Exercise is one of the first strategies used to treat obesity-related health problems like type 2 diabetes and other cardiovascular diseases, but scientists don’t understand exactly how it works to improve metabolic health.
To that end, researchers at the University of Michigan studied the effects of three months of exercise on obese people and found that exercise can favorably alter abdominal subcutaneous fat, the fatty tissue just under the skin, in ways that can improve metabolic health—even without losing weight. by weight.
Surprisingly, moderate and high-intensity exercise produced the same positive changes in adipose tissue composition and structure, and fat cells shrank slightly even without weight loss, said lead researcher Jeffrey Horowitz, UM professor of kinesiology.
The findings appear in The Journal of Physiology. Co-first authors are UM doctoral student Cheehoon Ahn and Ben Ryan, a UM postdoctoral research fellow who is now at the U.S. Army Research Institute of Environmental Medicine.
Exercise changed the way fat looked and behaved
The study aimed to better understand the effects of exercise on metabolic health in obese people. Thirty-six obese adults were assigned to either a moderate-intensity exercise group (45 minutes, 70% of maximum heart rate) or a high-intensity exercise group (10 one-minute intervals at 90% maximum heart rate, interspersed with 60 seconds of active recovery with low intensity).
Blood samples and abdominal fat biopsies were collected the day after the end of the 12-week sessions and again three days later. There was no exercise between these tests. The results for both exercise groups showed several structural changes in adipose tissue, including slightly smaller fat cells and more of them, an increased type of collagen, increased capillary density, and changes in proteins that regulate body fat remodeling.
Horowitz said many of the changes in factors regulating body fat remodeling observed one day after exercise were no longer significant by day 4 of testing, and this underscores the importance of regular, sustained exercise.
The improvements disappeared when the training stopped
Many adaptations to exercise training are effective in allowing a person to exercise longer or more intensely, Horowitz said.
However, most of the benefits of exercise that improve metabolic health in people at risk of metabolic complications or those who have metabolic diseases arise from the response to each exercise session—and these responses to exercise are relatively short-lived, often lasting only the very few days. That’s one of the big reasons why it’s so important to be physically active most days.”
Jeffrey Horowitz, UM professor of kinesiology
The finding that moderate- and high-intensity exercise produces similar responses may be good news for people who prefer to avoid the more demanding high-intensity interval training, or HIIT.
Moderate exercise is just as beneficial as HIIT
“Our findings show that the options are open,” Horowitz said. “The similar response between HIIT and more conventional moderate-intensity exercise was among the bigger surprises for us. Impressively, we observed very similar responses despite the rather large differences in exercise stimuli (exercise time, kcal expended, intensity) between these two training programs.
While the findings aren’t related to weight loss, they are related to metabolic health and disease prevention in obese people, which in turn affects quality of life, Horowitz said.
“Although some of our favorable results were relatively short-lived, some were longer-lasting, such as adipose tissue capillary density and fat cell structure,” he said. “Therefore, we hypothesize that a physically active lifestyle may help protect people from developing some chronic metabolic health complications if or when they gain weight as they age, and the evidence strongly suggests that most of us, even regularly exercisers gain weight as they age.”
Horowitz said it’s important for people to understand that fat tissue is simply where our bodies store extra energy, and it’s not the reason people gain weight.
“Fat can only happen if you eat more calories than you expend. And in situations where we’re gaining weight, especially to the point where people are approaching or becoming obese, it’s ideal to have what’s called healthy adipose tissue in which to store that extra energy.
Several of the lab’s recent studies, and a new five-year NIH-funded project starting soon, focus on understanding how exercise can beneficially affect adipose tissue in ways that make it a safer haven for fat storage if and when people experience weight gain or weight regain.
Anne, K., et al. (2022) Exercise remodels subcutaneous adipose tissue in obese adults even without weight loss. Journal of Physiology. doi.org/10.1113/JP282371.