Weight gain as we age seems almost inevitable even among individuals who are extremely conscientious about their daily caloric intake. The most common explanation is that activity levels decline with age and consuming the same amount of food per day with less activity results in extra pounds. What is both puzzling and frustrating is that older individuals gain weight even when there is a reduction in food intake commensurate with any reduction in activity. A recent study may explain why and provides important clues on how to prevent age-associated weight gain.
Contrary to popular belief, our fat cells are quite active metabolically. Because our energy needs are always changing, there is an ongoing dynamic between lipid storage and lipid release. Fat cells sense our energy needs and respond accordingly. When energy consumption exceeds energy needs, fat cells store lipid. Conversely, when energy needs are high, fat cells release lipid so that it can be converted into energy (to drive muscle function as an example). In this recent study, investigators looked at changes in fat cell function as we age. They found the mechanism to release lipid for energy was blunted as we age but there was no change in the fat cell's ability to store lipid. This explains that even when individuals reduce their daily caloric intake to compensate for reduced activity they still gain weight.
However, there is good news for endurance athletes. Multiple studies have shown exercise stimulates fat burning, the mechanism responsible for release of lipid from fat cells so that it can be converted into energy. In other words, exercise overcomes the natural aging process and helps maintain normal function of your fat cells.