Years of dieting have irreparably damaged your metabolism and as a result, you’ll never be as slim as you’d like. Or at least, that’s what a number of doom-mongers would have you believe.
In 1984, Geoffrey Cannon published his bestselling book Dieting makes you fat. It sold so well that he re-wrote it and in 2009 released an updated version. Mr Cannon’s claim has become something of an internet meme: the more you restrict your food intake, the likelier you are to get fat in the future. If you loose weight by dieting, you’ll put it all back on, and more, when you stop. There are different explanations for why this paradoxical effect might happen. But regardless, a quick look at the scientific literature suggests it does seem to happen.
A number of studies have been designed to test whether dieting really does lead to subsequent weight gain. For example, Dr Eric Stice and colleagues of the University of Texas at Austin recruited 692 adolescent girls and asked whether they were currently making active efforts to loose weight. The researchers followed up their participants for four years and found that on average, those who had initially reported deliberate attempts at weight loss were now heavier than before.
Why does it look that way in observational studies? It’s more likely to be due to the paradoxical cognitive effects of restrained eating. More on that later.