Contestants on the reality television show “The Biggest Loser” exercise for hours a day and follow restricted diets to lose dozens of pounds on the show. But a longitudinal study published this week found very few of them were able to maintain their weight loss in the years following their appearances on the show. (The New York Times published a story this week on the study and the contestants experiences.)
This new study provides a window into the intricacies of weight loss, and what factors actually lead to a sustained reduction in weight.
For decades, health experts have promoted the notion that losing weight is all about calories in versus calories out. Simply burn more calories than you consume in a day, and you will become thinner. Following this guideline, it makes sense that exercising to burn additional calories is equally as effective as eating less. (If you’ve ever counted calories or tried to lose weight, you probably followed this common equation: If you maintain a 500-calorie deficit each day, you should lose about one pound each week.)
But, in fact, the evidence shows that each person’s weight is based on a much more complicated equation that depends on his or her metabolism (the number of calories the body burns at rest) and the production of hormones that trigger feelings of hunger.
Dozens of studies and several major systematic reviews show that exercise — while incredibly effective at improving overall wellness — does not actually help much with weight loss.
A systematic review published in the Obesity Reviews in 2012 explains that weight loss from exercise tends to be lower than predicted for two reasons. First, most people believe they are burning more calories through exercise than they actually do. Second, exercise triggers a hunger response that leads people to eat more that they would otherwise.
The problem is, these responses vary greatly among individuals. So while exercising may lead some people to eat more, others are able to use exercise to maintain a calorie deficit and lose weight.
A review published by Australian health researchers explains the wide range of physiological, behavioral and inherited factors that contribute to the weight loss equation. Among them are how much sleep a person gets, what type of muscle fibers they tend to carry, and whether they have “cold-climate genes” which lead the body to hold onto fat for warmth.
But while exercise may not be the holy grail of weight loss, it is really good for you. A review published in 2012 in the British Journal of Sports Medicine demonstrates that even when exercise does not lead to significant weight loss, it does lead to significant improvements in health. Exercise consistently improves aerobic capacity and lung function, reduces blood pressure and can lead to a reduction in belly fat.
Another systematic review written by researchers at Stanford and Harvard universities and published in the British Medical Journal found that exercise and drug treatment were statistically equivalent in their effects on heart disease and diabetes. In addition, there is clear evidence that exercise can improve mood and alleviate depression.
The take-home message here is clear: If your goal is to lose weight, exercise may not help you. But exercise is an essential part of improving health, fitness and wellness.