Resting Metabolic Rate (RMR)
& Healthy Weight Loss
A recent study of Biggest Loser participants claimed that the slowdown in metabolic rate was to blame for weight regain – what’s the truth?
According to the study, successful weight loss sets up a catch-22 where a slower metabolism and increased hunger make maintaining weight loss almost impossible.
“The more successful you are at losing weight, the slower your metabolism will be and the more hungry you’ll be.”
Senior Investigator, National Institutes of Health, NIH.gov
What does this catch-22 really mean? If you’re overweight, do you have to choose between staying overweight or torturing yourself with an unending cycle of losing weight, only to be tormented by hunger until you regain it? Does losing weight damage your metabolism? Or is there a better way? Can you truly lose weight and keep it off without hunger? The health experts at Pritikin answer these questions and cut through the hype with evidence-based facts.
What is Resting Metabolic Rate (RMR)?
Amidst the optimism that the TV show has spread for years by transforming lives through weight loss, the study of Biggest Loser participants revealed what many could have already guessed: The majority of them were unable to keep off most of the weight they lost on the show. This is certainly the case for most people who have ever embarked on a journey to shed unwanted weight. When a person loses weight, the decline in his or her resting metabolic rate (RMR) is “often greater than would be expected based on the measured changes in body composition,” according to the study’s authors. This decline in RMR that follows a drop in body weight is what they refer to as metabolic adaptation. Working to counter weight loss, it is this metabolic adaptation that the study leaders thought to be one of the biggest culprits promoting weight regain.
However, as Pritikin’s Director of Nutrition and educator Kimberly Gomer, pointed out, the results of this study are quite extreme and an outlier compared to all other previous research on the topic. True, research has proven over and over that crash diets don’t work. But the reason for regaining weight may have more to do with what foods and drinks people consume after losing weight than with a much slower metabolic rate.
“We know biologically the main reason people tend to regain weight after following a calorie-restricted diet coupled with increased activity has less to do with some metabolic adaptation and more to do with the fact that people are smaller, and smaller people simply need less food to maintain their smaller body size,” he explained. More importantly, “the main reason people regain weight after a crash diet and exercise program is that they are very hungry, and this increased hunger is what drives them to eat more and regain weight. Chronically hungry people may also be more lethargic and thus, end up moving less.”
That’s why at the Pritikin Longevity Center in Miami, there is no crash diet or extreme exercise program put into place. From day one, guests learn that counting calories and using intellectual will to fight increased hunger is not the answer. Instead of counting or restricting calories, the focus is on what foods promote obesity and what foods promote a healthier body weight. Natural, whole foods that have a low calorie density are one key strategy for not only losing excess weight without being hungrier, but also keeping it off in the long run. Through nutrition education and wellness classes, they understand that the Pritikin Eating Plan, accompanied with a customized fitness regimen, can help guide them to optimal weight and health.
The Study Results
The study, “Persistent metabolic adaptation 6 years after ‘The Biggest Loser’ competition,” measured changes in both body composition and resting metabolic rate over time for 14 game show participants. With the hypothesis that metabolic adaptation tends to continue several years after weight loss, researchers chose to follow six male and eight female participants for six years. These individuals had lost an average of 128 pounds by the end of that season’s show, yet just six years later they regained an average of 90 pounds, reported Runner’s World magazine in a follow-up article to the study. That totals a net weight loss of just 38 pounds, or an 11.9% average weight loss for all 14 study participants after six years.
To maintain weight loss, individuals must consume a significantly lower number of calories per day due to the fact that RMR accounts for close to 70% of calorie burn, reported Runner’s World. While the quite unusual circumstances of the 30-week competitive weight-loss show may have helped significantly with weight loss initially, such reduced caloric intake becomes very difficult to maintain.
“Americans have been going on calorie-restricted diet and exercise programs for decades and we keep getting fatter. The latest data show that 40% of American women are obese and 35% of the men are, too. Most of them have tried diet and exercise plans and lost weight, only to regain it.”
Nutritional Research Specialist and Educator
To break it down with numbers, those competing on “The Biggest Loser” were initially burning 3,804 calories per day at the time when they were most sedentary and weighed 328 pounds, on average. Their RMR was close to the predicted amount based on a standard formula. After 30 weeks on the crash weight-loss program, the subjects were burning 3,002 calories each day, despite doing an hour of exercise daily.
There is no doubt, according to Gomer, that the reduction in calories burned was due in large part to being smaller – since they had lost an average of 128 pounds over the 30 weeks. This is where the double whammy comes in: At week 30, participants’ RMRs declined by an average of 611 calories per day. On average, they were burning 275 calories less than what was predicted based on the weight they had lost. Thus, almost half of their slower RMRs were due to metabolic adaptation.
However, the study found that the ensuing weight regain was not “significantly correlated” with the degree of metabolic adaptation even though participants from the study who had lost the most weight at the completion of “The Biggest Loser” actually showed the most significant slowing of RMR at that time. Moreover, contestants who kept the most weight off after six years also encountered greater ongoing metabolic slowing. The researchers concluded that “metabolic adaptation is a proportional, but incomplete, response to contemporaneous efforts to reduce body weight from its defended baseline or ‘set point’ value.”
The anomalous finding, according to Gomer, was that this slowdown in metabolic rate actually increased over the next six years despite the fact that most of the 14 subjects regained all, or most of, the weight they had lost. Their results showed the metabolic adaption increased from 275 kcal after the weight was lost – following the 30-week crash diet – to a whopping 499 kcal six years later, despite most of the lost weight being regained.
This finding of increasing metabolic adaptation, despite weight regain, is incongruous with prior research that has suggested RMR tends to return to normal when lost weight is regained. This metabolic adaptation is also referred to as the “metabolic penalty” or “fat memory” that postulates that the RMR drops and stays lower as long as the weight is kept off. This metabolic penalty coupled with increased hunger certainly helps explain why most people have trouble sticking to a calorie-restricted diet and keeping off lost weight over the long-term.
Can You Lose Weight Without Damaging Your Metabolism?
In a follow-up article to this study, The Washington Post – along with many other media outlets – questioned what this phenomenon really meant for everyone else, asking if there were a metabolic penalty for getting lighter. As Gomer explained, though there is a modest slowdown in metabolic rate following weight loss, the so-called “metabolic penalty” is not the main reason most people end up regaining lost weight. As many have pointed out since the surfacing of the Biggest Loser study, the circumstance of these participants was quite abnormal.
Furthermore, as Gomer mentioned above, people tend to gain back the weight they lost largely because they are much hungrier and tend to eat more. Instead of being consumed with counting calories, the focus should be on food – food choices that fill us up. We need foods that are big and filling, but are not big in calorie density. Natural, whole foods with a low to moderate calorie density are the cornerstone of the Pritikin Eating Plan. These healthier food choices help people feel satiated on far fewer calories. This then allows people to lose weight and keep it off without being hungrier than normal despite losing a lot of excess weight.