Two new studies in the August issue of Obesity help shed light on the phenomenon whereby a person's metabolism slows down in response to a large drop in weight — so-called "metabolic adaptation." This makes it difficult to maintain a weight loss larger than about 12% of initial body weight.
One of the studies describes the ups and downs of weight loss as documented in the US televised competition The Biggest Loser, detailing the process by which participants lost massive amounts of weight with an intense, supported diet and exercise program over 30 weeks. But almost all of them had regained nearly all of their lost weight a few years later, indicating that maintenance of massive weight loss is largely unsustainable in everyday life.
The main reason for this is that the large weight loss triggers a "resetting" of the resting metabolic rate to very low, a process that is outlined in the second paper.
"The lesson from both studies…is that weight loss triggers a well-documented change in energy expenditure that occurs to counteract the change in weight… a 'thriftiness,' " note Eric Ravussin, MD, and Donna H Ryan, MD, from Pennington Biomedical Research Center, in Baton Rouge, Louisiana, in an accompanying editorial published online July 27.
And importantly, "the lowered energy expenditure is disproportionate to the magnitude of the weight loss," the editorialists explain.
This means that for most people, "weight-loss maintenance is difficult," and so "individuals affected by overweight or obesity and struggling to control their body weight can finally be excused for not trying hard enough. Society and health professionals, too, can stop blaming the victims," they add.
The main take-home message here "is that modest weight loss can produce major health benefits, even in individuals with extreme obesity," Drs Ravussin and Ryan stress, noting that the focus should now shift away from striving for dramatic amounts of weight loss toward achieving moderate weight loss with a stronger emphasis on weight-loss maintenance.The Biggest Loser
In the first study, Erin Fothergill, formerly at the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), in Bethesda, Maryland, and colleagues examined metabolic adaptation in 14 participants in The Biggest Loser, 6 years after the competition ended.
On average, the 14 participants weighed 149 kg at the start, lost 58 kg at the end of the 30-week contest, but weighed 137 kg 6 years later.
And even though the participants regained, on average, 80% of their lost weight, perhaps surprisingly, their resting metabolic rate stayed at the same suppressed level as it had been at the end of the competition (when they were at their lowest weight).
In addition, those with a greater long-term weight loss had a greater slowing down of their metabolism.
"Therefore, long-term weight loss requires vigilant combat against persistent metabolic adaptation that acts to proportionally counter ongoing efforts to reduce body weight," Mr Fothergill and colleagues caution.
The research made front-page news in the New York Times in May and sparked a slew of accounts online about struggles with weight regain after large weight loss.Models to Explain Metabolic Adaptation to Weight Loss
In the second study, Michael Rosenbaum, MD, and Rudolph L Leibel, MD, from Columbia University, New York, detail potential models of metabolic adaption in response to weight loss using data from 17 obese subjects before and after they lost 10% and 20% of their weight.
They conclude that metabolic adaptation is a combination of a "mechanical" model (energy expenditure depends on the body's weight "set point"), a "threshold" model (metabolism is slowed when fat stores fall below a certain threshold), and a "spring-loading" model (the more weight that is lost, the more the "spring" stretches out, and the harder it will be to snap back).Lessons Learned: Maintaining Weight Loss Is What's Important
According to Drs Ravussin and Ryan, writing in the editorial, the lessons learned from these two studies are:
The dramatic weight loss seen on The Biggest Loser requires a team of support people, and such a heavy-duty regimen is difficult to maintain in the real world.
A weight loss of 5% to 15% is sustainable and has known health benefits.
Physiological responses to weight loss likely drive weight regain.
Metabolic adaptation to weight loss is less with moderate weight loss.
With a 5% to 15% weight loss, patients might see only a small deficit in resting metabolic rate (50 to 150 kcal/day).
When clinicians counsel obese patients about making changes in diet and physical activity to lose weight, they should also include plans for how patients will handle weight regain.
To keep lost weight off, patients need to stick with the lifestyle changes they made to lose weight; continue to take medications, if indicated; get enough sleep; avoid stress; avoid medications that cause weight gain; and weigh themselves often so they can act quickly to use the same strategies that they used before to lose any small weight regain.
Bariatric surgery may be an option for certain patients, but even with this surgery, patients may regain weight.
Thus, an emerging frontier in obesity research is "weight-loss maintenance," according to Drs Ravussin and Ryan.
"We need to better understand the biology behind weight regain if we are to improve treatment," they observe.
Until then, "we need to be more accepting of variation in body size and focus our efforts on improving the health of our patients who are affected by comorbidity related to excess body fat," they conclude.
The authors have declared they have no relevant financial relationships. Drs Ravussin and Ryan are the editors of Obesity.
Medscape Medical News © 2016
Cite this: The Biggest Loser: Weight-Loss Maintenance Should Be Focus - Medscape - Aug 08, 2016.