An Obesity Doctor Reveals the Groundbreaking Truth About the Effect of Aging on Your Metabolism

A doctor of obesity medicine says you are not doomed to gain weight just because you're getting older, despite the myths around aging and metabolism.

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Separating metabolism facts from fiction—or misinformation, anyway—is tough. (Can you boost metabolism? Does drinking water really flush fat? Small meals, or big ones?) One of the most persistent myths goes something like: Metabolism plummets as we age, which is why we gain weight.

There’s good news on that front, thanks to a recent study that helped to set the record straight. Published in the peer-reviewed journal, Sciencedata from almost 6,500 people across 29 countries—ranging in age from eight days old to 95 years old—showed that metabolism doesn’t significantly drop until age 60. Metabolism is highest for infants and steadily drops by about 3% annually until age 20. From there, it plateaus and stays consistent for the next four decades. 

Despite the research, many people start to put on more weight in middle age, well before they reach their sixties. And a lot of them think metabolism is to blame. In a 2022 poll of 2,000 Americans (conducted in 2022 by OnePoll on behalf of science-backed weight care program Found), 35% of respondents called out “a slower metabolism” as a top indicator that they believe is a sign of aging. But what’s going on if it’s not metabolism that’s adding the extra pounds? 

As a medical doctor guiding patients on the journey from obesity through weight loss, here’s my list of the surprising causes for weight gain as you age…and, more importantly, simple steps you can take to turn things around.

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Your unique biology 

Hormones can fail to work correctly in ways that lead to weight gain. Some people lack the hormones that manage appetite or help the body to use and store energy. Or the body becomes resistant to those hormones.

There are other ways biology influences weight. Neurotransmitters that signal hunger and fullness in the brain may not do their jobs.

What to do: These biological issues are not ones you can solve with just lifestyle changes like diet and exercise. In fact, the genetic predisposition for obesity—now recognized as a chronic disease that often needs medical treatment—may be as high as 70%. If you need help achieving a healthy weight, find an obesity clinic that uses an evidence-based, comprehensive approach, or look for an obesity medicine specialist. 

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Lack of quality sleep

While there’s no evidence that sleep boosts your metabolism, there is evidence connecting lack of sleep to extra weight. One 2015 biology study published in the peer-reviewed journal Obesity concluded that even a few nights of bad ZZZs can cause your resting metabolic rate to dip. Other research, such as one February 2022 study in the Journal of the American Medical Association’s Internal Medicine, found that skimping on sleep may increase the hunger hormones—and trigger cravings for simple carbs (the sugary, bready stuff). Good news: When you improve sleep, your metabolism and hormones should level out.  

What to do: Prioritize sleep, aiming for seven to nine hours every night. Work backward from your wake time to make sure you’re getting into bed at a time that will give you enough sleep and stick to a consistent bedtime routine. Here are some ideas for winding down: 

  • Shut off your phone and all screens 30 minutes before bed
  • Do five minutes of yoga or meditation 
  • Spend a few minutes journaling
  • Read 

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Stress 

Stress can happen even more often as we get older and responsibilities pile up. There’s evidence that stress may trigger hormones that can prompt fat cells to form. And when we don’t address it, we may turn to food to self-soothe.   

What to do: Take time for self-care to keep stress levels down, which will also go a long way toward helping you make healthier lifestyle choices. Schedule daily breaks to do something that makes you feel good, whether that’s a walk in nature, eating lunch outside, or pausing to take five deep breaths whenever you feel your shoulders tense up. 

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Rekha Kumar, MD, MS
Rekha Kumar, MD, MS is an endocrinologist, obesity medicine specialist and the chief medical officer of Found, a clinician-led weight care clinic. She has authored papers and textbook chapters on the medical management of obesity and served as the former medical director of the American Board of Obesity Medicine.