How diet, exercise impact weight loss
Reduce calories for short-term loss, but exercise helps in the long-term
The Biggest Loser was more than a reality TV show. It was a petri dish for the study of obesity, in particular how diet and exercise impact weight loss.
The show was created with a TV audience in mind, but the research community is the biggest winner — benefiting from 17 seasons worth of contestants from which to gather data.
So far, more than a dozen studies have used the popular TV show, which debuted in 2004, to analyze the physiological and psycho-social aspects of rapid and/or significant weight loss.
The info gained is crucial in helping to understand not just how to lose weight, but also how to keep those pounds from coming back. And because The Biggest Loser focused on the eatless-exercise-more approach to dropping excess weight, it offers much-needed insight into both strategies.
Kevin Hall, senior investigator for the National Institutes of Health in Washington, D.C., has been the lead researcher on some of the more significant Biggest Loser studies. A specialist in metabolism, body composition and energy expenditure, Hall’s most current study, published in the journal Obesity, includes a team from the Veterans Affairs Medical Centre in Washington and the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Md.
Together they analyzed data obtained from 16 Biggest Loser contestants over three checkpoints: six weeks and 30 weeks into the competition, and again six years later.
So what did The Biggest Loser teach us about weight loss?
First, the intense diet and exercise regimen featured on the show worked. The 16 contestants followed by Hill and his team lost an average of 130 pounds over 30 weeks. Much of the credit for the lost weight, however, goes to eating less, not exercising more.
“Short-term weight losses were strongly correlated with changes in energy intake, suggesting that weight-loss differences were likely attributable to different degrees of energy intake reduction,” said the researchers.
Six years later, however, exercise — not diet — is credited with helping keep the weight off.
“The Biggest Loser participants who were the most successful in maintaining lost weight had the greatest increase in physical activity after six years,” reported the research group.
The amount of weight regained varied considerably among the contestants, but on average the group weighed 13 per cent less than when filming started.
Half of the group — “the maintainers” — were better than average when it came to keeping the weight off. The other half — “the retainers” — were at the other end of the scale, weighing only one per cent less than they did before taking part in the show.
How much more exercise did the weight maintainers do compared to the weight retainers?
While all of the contestants studied were more active after joining the show, those who kept the most weight off boosted their physical activity by 160 per cent compared to the retainers, whose exercise habits increased by 34 per cent. Calculated into terms most of us can understand, the weight maintainers spent 80 minutes a day performing moderate physical activity or 35 minutes daily doing vigorous activity.
The study’s findings add to the growing amount of evidence suggesting that exercise — lots of it — is crucial when it comes to keeping weight off. It also validates the suggestion that eating less — not exercising more — is the key to dropping those excess pounds.
What’s different about this study, however, is that the data on energy intake and energy expenditure didn’t rely on selfreporting.
Controlling for diet and exercise is expensive and timeconsuming, which is why most studies rely on data garnered from diaries or recall submitted by the study subjects themselves. And because most people overreport how much they exercise and under-report how many calories they consume, it’s been tough to get a realistic handle on the impact of both weight-loss strategies.
But it’s not just losing the weight that’s important. Obesity is considered a chronic condition, which means any “cure” needs to last longer than a few months — even a few years. So the goal isn’t just taking the weight off, it’s keeping it off, which is where exercise has the most impact.
It’s also clear that the simple calories in/calories out equation that used to guide weight loss is losing favour. Instead, a far more nuanced approach is emerging. Still, the two big players — eating less and exercising more — remain in the mix. The question about how to best manipulate both to achieve the desired results, however, remains unanswered.