As if the Millennial generation didn’t have enough going against — from poorer job prospects to more expensive education — a recent study reported in The Atlantic has found that young people in the 21st century are less likely to lose or maintain weight than previous generations — even when they eat and exercise the same.
The authors examined the dietary data of 36,400 Americans between 1971 and 2008 and the physical activity data of 14,419 people between 1988 and 2006. They grouped the data sets together by the amount of food and activity, age, and BMI.
They found a very surprising correlation: A given person, in 2006, eating the same amount of calories, taking in the same quantities of macronutrients like protein and fat, and exercising the same amount as a person of the same age did in 1988 would have a BMI that was about 2.3 points higher. In other words, people today are about 10 percent heavier than people were in the 1980s, even if they follow the exact same diet and exercise plans.
“Our study results suggest that if you are 25, you’d have to eat even less and exercise more than those older, to prevent gaining weight,” Jennifer Kuk, a professor of kinesiology and health science at Toronto’s York University, said in a statement. “However, it also indicates there may be other specific changes contributing to the rise in obesity beyond just diet and exercise.”
Note that the study utilized Body Mass Index (BMI), the accuracy of which is questionable. But if the findings are true, it has some pretty big implications about how much our social, dietary, and physical environments have changed, and what impact that is having on human health.
While the researchers are pretty cautious about what exactly accounts for this generational disparity, they mention three likely culprits.
First, people are exposed to more chemicals that might be weight-gain inducing. Pesticides, flame retardants, and the substances in food packaging might all be altering our hormonal processes and tweaking the way our bodies put on and maintain weight.
Second, the use of prescription drugs has risen dramatically since the ’70s and ’80s. Prozac, the first blockbuster SSRI, came out in 1988. Antidepressants are now one of the most commonly prescribed drugs in the U.S., and many of them have been linked to weight gain.
Finally, Kuk and the other study authors think that the microbiomes of Americans might have somehow changed between the 1980s and now. It’s well known that some types of gut bacteria make a person more prone to weight gain and obesity. Americans are eating more meat than they were a few decades ago, and many animal products are treated with hormones and antibiotics in order to promote growth. All that meat might be changing gut bacteria in ways that are subtle, at first, but add up over time. Kuk believes the proliferation of artificial sweeteners could also be playing a role.
I would also add that the high rates of anxiety and depression resulting from tougher economic times probably play a role, too; stress and sleeplessness are well documented contributors to weight gain, and a large proportion of young people report chronically experiencing these problems.
As in so many other studies about the causes of weight gain, it appears that the contributing factors are complex and poorly understood, involving a confluence of hormonal, dietary, and environmental influences we are just starting to understand. Hence why the study cautions about the prevailing negative attitude towards the physically unfit.
The fact that the body weights of Americans today are influenced by factors beyond their control is a sign, Kuk says, that society should be kinder to people of all body types.
“There’s a huge weight bias against people with obesity”, she said. “They’re judged as lazy and self-indulgent. That’s really not the case. If our research is correct, you need to eat even less and exercise even more” just to be same weight as your parents were at your age.
As someone who has endured a lifelong struggle to maintain a healthy weight, I never really considered whether or not my difficulties were part of a larger generational milleui. Being fit and healthy was always supposed to be a difficult endeavor, not least because it runs somewhat contrary to our biology (humans evolved to store fat at all costs, for example). But what happens when humans struggle to adapt to totally new diets and conditions? Our species is already taller and larger in overall mass than it was just a couple of centuries ago; how different will physically be another century or two from now?
What are your thoughts?