Weight Loss and Decreased Metabolic Rate: It’s Not as Bad as You Think
I believe it is not uncommon to pay a sit-down visit to the bathroom in order to become as light as possible before stepping on the scale. On a related note, do you remember when many people lost their shit over that 2016 New York Times article about how significant weight loss crashed the metabolisms of contestants on that fat-shaming train wreck of a game show The Biggest Loser?
It’s an interesting piece that reveals tremendous disparity in resting metabolic rate (RMR) between those who has lost a lot of weight compared against weight matched controls (people of the same weight who had not lost weight).
On social media I saw many who desire to lose weight get discouraged by the piece, and while I’ll never say that weight loss is easy, the research shown in the article makes it appear hopeless. But it’s far from hopeless, especially once we start actually dissecting the body of research in this area and providing context for the RMR disparity.
First off, which the article was most clear about, is the fact that these people under study went through the most ridiculous methods imaginable for losing weight. I railed against this travesty of a program in a feature piece for the Guardian just before the 17th season premiere and showed that, yes, that kind of extremely rapid weight loss does indeed aggressively dial down resting metabolic rate. Fortunately, the 17th season ended up being its final one.
In the NYT piece we learn that even though it’s been years since the show, former contestants Danny Cahill “burns 800 fewer calories a day than would be expected for a man his size,” Dina Mercado burns 437.9 fewer calories per day,” Sean Algaier “burns 458 fewer calories a day,” Amanda Arlauskas “burns 591.1 fewer calories per day,” Rudy Pauls “burns 516 fewer calories a day,” and Tracey Yukich now “burns 211.7 fewer calories per day than would be expected for a woman her size.”
Yikes. It is enough to make anyone think sustaining weight loss is hopeless. Except when put into context. First off is a potential genetic confounding variable.
“The people on The Biggest Loser probably have a strong genetic tendency towards obesity, because the average BMI at the beginning for these contest is at around 50.” This said to me by Dr. Karl Nadolosky, an endocrinologist in Bethesda, Maryland. The fact that they were at such a significant body weight to begin with implies a strong possibility that their metabolic rate may have been slow for any number of reasons, which contributed to them achieving such high obesity in the first place. “There is a lot of individual variance with these things,” he said.
Now let’s couple this with not just the extreme amount of weight loss they underwent, but the very high rate at which they lost it.
In my piece for the Guardian, former contestant Kai Hibbard told me she was consuming fewer than a thousand calories a day while exercising around eight hours per day. The sheer size of the caloric deficits the contestants on the show achieve are orders of magnitude larger than what is considered “rapid” weight loss in the medical community.
And the biggest thing to take note of is that the contestants were not exactly weight stable during the measurements. I spoke with obesity researcher James Krieger of Seattle, who dissected the study to learn more.
“The best work in this area is by Rudolph Leibel,” Krieger said, referring to a 2008 study published in the American Journal of Clinical Nutrition. Krieger explained the study took people who had lost 10% of their body weight or more and ensured they were truly weight stable by keeping them confined in a metabolic ward and hyper measuring not just caloric intake and expenditure, but carbohydrate and sodium intake (which can affect the body’s water balance). “Their weights were so stable they had less than a 20-gram variance from day to day,” said Krieger.
Why is this important? Because weight fluctuations have an almost immediate effect on RMR. And guess what? The former biggest loser contestants were not weight stable. On average, they were losing about half a pound a week. Not a lot, but enough to very likely affect the results. Krieger also explained that it appears as though these contestants had ramped up their physical activity as well, which would further have a decreasing effect on RMR.
“It’s like when you finally start flossing a week out from the dentist,” Krieger explained. He can’t be certain, but logically it makes sense that, knowing this testing was going to take place, and that all of these contestants had regained some or even all the weight, that they might engage in the weight loss version of last minute flossing. This hypothesis is supported by the higher than expected total daily energy expenditures of the contestants compared to what most research indicates regarding people who have lost considerable weight.
All these potentially confounding variables puts the dramatic differences in RMRs between former TBL contestants and weight matched controls into better context. Yes, it is true that losing weight lowers metabolism. It is also true that if you take two identical twins, and one gains a lot of weight for several years, then loses all that weight to get back down to the same weight as the “never fat” twin that the one who had been fat is going to have a lower RMR than the one never gained weight, and this imbalance between twins will likely persist for many years and possibly for life.
And this article doesn’t even get into the other things like the way the brain can be rewired to crave highly palatable food, adaptations in hunger hormones, and the difficulty of breaking habits that contributed to gaining fat in the first place.
Back to RMR: How big is the imbalance? The answer is: we don’t know for sure. According to the research cited in the TBL article it seems like the imbalance can be huge, but remember all those confounding variables that contribute to it. Chances are very few will apply to you in your efforts to lose weight, and the degree of any RMR imbalance that you may experience compared to weight matched controls will likely be of a manageable size.
That is, it you don’t adopt the dumbass Biggest Loser method of weight loss. The aforementioned study by Leibel where a metabolic ward was used to ensure participants were weight stable saw that the persistent lowering of RMR was only about 5-8% less than that of weight-matched controls. Those are percentages that can be worked around.
Tortoise Vs. Hare
For my piece in the Guardian I spoke with Eric Ravussin, a professor of human physiology at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, who told me, “On The Biggest Loser the lowering of resting metabolic rate is much more significant than you would expect.”
In 2012, Ravussin helped design a study involving contestants from The Biggest Loser that was published in the Journal of Clinical Endocrinology & Metabolism. “I went to their place (the show’s weight loss ranch) and had a post doc of mine who went three more times,” Ravussin told me. “We shipped a metabolic cart to measure their metabolic rate and body composition.”
Ravussin and his team compared 12 people from The Biggest Loser and matched them with 12 people who had lost similar amounts of weight via gastric bypass surgery. The surgery group lost a lot more not fat than the biggest loser group. Both groups lost “fat free mass” (FFM), which includes losing muscle, but for those who underwent surgery 30% of their weight loss was FFM and for contestants of The Biggest Loser the weight loss from FFM was only 16%.
This is easily explained by the fact that those on the TV show were exercising like God threatened to shove a lightning bolt somewhere sensitive if they didn’t stay on that treadmill. And even though the insane exercise regimen meant TBL contestants lost less muscle and more fat (muscle is more metabolically “active”), their drop in resting metabolic rate was double that of the gastric bypass group.
In other words, despite all the exercise, the metabolisms of the biggest losers crashed hard. Way harder than those who lose weight at a more rational pace. A follow up study published in 2014 in Obesity found that the disparity in RMR between those who had gastric bypass and TBL contestants persisted.
We’re kind of comparing apples to oranges. Gastric bypass is known to have some RMR sparing effects that we only partially understand, which is one of the reasons why it’s one of the most effective long-term methods of weight loss, with about a 75% success rate, according to obesity researcher Dr. Arya Sharma. In terms of how gastric bypass spares RMR, Dr. Nadolsky went full endocrinology geek on me: “It has to do with very complex neuro-endocrine pathology and patho-physiology of obesity from the central neuro-endocrine stuff to the peripheral gut hormones and the leptin.” So, uh, yeah. There you go.
But what happens when you compare apples to apples? Slow weight loss via lifestyle change compared to rapid?
For one thing, people who lose weight fast have a greater loss in fat-free mass (FFM – stuff you don’t want to lose, like muscle) than those who lose weight at a more moderate pace. Dr. Nadolsky explained that he recommends his patients engage in resistance training to prevent such a loss of FFM, mostly for metabolic health, but also because it can make a difference in terms of preventing weight regain.
You’ve likely heard that adding muscles amps up RMR, but I pointed out years ago in the LA Times that those numbers are vastly overblown. Nevertheless, preventing loss of FFM is still a great idea.
There is also the fact that, as both Dr. Nadolsky and James Krieger told me, the size of the caloric deficit does have an effect on RMR during the weight loss stage, but we can’t be certain if a higher rate of weight loss results in a more drastic extended drop in RMR compared to those who lost weight more slowly. I mean, we can guess that it might, but the research isn’t there yet to be definitive.
My friend Dr. Yoni Freedhoff, an obesity physician in Ottawa, Canada, recommends a maximum rate of weight loss of 1 lb per 100 lbs of body weight per week. So, if you weigh 200 lbs, you can lose at most 2 lbs per week, but if you’re 300 lbs you can lose at a rate of 3 lbs per week, adjusting this rate downward as weight is lost. Although he says there are many reasons for not exceeding this rate, such as what has been discussed in this article thus far, his most important reason is that any faster than that is unsustainable.
Because, generally speaking, the lifestyle you adopt to lose weight is the one you have to sustain to keep it off. I wrote an article a while back that breaks down the numbers for hitting this maximal recommended rate of fat loss, and even though it’s nowhere near what happens on TV, it still involves pretty aggressive lifestyle change.
One thing Dr. Nadolsky mentioned is that research shows that people who lose weight faster have a tendency to keep it off, but it’s important to define what “faster” means. A well known study of 5,145 people published in Obesity in 2011 did a four-year follow up of people who had undergone substantial weight loss and determined that those who lost weight the fastest were the most likely to keep it off. But it’s important to point out that this “fast” rate of weight loss was still less than a pound a week.
There are a few important things to realize in all of this.
The first is that, because they were not in a metabolic ward, the study of The Biggest Loser contestants was not well controlled, making it subject to some confounding variables, and is WAY outside what the almost everyone who loses weight will ever experience.
Second is that, while losing weight may make a person have a lower RMR than a weight matched control who was never fat, it’s probably not going to be that significant of a difference to dramatically increase the challenge of keeping the weight off, especially if you lost the weight at a sustainable pace.
Third is realizing that RMR is only one part of the equation. Total daily energy expenditure (TDEE) is what really matters. How many calories are you burning in a day? If your weight loss journey involves getting more active and you keep it up, then you can have a very reasonable TDEE which allows for eating a rational amount of healthy food to maintain your weight loss while not feeling like you’re starving. And while metabolic rate may decrease, endurance for all types of activity can increase via sustained effort, which can also positively affect TDEE if you keep putting that higher endurance to good use.
Perhaps most important of all is your attitude. While a lot of TBL contestants regain the weight, some keep it off because of the tremendous pressure of having lost it so publicly. For those who did not lose weight on a game show, they can go through a major mental shift that compels them to lose weight and keep it off.
These stories exist. Losing weight is not easy and requires thoughtful and persistent dedication to steady changes that allows you to lose weight and keep it off. Yes, there are things your body will do to fight losing weight, but knowledge is power.
And with that knowledge, you can fight back.
James S. Fell, MBA, writes for the Los Angeles Times, Chicago Tribune, Women’s Health, Men’s Health, AskMen, the Guardian, TIME Magazine and many other fine publications. His first book was published by Random House Canada in 2014. He is currently working on his next book, which is about life-changing moments.