, in the home and outside increasing our tendency to overeat and gain weight.

"Most of us, most of the time, match the energy we take in to the energy we expend," she said. "But people vary in their sensitivity to internal satiety [fullness] signals, and those with low satiety sensitivity can easily slip into positive energy balance.

In fact, most obese people don't overeat by a lot, but an energy excess of only 70kcals a day - no more than a ginger biscuit - adds up to 70lbs of extra weight in 10 years; enough to turn a slim 25 year old into an obese 35 year old.'

Professor Wardle will discuss her view with Dr Susan Jebb, Professor Ken Fox, and Professor Tim Lang at the Cheltenham Science Festival today (Wed 6 June), backed by The Daily Telegraph, which runs until Sunday (10 June 2007).

'Surprisingly the experts have all chosen different years and different triggers for the start of the obesity epidemic, illustrating the complexity of this problem and the fact that solving it has to be much more than telling people to eat less, do more.' Says Vivienne Parry, broadcaster who will chair the debate.

Tim Lang, Professor of Food Policy at City University also considers the changing way we eat as key, but pinpoints an earlier date - 1948 and the introduction of the supermarket.

'The year I choose is 1948 which is when the Co-op introduced the supermarket retail format to Britain, heralding the late 20th century food revolution in which prices have tumbled, car use rocketed, physical activity plummeted, cheap calories proliferated and the epitome of modernity was a tin shed stacked with 20,000+ items, and . . . the NHS was born, which picks up the pieces.'

Ken Fox, Professor of Exercise and Health Science, University of Bristol suggests July 5 1945, which marked the end of the war and the beginning of the end of manual effort. Professor Fox explains. 'The end of the war saw technology starting to replace physical effort in both work and leisure.

The TV arrived along with cars in big numbers. We stopped walking and cycling to work in large numbers. At the same time, we could not shake off our pre war values of earning the right to put our feet up. We have dramatically reduced our daily energy expenditure in the last 60 years and we have not managed to compensate by reducing our food and drink intake. We did not see the major effects until the early 80s because it takes a while to get fat (about 20-30 years) at the rates we probably have done.'

Dr Susan Jebb of the Medical Research Council Human Nutrition Research Centre Cambridge has pinpointed a more individual basis for the problem identifying the moment of conception as the key date. 'The nutritional status of the mother and later, the choice of breast or formula milk and the volume of milk provided, set the baby on its lifetime weight trajectory,'

Says Dr Jebb. 'Later parenting practices and peer group pressure reinforce the social value of foods and gradually we each begin to make our own decisions about our lifestyle - the die is cast.'

Other experts, who are due to launch a major report on obesity in October, suggest the following:

1986
Introduction of the IBM PC & daytime television

Tom Sanders, professor of nutrition, King's College Hospital "I would argue that in the UK prevalence rates started to increase across age groups in the 1980s. This was the time when day time TV started (BBC 1986, ITV 1987) and also the advent of the PC era with the debut of the IBM PC in 1981. The acceleration of obesity has been aided by Microsoft Windows."

1975
The advent of fast food outlets

Professor Peter Kopelmann, Dean Faculty of Health, University of East Anglia " Despite the inflationary spiral, both petrol and food costs remained relatively cheap. Car purchasing accelerated in the 1970s with many more homes acquiring either their first or second car, and we witnessed (in the UK) the advent of fast food outlets, initially the Wimpy but latterly McDonalds. My obesity research began in 1978 when the condition was relatively uncommon. When asked at the Hammersmith what my research interest was, my response of obesity was greeted with incredulity - "you must be crazy" Ah well, still "crazy after all these years"!

1947
The introduction of the Agriculture Act

Catherine Law, Centre for Paediatric Epidemiology and Biostatistics, Institute for Child Health "This was the year of 1947 Agriculture Act, the first UK policy to support subsidies and encourage mass production. It coincided with the postwar Baby Boom and a massive decline in breastfeeding rates. So a (large) generation of babies grew up without the protective effects of breastfeeding and with an (over) abundant food supply.

1954
The year commercial television began

Greg Maio, professor of psychology, University of Cardiff "This year began the trend of television being present in most UK homes and available most hours of the day. By the 1960s, this level of penetration coincided with a reduction of social and leisure pursuits, an increase in snack consumption and availability, and tipped the balance toward the "energy in" side of the obesity equation."