A study published in 2016 by the journal Obesity Research and Clinical Practice found that adults today have a more difficult time maintaining the same weight as adults 20 to 30 years ago. The study accounted for levels of exercise and food consumption.
The researchers looked at the dietary data of 36,400 Americans between 1971 and 2008 as well as the physical activity data of 14,419 people between 1988 and 2006. They grouped the data sets together according to age, BMI, activity, and food.
The results surprised them. They found some very specific correlations. They looked at a given individual in 2006 who ate the same amount of calories, took in the same amount of macronutrients like fat and protein, and exercised the same amount as a similar individual did in 1988. They discovered that this individual would have a BMI that was 2.3 points higher.
Americans today are about 10% heavier than people in the 1980s, even following the same exact exercise plans and diets!
“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.”
However, scientists are not certain what changes may also be contributing to the obesity epidemic. Kuk suggested that 3 different factors may be making it harder for adults to maintain healthy weight and BMIs.
One factor is that people face greater exposure to chemicals that may be weight-gain inducing. Flame retardants, pesticides, and chemicals in food packaging may be altering our hormonal processes and changing the way our bodies put on and maintain weight.
Another factor is the dramatic rise in the use of prescription drugs since the 70s and 80s. For instance, Prozac was released in 1988. It was the first widely prescribed SSRI, and now antidepressants are one of the most commonly prescribed drugs in the U.S. Many depressants have been linked to weight gain.
Lastly, Kuk and other study authors believe that the microbiomes of Americans may have been significantly altered between the 1980s and now. It is accepted that some types of gut bacteria make a person prone to weight gain and obesity. Plus, Americans are eating more meat than several decades ago. Many livestock received treatments of hormones and antibiotics to promote growth and prevent disease. This increase in meat from treated livestock may be altering gut bacteria that appears subtle at first. However, it may accumulate over time. In addition, Kuk believes the increase in artificial sweeteners may also play a role.
The fact that the body weights of Americans today may be influenced by factors they cannot control may be a sign that society should not only be kinder to those who are overweight but also take a deeper dive into the causes.
“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 the same weight as your parents were at your age.