It would be great if an acclaimed — and more importantly, extremely widely read — U.S. newspaper could boast “Health” and “Science” sections that boasted consistently impressive articles. This one is getting a lot of attention, and with good reason: something like two-thirds of adult Americans are considered overweight, millions of them are trying to shed pounds, and Gina Kolata’s article in effect conveys the message that they are screwed.
I’m going to assume that anyone reading this has read the article and the study it draws from or at least has tabs open to these, because I am not going to review it in depth.
A couple of very quick, seemingly obvious, and (perhaps deliberately) underemphasized or omitted points:
- The study sample is extremely small (n = 14).
- The study sample is, by definition, not even close to a representative sample of the population. It’s not even representative of “typical” overweight or even obese people. My understanding is that participants on The Biggest Loser are people who are not only extremely obese to start with but have struggled with morbid obesity for a long time, possibly their whole lives.
These two points together imply that any data extracted from the study results, however meticulously collected and analyzed, cannot be reliably generalized to the U.S. population at large.
If we looked at a dozen or so former NBA players, and looked at their average vertical leap at age 30 and again at age 50, we would not expect to see numbers at either end reflecting typical absolute values (they would clearly both be far higher than the population average) and we would not expect the average decline in jumping ability to mimic the typical American’s decline (presumably, they would lose far more inches because of greater deconditioning — the average person is a couch potato or moderate exerciser at best from early adulthood into early middle age).
So it’s probably safe to assume that the persistent in lowering RMR (resting metabolic rate) that The Biggest Loser participants experienced from the time they appeared on the show until six years had elapsed after their participation ended is atypical.
This is owed not merely to the unique physiological characteristics of the participants at baseline, but to the extremely unusual way in which they went about losing weight during their months on the show. They exercised to an insane degree, with an intensity that very few human beings accomplish alone, and also that very few human beings could reasonably be expected to maintain once the incentive of living in a controlled environment — under the scrutiny of not only a team of dieticians and physical trainers but millions of television viewers — was removed.
But that’s not even the most important thing Kolata failed to explore.
The article notes that the average study member’s RMR, after dropping about 600 calories a day during the period in which they lost weight (an average of 58 kg, or 128 pounds)on the show, has continued to decline by an average of about 100 calories a day even as they have regained an average of 41 kg, or 90 pounds. That, no question about it, sucks. It makes it seem as if regaining weight after losing it owing to a very dedicated exercise and dieting regimen is virtually inevitable. But it doesn’t suggest that the continued slowing of RMR was entirely causative in terms of weight gain. There’s no real way to know from these results what the RMR of this group would have looked like had they found a way, as superhuman an effort as it might have required, to keep the lost pounds off.
Moreover, the article also says that in the six years since Season 8 of the show ended, one contestant, Danny Cahill, has regained about 100 of the 239 pounds he initially lost from his 430-pounds frame “despite his best efforts.” But it doesn’t say exactly what those efforts have included. The show’s medical doctor acknowledges that “many contestants are unable to find or afford adequate ongoing support with exercise doctors, psychologists, sleep specialists, and trainers.” In other words, they probably aren’t working nearly as hard, or even close to as hard. And really, how could they? All they did with their lives for months on end was try to lose weight. They probably thought about little else. And after they were no longer contestants on the show, they all returned to their everyday lives — jobs, kids to take care of, and no one watching them. They went from being de facto lab rats to people again.
On top of that, they were even hungrier, and in the face of metabolisms that for some reason were especially unforgiving. Big decreases in serum levels of the oft-cited hormone leptin, which promotes satiety, seems to be largely responsible. Whatever the case, most of the former contestants interviewed admitted that they frequently gave into these cravings, as real people who are hungry do, and ate more than they wanted to.
Anyway, the apparent take-home message — that if you work your ass off to lose weight, it’s probably in vain because you’ll only put the brakes on your own metabolism — is not only depressing, but largely unfounded, at least based on this one study.
A small number of extremely overweight people with already disadvantageous metabolisms lost a ton of weight using otherworldly dietary and exercise regimens and then, over six years, gained a lot of it back while not exercising nearly as much and keeping to the same nutritional habits.
This doesn’t mean that if you are, say, 50 or even 100 pounds heavier than you “should” be, and you start exercising faithfully but within sane and maintainable limits, you’re doomed to get fat again unless you keep ramping up how much you exercise and ramping it up even more, all while continuing to starve yourself because of a putative ongoing decline in RMR. That’s not what the study, which most likely doesn’t really apply to you anyway, demonstrates in the first place.
There is, in a sense, an extant “control group” in the mix here — people who started out very overweight, started exercising, and maintained their lower weight over time. You see them at road races and elsewhere, and they are not biological freaks. Obviously it is easier for some people to do this than others, but looking only at the people who by definition had the hardest time of all to begin with and were unable to stick with the program that got them to lower weights doesn’t really tell you anything useful.