Many of us may not realize that body fat can be metabolically healthy – or vice versa – regardless of a person’s weight or shape.
“Healthy fats are not about how much fat” a person carries, said Jeffrey Horowitz, a professor at the University of Michigan who studies exercise and metabolism. He said it has to do with how well those fats function. “A person with healthy fat is much better off than someone with the same percentage of body fat and unhealthy fat.”
What distinguishes healthy fats from imbalanced fats, Horowitz said, is the size of the fat cells. “The more small fat cells there are, the better,” he said.
In particular, you don’t have to lose weight or fat to make the body fat you already have more metabolically healthy.
Why is the size of fat cells important?
The large fat cells are already filled with fat, he said. They can’t store much and tend to leak some of their stuffed contents into the bloodstream as fatty acids. From there, the fatty acids rush toward other organs, such as the heart, muscles, or liver. Fatty, marbled liver, muscle or hearts are not desirable (unless calves are raised).
On the other hand, small fat cells can mainly expand It swallows fat from your blood. You want the fat to stay inside the fat cells, Horowitz said.
Healthy fat cells also contain packets of active mitochondria, which are the powerhouses of any cell. Mitochondria convert oxygen and food into cellular energy. In general, the more mitochondria, the healthier and more resilient any cell, including fat cells.
Finally, healthy fat tissue is filled with blood vessels, to carry oxygen and nutrients to the fat cells, along with battalions of other cells, most closely related to immunity, that help fight inflammation. Without adequate blood supply and immune protection, fatty tissues often become inflamed and scarred and release substances into the bloodstream that trigger similar and unhealthy inflammation elsewhere in our bodies, even in people who are not overweight.
How exercise can reshape your fat cells
Until recently, though, scientists weren’t sure whether or not our fats could change. That is, they knew that healthy fat tissue can deteriorate, filled with large, leaky cells, dysfunctional mitochondria, and inflammation.
But whether this process can be reversed or slowed has remained unclear. Some studies in recent years involving rodents have been encouraging, indicating that physically active animals have more body fat than sedentary rodents, even if they are all obese by rodent standards.
But we are not guinea pigs and many questions remain about the malleability of our body fat.
a study The publication in June brought a glimmer of clarity, though. In the study, researchers at the University of Copenhagen in Denmark took a biopsy of abdominal fat from young, sedentary men, older men who did not exercise, and older men who were physically active, most of whom were long-term and frequent cyclists.
Fat cells from sedentary older men showed relatively poor mitochondrial health, with fewer mitochondria than in young fat and lower energy produced by each mitochondria. But the fat cells of physically active men had a lot more mitochondria, even more than the fat tissue of young men, so their fat cells, in general, are better fueled. Adipose tissue also showed lower initial signs of inflammation than fat from inactive men, whatever their age.
“Exercise training means more mitochondria and better functioning mitochondria,” said Anders Gudiksen, professor of cell biology at the University of Copenhagen, who led the study.
But for anyone who hasn’t had the foresight to be a lifelong cyclist, another new study offers hope that starting to exercise now, no matter how long you stay in motion, can quickly improve your fat fitness.
for new study, published in the Journal of Physiology and supervised by Horowitz, researchers took a sample of fatty tissue from 36 obese men and women, then asked them to ride a stationary bike at a moderate pace for 45 minutes or more intensely for 20 minutes of exercise. Four times a week for 12 weeks.
The volunteers’ diets were carefully monitored, so as not to lose weight. Contrary to this, Horowitz said, the changes in adipose tissue may be caused by weight loss, not exercise.
But without losing weight, the volunteers who exercise can still reproduce their fat. They ended up with a greater number of small fat cells, as well as more capillaries to nourish those cells. Their fat tissue also has fewer biochemical signs of inflammation and fewer symptoms of scarring and stiffness around the fat cells.
These effects were seen, whether the volunteers rode moderately or hard. “Intensity didn’t matter,” Horowitz said, though they were energetic.
In the short term, these modifications should make fat tissue better able to gobble up and store any extra calories someone ingests with large meals during the holidays, a scenario that doesn’t necessarily mean weight gain, Horowitz said. Usually stored temporarily, this fat is quickly converted into energy for other tissues, such as muscle. But in the meantime, he said, those fats are best stored in fat cells, not the liver or arteries.
Horowitz said the long-term effects of exercise and fat revolve around inflammation, whether and how metabolically healthy fats contribute to a metabolically healthy body, even — and perhaps especially — if people are obese.
He said we need more research to better understand exactly what constitutes healthy fats and what types and amount of exercise they generate or maintain. But it already seems clear, he said, that movement benefits fat, as well as the rest of the body, providing an extra reason to ride, walk, jog, swim or, whatever method you choose, to be active today.
Do you have a fitness question? E-mail YourMove@washpost.com We may answer your question in a future column.