Earlier this week, a study was published online in the journal Obesity that caused quite a stir. The study, titled "Persistent metabolic adaptations 6 years after 'The Biggest Loser' competition," sought to determine whether the contestants of this outrageously popular show experienced long-term changes to their resting metabolic rate and, as a result, their body composition.
The results themselves were pretty clear. Most contestants from the show regain weight despite their best efforts to maintain their new physiques. The more informative conclusion, however, is that the contestants studied experienced persistent declines in their resting metabolic rates; that is, their bodies continued to slow down. People seem to comprehend this part. We collectively seemed to trip up over the part about "battling biology."
First, some basic physiology: the bigger you are, the higher your resting metabolic rate. So, if you lose weight, your metabolism often slows down with it. That is because it takes less energy to move and maintain 150-pound body than to move a 225-pound body. There is just less "body" to deal with. However, in a healthy body, once weight loss stops, so should the rate of decrease in resting metabolic rate. In fact, if the person eats right and exercises appropriately, it can recover back to a higher rate.
This expectation was not observed with the contestants of The Biggest Loser. Contestants from this show never recover their resting metabolic rate. Even worse, many of them continued to burn fewer and fewer calories per day. One former candidate burns 552 fewer calories a day than what would be expected of somebody her size; another's measured resting metabolic rate is over 800 calories below the calculated baseline. With a metabolism that is perpetually slowing down, it's easy to understand why some of them can't help but to gain weight back.
Now, the authors of this study used this observation to explain that weight loss is a battle with the body's biology. This tragically-phrased statement has been misinterpreted and misrepresented across popular media and all over the internet. I have seen assertions that certain people are biologically destined to be fat. One interpreted this study to say that weight loss efforts are pointless.
As somebody with a scientific background, and as someone with metabolic issues of my own, this is infuriating. This study does not say that your body is destined to gain weight, nor does it say that efforts to lose weight are in vain. In fact, in an article in The New York Times, one of the authors of the study explicitly said that this "shouldn't be interpreted to mean that we are doomed to battle our biology or remain fat."
What the study did say, and what every successful weight loss story on the planet can attest to, is that extreme methods will only backfire. Rather than working against biology, we need to examine biologically sound approaches to dealing with our world's obesity problem.
The battle against biology isn't weight loss itself; the battle is that much of our conventional weight-loss wisdom works against our physiology. When somebody starts The Biggest Loser weighing nearly 400 pounds, and then has their diet restricted to 1,000 calories a day while working out for hours and hours, their body will think it is starving because, well, it IS starving. Most people understand that, even though it contradicts the "calories in < calories out" approach. But a more average person may unintentionally confuse their body into thinking they are going hungry. Guess what your body doesn't want to do when it thinks it's starving? Use precious energy (i.e. burn calories).
Let's use a sample case: a 27-year-old woman who is 5'5" and weighs 180 pounds has a resting metabolic rate of approximately 1,700 kilocalories/day. (This is just an example; actual RMR varies from person to person.) This means that if she just rests comfortably and does nothing — not even eat — she will use approximately 1,700 calories just being alive. Add in digestion, a semi-active job, and an hour of moderate-to-intense exercise, and this woman's total daily energy expenditure could easily exceed 2,500 calories. If she follows the common weight-loss advice of consuming 1,200 calories, she is putting herself into a calorie deficit of over 1000 calories per day.
When a person is in that deep of a calorie deficit for very long, the body will slow down to conserve energy — because why would you be eating so little if there weren't a food shortage? (This is how our predecessors used to survive periods with less food, back when there wasn't a Kroger just around the corner selling 130 different varieties of cheese.) When the body slows down to conserve energy, muscles will atrophy, sex hormone levels will plummet, and the thyroid can simply decide to hibernate for a while.
Athletes, especially bodybuilders, figured this out decades ago. In order to burn calories and have energy, you have to keep your body happily humming along like there isn't any distress in the world for it to worry about. Athletes did not get their powerful muscles and toned looks by eating 1000 fewer calories than they burn every day. They got there by fueling their activities with the energy their bodies need. Somehow, I doubt that Abby Wambach and Michael Phelps go to bed hungry. And yet they aren't fat! Their metabolisms work in their favor because they take care of themselves. This is the exact opposite of what the contestants on The Biggest Loser experienced during their weight loss journey, and that is why their metabolisms have struggled to recover from such an extended and extreme period of starvation.
I am not an athlete, but I am a person that wants to be healthier. That process is, of course, complicated by my bum thyroid. Once I started medication for it a few months ago, I was anxious to figure out exactly how much I needed to be eating to improve my health. While there are many worthwhile programs out there, I began using one called Eat to Perform, designed so people can get the energy they need to exercise and improve their body compositions. Based on a variety of factors, the program determines how much protein, fat, and carbohydrate nutrients you need to eat in a day.
When I got my numbers (my "macros"), I was a little nervous. I was supposed to eat almost 2500 calories on days that I worked out! Wouldn't that make me gain weight? By the conventional "calories in < calories out" wisdom, yes. The wisdom is wrong. Since I started eating enough to keep my metabolism happy, I have actually lost weight and inches while becoming healthier. Most importantly, now that my metabolism is happy and doesn't think I'm running out of food, I can create a small deficit to encourage fat loss. My metabolism won't panic if I drop to 2200 calories, and my physiological processes will actually work in my favor.
I asked a few other people who use this program what changes they've noticed in their lives since they stopped fighting their metabolisms. A very common answer, especially among women, is that they don't get sick as often. Almost everybody said that they have more energy. A handful of people have even been able to reduce their dosage of certain medications, like thyroid medicine, since they got their metabolisms straightened out.
Not everybody buys into this philosophy, and that's OK. Different programs work for different people. But misinformation about "inevitable biological realities" will only serve to make people more unhealthy. Yes, losing weight can be a battle against biology if done incorrectly. And yes, some of us are biologically inclined to carry a little extra weight in certain parts of our bodies; my butt and thighs will never be small, no matter how careful I am about my eating habits. However, when researched and interpreted correctly, biology can be an ally in the fight against obesity and its frequent comorbidities.
The human body wants to thrive, and it will thrive when treated well. What we can conclude from the Fothergill, et al., study on The Biggest Loser is that unsustainable diets and extreme workout regimens are not treating the body well. They are unrealistic, unpleasant, and unkind to the bodies of the people enduring them. Weight loss methods that fight the body's desire to protect us from starvation are so unhealthy that they can damage the body's ability to recover. That is what we can conclude from this study, and it is unethical to draw on these conclusions to speculate that all weight loss is damaging.
As a final caution, be wary when reading an untrained person's interpretation of a scientific paper. Statistics can be tricky, and the publications are often laden with field-specific jargon. People get degrees specifically in science writing because of the nuanced nature of the field. Even though I have a Bachelor's degree in biology and a Master's degree in the research-rich field of public health, I still read papers multiple times to make sure I understand their conclusions.
As I was reading the internet's reaction to the Fothergill paper, I realized that the reports were so skewed that I just needed to go straight to the source. Data will not lie, but people will, even if it is unintentional. A person reporting on a physiological phenomenon, for example, should have some knowledge of the field before they try to analyze and condense information to share with the public. They should especially know that one study does not prove anything. It's just responsible scientific journalism.