Mitochondria are effectively power plants, hundreds of them working in every cell to produce chemical energy store molecules to power cellular processes. Mitochondrial function declines with age, unfortunately, for underlying reasons that appear to involve gene expression changes that reduce the effectiveness of mitochondrial quality control mechanisms. This has profound effects on tissue function throughout the body, and is an important contribution to degenerative aging. Here, researchers discuss some of the effects on fat tissue specifically.
Researchers looked at the role of age and physical training in maintaining fat tissue function. Specifically, they studied mitochondria, the tiny power plants within fat cells. Mitochondria convert calories from food to supply cells with energy. To maintain the life processes within cells, they need to function optimally. The researchers compared mitochondrial performance across a range of young and older untrained, moderately trained and highly exercise trained men. The results demonstrate that the ability of mitochondria to respire - i.e., produce energy - decreases with age, regardless of how much a person exercises. "Although mitochondrial function decreases with age, we can see that a high level of lifelong exercise exerts a powerful compensatory effect. In the group of well-trained older men, fat cells are able to respire more than twice as much as in untrained older men."
Just as a car engine produces waste when converting chemical to usable energy, so do mitochondria. Mitochondrial waste comes in the form of oxygen free radicals, known as ROS (Reactive Oxygen Species). ROS that isn't eliminated damages cells and the current theory is that elevated ROS can lead to a wide range of diseases including cancer, diabetes, cardiovascular disease, and Alzheimer's. Therefore, the regulation of ROS is important.
The group of older people who train most form less ROS and maintain functionality to eliminate it. Indeed, their mitochondria are better at managing waste produced in fat cells, which results in less damage. Therefore, exercise has a large effect on maintaining the health of fat tissue, and thereby probably keeping certain diseases at bay as well. The researchers can also see that the older participants who exercised most throughout life have more mitochondria, allowing for more respiration and, among other things, an ability to release more of the fat-related hormones important for the body's energy balance.