3 myths about metabolism could be holding you back

CNN

6 hours ago

EDITOR'S NOTE: The podcast Chasing Life With Dr. Sanjay Gupta explores the medical science behind some of life's mysteries big and small. You can listen to episodes here.
(CNN)— Think speeding up your metabolism is key to losing weight? Metabolism has grown into one of the biggest buzzwords in the wellness industry — a tricky code that, if deciphered, is believed to unlock the secrets of weight loss and overall health.
Despite the term's ubiquity, one scientist says many people don't understand much of how this basic bodily process works.
'They think it has something to do with how much food we can eat without gaining weight or something like that,' Dr. Kevin Hall told CNN Chief Medical Correspondent Dr. Sanjay Gupta recently on his podcast, Chasing Life.
Hall wants to elevate metabolism for different reasons. 'Metabolism is just this incredible biochemical process that basically turns the food that we eat and the oxygen that we breathe into essentially … everything we are and everything we do,' he said.
A leading nutrition and metabolism scientist, Hall is well-known for his research on contestants from the reality show 'The Biggest Loser' that helped explain what set participants who kept the weight off apart from those who gained it back.
He spent more than two decades at the National Institutes of Health. His later work on ultraprocessed foods investigated its link to obesity, including one study that demonstrated it actively caused participants to overeat.
Hall announced his early retirement and exit from NIH in April, citing censorship of how his research findings were communicated. He's now coauthor of the new book 'Food Intelligence: The Science of How Food Both Nourishes and Harms Us' alongside journalist Julia Belluz.
Metabolism and weight loss enter conversations arm in arm, but this, according to Hall, can be reductive.
'I just find it incredibly frustrating sometimes that this idea of metabolism, this really beautiful physiological process that is so fundamental to life, is kind of talked about as, 'Oh well, if you take this supplement, you can boost your metabolism and lose weight,'' he explained to Gupta.
You can listen to the full episode here.
Is a faster or higher metabolism really the highway to weight loss? Hall is here to set the record straight, highlighting three misconceptions about metabolism that show there is more to it than meets the eye.
One common belief is that a slower metabolism results in a higher body weight. But mostly, Hall said, the opposite is true.
'Generally, larger people have faster metabolisms than smaller people,' he told Gupta.
Hall attributed the pervasiveness of this myth to the way researchers designed early metabolism studies. Scientists initially tried to match up participants' caloric intake to their weight, but they didn't account for the fact that these calorie counts were self-reported.
It turned out that those with obesity often underreported the number of calories they ate to a larger degree than their leaner counterparts. This, Hall said, 'led people to a conclusion that, well, if they're eating less calories and they're maintaining their weight, then they must be burning less calories. And maybe the reason why they have obesity is because they have slow metabolisms.'
Modern technology now allows researchers to rely on data, not participants' own reports. 'When we actually directly measure people's metabolisms, people with obesity have higher metabolic rates on average than people who are lean,' Hall noted.
But the myth that we should be boosting metabolism to treat obesity has stubbornly persisted — and has at times led to deadly consequences. When Stanford University researchers discovered that the chemical compound 2,4-dinitrophenol, or DNP, increased metabolism levels in the 1930s, they enthusiastically promoted it as a safe and effective tool for treating obesity.
While DNP did boost metabolism, it also led to side effects that included blindness and death, causing federal drug regulators to quickly withdraw it from the market.
'Maybe,' Hall suggested, 'it shouldn't be too much of a surprise later to realize that with something so fundamentally important to life as metabolism, you can't just turn it up and turn it down with a pharmaceutical drug and not expect some pretty severe side effects, including death.'
Like weight, age might not affect metabolism as much as you may assume.
'It turns out that until you get to very advanced ages, we're talking 70s and 80s, it looks like our metabolic rate is roughly constant,' Hall said.
There are, of course, changes in the aging body that can impact metabolic rates.
People 'past the age of 30 or so,' Hall said, are 'tending to lose muscle mass or tending to lose lean mass, and they're tending to gain fat mass. And that alone is anticipated to result in a lower metabolism.' That's because lean muscle burns more calories than fat.
But it's these age-related changes — that are not inevitable — and not age itself, that influence one's metabolism.
'Once you get rid of that effect … it doesn't seem like there's a fundamental aging effect to slow metabolism as, as we get older,' Hall concluded.
A couple ways to combat the loss of lean muscle mass as you age is by engaging in twice-a-week strength training and getting enough protein in your diet (but no need to go overboard).
Another pillar of metabolism mythology is the idea that a slow metabolism is the enemy of continued weight loss. Interventions such as dieting are believed to slow metabolism to the point that you can't lose any additional weight.
But keeping your metabolism from slowing down isn't the key to sustained weight loss, Hall said. In fact, it's just the opposite.
'The people who are most successful at losing weight and keeping it off are the ones who sport the slowest metabolisms or the greatest reductions in metabolism,' he said. 'It's kind of like stretching a spring, right?'
The more intensely someone diets or exercises, the more weight they'll lose and the more their metabolism will slow down, he explained in his book.
Hall's research showed that a slower metabolism 'didn't seem to determine anyone's ability to lose weight or keep it off in the short or long run.'
By uncoupling metabolism from the weight loss conversation, Hall said he hopes everyone can appreciate the phenomenon for what it really is.
Misinformation about metabolism 'has really distracted people, I think, from the real beauty of what this is,' he told Gupta.
'It's harnessing the continuous flow of matter and energy in our food and in our breath and powering every cell in our body, as well as the bodies and cells of practically every organism that we have ever encountered,' Hall said. 'It's a fundamental component of life, and it's just incredibly fascinating.'
We hope these three insights help you understand your metabolism better. Listen to the full episode here. And join us next week for a new episode of Chasing Life.