The festive season is fast approaching, and many of you may be looking to lose some weight in time for those Christmas parties, but be warned: yo-yo dieting could be the reason you can’t shed those pounds.
A collaborative study between Exeter and Bristol University, published in Evolution, Medicine and Public Health, indicated that yo-yo dieting can actually lead to an overall increase in weight. Yo-yo dieting, so called because the weight changes resemble the motion of a yo-yo, is the repeated cycling between periods of weight loss and regain. Although yo-yo dieters may experience the instant gratification of weight loss initially, they are likely to relapse and end up over-eating after a short period of time.
Many animals, such as birds, experience phases of varying food supplies, and respond to this by gaining weight between food shortages. Based on this, the researchers designed a mathematical model of an animal that undergoes periods of food shortage and abundance, and used this to observe any weight changes that occur. They determined that the body ‘learns’ if food is available consistently or if there are likely to be periods of fasting, and adjusts the amount of fat stored accordingly.
When applied to humans, the model explains how yo-yo dieting can actually cause you to pile on the pounds, as the body predicts a stage of fasting and responds accordingly. Scientists believe that the result can be explained by the ‘caveman response’. In the past, our ancestors were more likely to survive periods of famine by putting on weight when food is plentiful. But in a time of junk food and couch potatoes, the caveman response does more harm than good.
“Surprisingly, our model predicts that the average weight gain for dieters will actually be greater than those who never diet,” says Dr Andrew Higginson, Senior Lecturer in psychology at the University of Exeter. “This happens because non-dieters learn that the food supply is reliable so there is less need for the insurance of fat stores.”
Obesity is a major health problem in the developed world, with the UN Food and Agriculture Organisation estimating that nearly 25 per cent of Britons are classed as clinically obese. This figure is expected to double by 2050, and scientists and health professionals are desperately trying to find ways to get the nation to slim down.
So what’s the best way to lose weight – and keep it off? Scientists recommend you’ll have the most success by consistently eating slightly less than normal, combined with regular exercise – who would have thought it!