Men's Health July 16, 2026 0 Comments

The Surprising Scientific Reason Behind Why Some Men Secretly Embrace the Dad Bod After 40—And What It Means for Your Health

Ever wondered why that stubborn belly fat seems to have a VIP pass as you hit midlife? It’s not just about those extra slices of pizza or your weekend brewskis—science now shows it’s a cellular switch flipping on, encouraging your body to churn out brand-new fat cells as you age. Yep, turns out our old belief that fat cells just balloon bigger was a half-truth. This new insight shakes up everything we thought we knew about midlife weight gain—and better yet, it might pave the way for meds that hit fat gain at the root. Meanwhile, the good news? You’ve got real, actionable ways to fight back and reshape your body. Curious how your stem cells might be playing against you, and more importantly, how you can outsmart the process? Let’s get into the nitty-gritty. LEARN MORE

4 min read

Belly fat gets harder to avoid with age. Scientists once believed people gained weight more easily with age because existing fat cells would get bigger.
A study identified an age-related cellular switch that drives the creation of new fat cells in midlife.
Eating a mostly plant-based, unprocessed diet helps to keep the extra pounds off. And while there is nothing you can do to specifically target belly fat, a mix of cardio and resistance training can limit weight gain while reshaping your body composition.

AN UNFORTUNATE FACT of life: It’s easier to gain weight as you age. But science just made a leap in figuring out why—and it’s not about how many six-packs you knock back. Research published in the journal Science discovered a number of cellular changes occur that encourage you to produce new fat cells as you age.

That’s not actually bad news: It may lead to new types of meds that could keep weight from accumulating. And you can fight your (cellular) destiny. More on this below.

Why Belly Fat Expands With Age

PREVIOUSLY, SCIENTISTS THOUGHT that when people accumulated weight (especially around the midsection), existing fat cells just got bigger. But the new study found that new fat cells may be constantly created. A different mechanism of weight gain means researchers may be able to find different approaches for making it happen.

They figured it out by looking at a special category of stem cells, called adipocyte progenitor cells (APCs), that are found in fat tissue (yes, your fat contains stem cells). In youth and early adulthood, these cells stay as they are. But in adults, they have the potential to transform into fat cells and add to the number you already have.

Scientists used some complicated RNA sequencing to study each cell’s gene activity. But the TL;DR is that when they took stem cells from really old mice and injected them into the fat tissue of young ones, the number of fat cells they had shot up. Nothing happened when they put stem cells from young mice into other young mice.

They determined that something about age was making these APCs become highly active and aggressively start producing new fat cells.

“While most adult stem cells’ capacity to grow wanes with age, the opposite holds true with APCs. Aging unlocks these cells’ power to evolve and spread,” says Adolfo Garcia-Ocana, PhD, chair of the department of molecular and cellular endocrinology at City of Hope and study author. “This is the first evidence that our bellies expand with age due to the APCs’ high output of new fat cells.”

In addition, scientists saw that a signaling pathway unique to older mice gave another type of stem cell the go-ahead to create new fat cells, especially around the abdominal area.

What about humans? They looked at that, too. Well, sort of. Scientists didn’t inject older people’s fat into younger people, but instead replicated the process with human cells and found similar results to what they observed in mice.

Other Changes That Fuel Midlife Weight Gain

YES, YOUR CELLS are to blame for making weight gain easier as you get older. But it’s only part of the story.

Hormones and metabolism change too, says Mir Ali, MD, medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, California.

One notable hormone is testosterone. Weight and testosterone are closely linked. Production of the primary male hormone starts to decline after 30 and can make it easier to gain weight. Weight gain can also actively lower T levels because inside fat tissue is an enzyme called aromatase that turns testosterone into estrogen.

Then there are the decisions you make every day that contribute to the dad bod. Richard Siegel, MD, co-director of the Diabetes and Lipid Center at Tufts Medical Center and endocrinologist at Tufts Medicine Weight & Wellness Center–Stoneham, says guys in midlife tend to be less active and deal with more sleep disorders as they age. All of this can fuel weight gain.

How to Get Rid of Midlife Belly Fat

WHILE SOME GUYS might embrace the dad bod look, you have ways to fight it if that’s not your style. You know the usual: diet and exercise. But MH asked doctors specializing in obesity for more specifics on what works to get rid of midlife belly fat for good.

In terms of nutrition, Dr. Siegel recommends focusing on having as much of a plant-based, unprocessed diet as possible. “This does not have to be a vegetarian diet, though diets higher in red and processed meats have been associated with weight gain.” Now what about beer? The good news is that you don’t have to quit. Instead, he says men should be more mindful in how much they’re drinking. Not only can the liquid calories add up, people tend to snack more when intoxicated.

With exercise, the best plan of attack is a mix of aerobic and resistance training. Keep in mind that “there’s nothing you can do to specifically target belly fat,” Ali says. Instead, all-over fat loss is the goal if you’re looking to avoid a beer belly. With cardio, you would limit weight gain and resistance training would reshape your body composition. (Need a guide? Check out MH’s Dad Bod Shred Workout tailored toward busy dads.)

Lastly, don’t neglect the power of a good night’s sleep. When you continuously get less than seven to nine hours of sleep, your body doesn’t get a chance to fully recover. That translates to a slower metabolism, daytime fatigue that could deter you from exercising, and greater cravings for high-calorie foods. “Optimal sleep—quantity and quality—may help to avoid weight gain,” says Dr. Siegel.

All in all, this latest discovery may eventually lead to new medications to combat those pesky fat-promoting stem cells. But that may not be available for another couple of years. In the meantime, you’ve got options to banish belly fat today.

Korin Miller is a freelance writer specializing in general wellness, sexual health and relationships, and lifestyle trends, with work appearing in Men’s Health, Women’s Health, Self, Glamour, and more. She has a master’s degree from American University, lives by the beach, and hopes to own a teacup pig and taco truck one day.

Jocelyn Solis-Moreira, MS is the associate health & fitness for Men’s Health and has previously written for CNN, Scientific American, Popular Science, and National Geographic before joining the brand. When she’s not working, she’s doing circus arts or working towards the perfect pull-up.