Researchers (note, emphasis mine):
studied the impact 7 months of Biggest Loser weight loss had on the resting and total energy expenditures of 16 participants. They used all the latest gadgets to do so including indirect calorimetry and doubly labeled water. So what happened? By week 6 participants had lost 13% of their body weight and by week 30, 39%. More importantly by week 6 participants metabolisms had slowed by 244 more calories per day than would have been expected simply as a function of their weight loss and by week 30, by 504 more.
Wow. Drilling down into the study we learn that this is despite the fact that lean body mass was in fact largely preserved. Yowza. As Yoni says, this is not how you want to start approaching weight maintenance!
Yoni then compared TBL study results to a study of bariatric patients who had similar weight loss, but whose metabolisms did not slow down more than would be expected by weight loss. Yoni’s take:
Metabolically speaking, it would seem to me that [Biggest Loser’s TV doctor Dr. Robert Huizenga’s] own study would suggest bariatric surgical weight loss is far healthier to a body’s metabolism than is Biggest Loser style loss.
Well, I’ll grant that in terms of energy expenditure that may be true, but please, don’t go running to your docs for weight loss surgery! It’s not at all clear what the implications are 5 or 10 years down the road, especially for irreversible WLS. Metabolism may be restored, but if you’re missing part of your digestive system, it’s very likely that difficulties with absorption of essential nutrients may be far less healthy longer-term.
Also of interest, Yoni did note that the two studies tested participants at different lengths of time from the start of weight loss and acknowledged that “perhaps the Losers’ metabolisms will improve with time.”
This is an interesting question that Evelyn/CarbSane tackled on her blog last year. She looked at the fat metabolism of formerly obese women (part 1, part 2, and part 3) and noted something similar. It may be that the most difficult part is the first year after weight loss, and that as Evelyn notes in a comment:
The [National Weight Control Registry] data seems to show that “recovery” of the metabolism — whether it was caused by the obese state or prolonged energy deficit — is possible.
Now, that said, this is in no way meant to suggest that I endorse Biggest Loser-style weight loss because it’s possible that these metabolic deficits can be corrected. I went thru a period in the mid-90s that I characterize as my “exercise bulemia” period. I think I have the records I kept somewhere, but my recollection is that I averaged something like 1200-1500 physical activity calories a day (which might be something like 9 miles of walking, plus rowing in the AM, followed by working out on the bike or Stairmaster).
As Yoni points out, TBL participants who are so inclined (i.e., those with new livelihoods as trainers or product spokespeople) can keep up the regimen necessary to maintain in the face of a whacked metabolism (I did it a year and a half until my mother died), but for most — including TBL contestants like Eric Chopin — the post weight loss honeymoon from this approach is a short one at best.
Me, I’ll probably still watch TBL (guilty pleasure or train wreck, can’t decide). But IRL (in real life ;), for me now it’s all about realistic lifestyle changes for the long term.