For many people, keeping weight off once they’ve lost it can be harder than shifting it in the first place. Some studies have shown that between one-third and two-thirds of dieters who lose weight regain what they lost within five years, and many end up heavier than they were when they went on the diet in the first place. Scientists have long had theories about why this happens.
Now, a US study has an explanation linked to several quirks of our biology: researchers believe that, after we’ve lost kilos, our bodies burn fewer calories, so we need to eat less if we want to maintain our lower body weight. It’s as if our bodies don’t want us to lose any more weight, so they make an effort to store calories instead of burning them.
The study shows that the muscles of people who’ve been on a diet change so that they use fewer calories to do their work. So, if you are still eating the same number of calories, you’ll actually gain weight. This message has come out of a study carried out at Columbia University in New York, where a research team has been closely monitoring dieters for years.
They put volunteers on a strict diet to shed 10% of their body weight. They then asked the subjects to do their best to maintain their weight. Tests showed that if the volunteers started eating normally, the kilos quickly piled on again. The professor in charge of the study, Michael Rosenbaum, says that to stay the same weight, you have to eat around 300 fewer calories a day than someone else who weighs the same amount, but hasn’t been on a diet.
Three hundred calories a day is roughly a medium blueberry muffin; a cup of cereal with milk and a banana; two bits of garlic bread or a standard chocolate bar. Prof Rosenbaum says his studies also show that after you’ve been on a diet, the areas of the brain that see food as a tasty reward are more active, while the areas that generate feelings of restraint are more sluggish. So you may be more tempted by unhealthy “treat” foods and also find them harder to resist.
So does this mean dieting is a complete waste of time and you shouldn’t bother? Well, if you are overweight, it is important to get down to a healthy weight for your height as this can help to prevent disease and chronic conditions. But going on a diet to reduce food intake until you reach a certain weight, only to return to pre-diet eating patterns, is not going to work long-term. You have to stick to healthy eating for the rest of your life.
