Experts say the new research shows exercise may be the “biggest contributor” to obesity in the U.S. The study also suggests that the same process could explain why people who exercise are more likely to become obese in later life.
“The main thing is that exercise is an important and safe activity,” said Dr. Robert R. Smith, an associate professor of preventive medicine at the University of Southern California.
“Exercise, in our experience, has been shown to be very safe, relatively inexpensive, and effective for obesity prevention and treatment.”
The new study, which looked at more than 3,200 adults, found that people who exercised less than two hours a week had about two-thirds the risk of becoming obese, while those who exercised more than three hours a day had about four-fifths the risk.
Exercise may be more likely than smoking, diet, or obesity to increase the risk, the researchers said.
“It’s not just that exercise induces inflammation, which we all know is associated with obesity, but also that exercise and exercise-induced inflammation are associated,” said David Spiegelhalter, an assistant professor of pediatrics and director of the University Center for Pediatric and Adolescent Medicine at the Johns Hopkins Bloomberg School of Public Health.
Exercise increases inflammation in the pancreas, and researchers have long suspected that exercise may lead to insulin resistance, a condition that reduces insulin levels in the body.
But there is a problem.
Obesity rates among adults have been declining for decades, but in the past decade, rates have skyrocketed in the most obese adults, according to a study by researchers at the Harvard T.H. Chan School of Engineering and Applied Sciences.
The researchers said this increase in obesity was “not due to changes in the population itself, but rather to changes at the level of the individual.”
This is the first study to look at the role of exercise in obesity.
In the new study published in the New England Journal of Medicine, researchers analyzed data from the National Health and Nutrition Examination Survey, which was conducted in 2006.
They also looked at data from more than 1,500 participants in the National Longitudinal Study of Adolescent Health.
For each participant, they analyzed the amount of exercise they did over the course of the year, and compared this amount to their body mass index, a measure of body fat.
Researchers looked at the differences in BMI and the amount they exercised for the past 12 months, as well as the number of people they saw daily exercising, whether they were physically active or not.
The results showed that the more exercise participants did, the more likely they were to be obese.
“We see a lot of overlap between the number and the severity of exercise,” said study co-author Dr. David M. Katz, a professor of public health and epidemiology at the Columbia University Mailman School of Global Health.
“In this population, people who are more active and less active, those who are physically active are more obese.
That’s the main finding of the study.”
The study found that the amount people exercised for each month also had a direct impact on their risk of obesity.
“People who were more physically active had higher BMIs,” said Smith.
“Those who were less active had lower BMIs.”
Exercise, however, had a less positive effect on weight loss.
In fact, people in the study who exercised at least three hours daily had lower rates of weight loss than people who did not exercise, and those who did exercise were also less likely to be overweight.
But exercise is not the only factor that is associated in obese adults.
Other factors that may be contributing to the development and progression of obesity include a higher percentage of sedentary people and a lower socioeconomic status, researchers said, which may also increase the amount and severity of inflammation in that person’s pancrease.
“There’s not a silver bullet that can prevent obesity in its early stages,” said Spiegelhalters co-researcher Dr. Laura T. Tippett.
“But exercise is a good place to start.”