The ‘dad bod’ is not inevitable, even if evolution helped make it happen

What if evolution led us to the “dad bod”?

In humans’ evolutionary past, a drop in testosterone may have helped men adjust to and increase their involvement in their children’s lives, says Lee Gettler, an anthropologist who has studied the science of men’s changing bodies. But lower testosterone can also drive a softer, less toned, paunchier physique, a.k.a. a dad bod.

“The biological traits that were beneficial in the environments we lived in hundreds of thousands or millions of years ago are now mismatched to aspects of our current environment,” says Gettler, director of the Hormones, Health and Human Behavior Lab at the University of Notre Dame. Meaning that lower testosterone helped those early hunter-gatherers become better fathers - but at a time when life involved lots of physical activity and less than abundant food.

“The important thing to message to dads about this is that we just need to keep trying to work hard to the best of our abilities to take care of our bodies,” Gettler says. “It’s hard when you have to try to get enough sleep and you have to try to get enough exercise and you have to try to not finish the chicken nuggets on the kid’s plate, even though you don’t want to waste them at the restaurant.”

In a study Gettler and colleagues conducted in the Philippines, “we found that new dads with newborns have very substantial drops in their testosterone, on average, which could reflect changes during pregnancy or immediately in the period after their babies are born.”

The men in the study were in their 20s, and their testosterone went down about 25 percent on average. “That’s a big biologically meaningful change,” Gettler says. “Far greater than what might be simply due to aging, which might only drop testosterone levels 10 percent per decade after the 30s.”

In a similar article, published in Evolution, Medicine and Public Health in 2017, Gettler used U.S. population data to show that American men who were partnered and living with children had substantially greater body fat, particularly around their waists, than single men not living with children.

The difference in body fat between the two groups - the dad-bod phenomenon - was explained by their lower testosterone levels, Gettler wrote. Age-matched single men, not living with babies or young children, had higher testosterone, on average. Studies have also shown that men’s brains change with fatherhood.

As for why those evolutionary ancestors saddled today’s fathers with a steep hormonal drop, Gettler says it’s about priorities.

“The idea is that that transition with this decline in testosterone, whether you’re talking about bird fathers or human fathers or other mammalian fathers, helps to shift priorities away from mating effort, away from competition and more toward partnering with the mother to help raise demanding offspring,” he says.

But humans have also evolved, Gettler explains, such that fathers have the capacity to be involved in a range of ways that are costly in terms of time, energy and resources.

People often have less time to exercise as they start families and dive deeper into work, typically in their 30s.

“Generally, sometime around the age of 30, a sedentary person starts to lose muscle at about the rate of a half percent per year,” says Brad Schoenfeld, an expert on muscle physiology and a professor in exercise science at Lehman College in the Bronx. “That’s usually in that dad-body age range, so certain parts will begin to sag, and any addition of extra body fat in the area only accentuates the effect.”

But it can also be an important time to emphasize men’s health and well-being.

“I think it is important to shift the exercise narrative away from a focus on weight loss to a focus on health and well-being gain,” says Shelley Keating, an obesity researcher and senior lecturer at the University of Queensland’s School of Human Movement and Nutrition Sciences in Australia.

“For dads, or anyone for that matter, looking to make positive changes, it’s important to understand that most health benefits of exercise occur irrespective of weight change,” Keating adds. In other words, it’s not all about what you see when you step on the scale.

Avoiding or unraveling the dad bod takes exercise and healthy diet choices, and before you start, it’s a good idea to consult qualified professionals.

“I always like to indicate that this is best supported by a doctor or dietitian to make sure no essential food groups are being cut and micronutrient requirements are being met,” Keating says.

Men should also be realistic and not too hard on themselves. “Try and make your healthiest choices and your best choices as often as you can, and at the same time, recognize you may not always be able to do that,” says Craig Garfield, a pediatrics professor at Northwestern University’s Feinberg School of Medicine and an attending physician at Lurie Children’s Hospital of Chicago. Garfield also founded the first public health survey of fathers in the perinatal period. The most important thing is for new dads and moms to take care of themselves, he adds, because that’s ultimately best for the baby, too.

For most men, an hour or two of strength training a week is enough to push back against the dad bod, Schoenfeld says.

Total body exercise: Schoenfeld recommends working all the major muscles of the body in the same workout session, preferably with exercises that involve multiple joints. This includes push-ups, squats, pull-ups, lunges and overhead presses. Perform a minimum of one leg-pressing exercise (e.g., squats), one upper-body-pulling exercise (e.g., pull-up) and one upper-body-pushing exercise (e.g., bench press) per week. You can use machines or free weights. Aim for a minimum of four weekly sets per muscle group a week.

Cardiovascular training: When the goal is getting healthy and losing fat, exercise at or even below the current physical activity guidelines of 150 to 300 minutes per week of moderate intensity exercise or 75 to 150 minutes per week of vigorous intensity exercise can help shed abdominal fat, Keating says. For weight loss via aerobic exercise alone, more than 60 minutes at least five days a week is recommended.

Time crunch training: When finding time to exercise is a problem, low-volume, high intensity interval training (HIIT) programs allow a shorter exercise session with the same gain or better. But before starting HIIT, older adults and anyone at risk of cardiovascular disease, including those starting exercise after a period of being inactive, should get medical clearance to do so.

Nutrition: Generally, to lose weight, you should eat approximately 500 calories less than normal per day, Keating says. The diet should focus on whole foods and improving diet quality. As with exercise, the sustainability of the diet is a key for long-term weight-loss success, she says. Improving your diet quality can improve your heart health even in the absence of weight loss.