Research & Education

New Research on Why We Gain Weight as We Age

It’s no secret that losing weight is easier said than done. While some people seem to effortlessly maintain a healthy weight throughout their life, for others it’s a lifelong struggle that starts in toddlerhood and only gets more difficult as they age. Weight gain in middle age and beyond is so common that books have been written specifically to help people get rid of their “middle-aged middle.” Using data from 2016, the US Centers for Disease Control and Prevention (CDC) estimated that the prevalence of obesity is staggering: close to 40%, affecting over 93 million Americans. Research from Sweden last month sheds light on why the dreaded battle of the bulge doesn’t only seem to get harder to fight as we age—it actually is harder.

The study, “Adipose lipid turnover and long-term changes in body weight,” determined that during the aging process, adipose tissue holds on more tightly to the fat stored within it—that is, it’s more difficult to liberate stored body fat and burn it. The study authors wrote, “Lipid removal rate decreases during aging, with a failure to reciprocally adjust the rate of lipid uptake resulting in weight gain.” In other words, the release of stored fat from adipocytes is reduced as we get older but most of us don’t compensate by eating less or by engaging in physical activities that can increase our metabolic rate or at the very least slow the decline.  

This is more than a case of simply eating less and moving more, though. According to one of the study authors, “…processes in our fat tissue regulate changes in body weight during ageing in a way that is independent of other factors.” It seems that this decline in release of stored body fat will happen regardless of someone’s healthy habits, but perhaps these healthy habits can make this unfortunate and apparently inevitable slowdown slightly more graceful.

It’s easy to say “eat less,” but very hard to actually do. One way to potentially attenuate the effects of the decrease in adipose lipid turnover is to prioritize foods that are satiating yet low in overall energy density—things like lean proteins and low-starch vegetables. Filling up on lean beef, pork, seafood, and chicken plus a pile of lettuce, broccoli, cauliflower, zucchini, cucumber, and other vegetables high in water and fiber but low in carbs and calories is one way to eat more in volume while consuming less in energy density.  

Cutting back on refined carbohydrates may be particularly beneficial as we age. Not everyone needs a strict ketogenic diet in order to ward off weight gain as the years pass, but chronically elevated insulin is a major factor in obesity and difficulty losing body fat. Insulin is far more than a “blood sugar hormone.” Apart from its role facilitating cellular glucose uptake—which is actually one of insulin’s lesser tasks—a primary job for this hormone is inhibiting lipolysis. Insulin is directly inhibitory to the release of fatty acids from adipose cells, mostly via inhibition of the enzyme hormone-sensitive lipase, which is responsible for hydrolyzing triglycerides to free up their constituent fatty acids. (In order to “burn” fat, the fatty acids first have to be separated from the triglyceride molecules they’re stored in.) In individuals with chronic hyperinsulinemia—a massive epidemic that goes far beyond type 2 diabetes and metabolic syndrome—it can be nearly impossible to have a steady flow of fat coming out of fat cells. Insulin essentially keeps it locked in. Perhaps this is why one researcher said that with regard to weight loss, “the lowering insulin levels is the sleeping giant in patient care.”

Stressful situations typically provoke the release of catecholamines (e.g., epinephrine and norepinephrine) that induce lipolysis partly by activating hormone-sensitive lipase. However, elevated insulin has been shown to inhibit this activation, meaning that insulin appears to outweigh (no pun intended) the effects of catecholamines when it comes to releasing stored fat. Perhaps this is why some people seem to lose weight when under stress while others gain; maybe those among us who tend toward hyperinsulinemia are the ones who gain weight from merely looking at cupcakes. 

The tired old advice to “eat less, move more” might work for some, at least temporarily, but as a long-term strategy, it’s been known to backfire big time. Dieting for fat loss—particularly if it’s approached through drastic caloric restriction combined with overzealous exercise—is known to induce a decline in metabolic rate. This may be a kind of protective mode the body engages in order to prevent breakdown of critical muscle mass and other vital tissue. Researchers have called this “famine response hypothyroidism,” and it may be why a demanding and disciplined approach to fat loss that worked at one time eventually stops working even when an individual continues to adhere to their previously successful regimen. (It’s also the likely explanation for why most contestants from the TV show The Biggest Loser regained their lost weight, and some gained even more.)

Even under a more reasoned and gentle approach to fat loss, it’s not uncommon for some degree of metabolic slowdown to occur. However, a 2018 study from Harvard University and Boston Children’s Hospital showed that low carbohydrate diets may have a slight edge here. Researchers found that compared to subjects on a diet high in carbohydrate, those on a low carb diet nearly equal in protein had a significantly greater increase in total energy expenditure.

Maintaining metabolic rate or even slightly increasing it might be the key to sustaining a weight loss over the long term. Anything that can help make this easier should be given serious consideration. As difficult as it is to lose body fat initially, maintaining that loss over the course of years and even decades is usually an even bigger challenge, particularly when, as the Swedish study showed, our own adipose cells are working against us. Beyond the potential effects of a diet lower in carbs, there may also be a role for thermogenic herbs and other compounds in facilitating weight loss and maintenance, such as garcinia cambogia, conjugated linoleic acid (CLA), and green tea extract.