Don’t Give Up on Weight Loss Because of "Biggest Loser"
Tufts research doesnít support surprising findings of slowed metabolism.
If you followed the headlines about a recent study of contestants in the "Biggest Loser" reality-TV show, you might be despairing about your own chances of maintaining a healthy weight. The study, published in the journal Obesity, tracked contestants appearing on the show’s eighth season, with 14 of the 16 willing to be re-measured six years later. On average, participants gained back more than two-thirds of the pounds they lost on the program’s extreme diet and exercise regimen; some are even heavier now than before.
Why? Researchers led by Kevin D. Hall, PhD, of the National Institutes of Health, reported that contestants experienced a drop in their metabolic rate that Hall described as "shocking and amazing." Before their TV experience, the contestants were all extremely obese but had normal resting metabolisms: When at rest, they were burning the number of calories to be expected at their weight. But after their dramatic weight loss, their metabolisms had slowed so their bodies were not using enough calories to maintain their slimmer size. And over the next few years, as contestants regained weight, their metabolisms became even slower.
Does this mean long-term weight loss is simply hopeless? Susan B. Roberts, PhD, director of Tufts' HNRCA Energy Metabolism Laboratory and author of The “I” Diet <www.theidiet.com>, says not so fast: "We should be careful about drawing conclusions from a single study of 14 individuals, no matter how dramatic the results may be.
"The coverage of this story is important because it shows us just how harmful it can be to lose massive amounts of weight unnaturally quickly with extreme regimens. (Seven hours of exercise a day, anyone?) But the study does not cover, and therefore says nothing about, how metabolism responds to reasonable weight loss that is achieved by reasonable means."
TUFTS FINDINGS: In contrast to this tiny study, Roberts' Energy Metabolism Lab has published two more expansive studies that show almost no negative effect of weight loss on metabolism, beyond what would be expected from weight loss alone. In one, 145 participants lost 11% of their body weight and kept it off for the two-year duration of the study. Participants experienced a drop in metabolic rate of just 5%, and a reduction in total calorie requirements of only 7%.
Tufts scientists also studied the relationship between reducing daily caloric intake and metabolic rate among 30 patients undergoing gastric bypass. Their average weight loss of 38% was associated with a decrease in their metabolic rate of 26%, while their total calorie requirements contracted only 24%.
"These studies show a healthy parallel decrease in weight, metabolism and calorie requirements, or even a smaller decrease in metabolism than in weight," says Roberts. "They do not show unnatural or harmful drops in metabolism."
REALITY CHECK: The concept of extreme metabolic adaptation to weight loss has been blown out of proportion by media coverage, Roberts adds. "But even this 'Biggest Loser' study doesn’t really support this idea, because the study used different machines to measure metabolic rate at different times - which can make a big difference." Participants' total calorie requirements, measured by a different method after six years, were decreased by just 10% when their weight was 12% lower than before the program. "Again, that suggests no measurable decrease in total calorie needs beyond those due to becoming smaller," Robert says.
By contrast, she notes, several scientifically rigorous studies conducted on people losing weight by less extreme methods indicate that calorie requirements do seem to decrease with weight loss, but the decrease is approximately in proportion to pounds lost. "This is a much different and more positive message. Rather than instilling the sense of futility that characterizes the experiences of the TV contestants, this shows that healthy weight loss can lead to healthy prevention of weight regain when we continue the effective habits that made weight loss possible in the first place. Plus when resting metabolic rate decreases in proportion to weight loss it means that metabolism remains normal, not unhealthily low.
"It is not appropriate for the media to extrapolate broad conclusions from a small self-selected group of people undergoing bizarre and unsustainable regimens that are entertaining as in a reality show but are not sustainable," Roberts says. "My recommendation is to recognize the dramatic weight loss experienced on the TV show is an aberration that should not be confused with the experiences of those who embark on a moderate, healthy, well-designed regimen to lose weight and to keep it off."
ADJUSTING CALORIES: Since calorie requirements do decrease once your body is smaller, preventing weight regain requires permanent changes to calorie intake. It also requires reasonable amounts of exercise - but not what the "Biggest Loser" contestants endured. Consuming 10% or 20% fewer calories isn’t something that happens automatically, but it doesn’t need to be a life sentence of deprivation, because in fact calorie needs do not drop below those of a normal-weight person after weight loss finishes. Many of the good new habits learned during reasonable weight loss can be maintained to prevent weight regain.
Roberts concludes, "'The Biggest Loser' is certainly entertaining, but the most important lesson we can draw from this study is: Don’t try to lose weight 'The Biggest Loser' way!"
TO LEARN MORE: Obesity, online May 2, 2016 -†