A study published in the journal Nature Medicine has found that “eating less and exercising more” may actually be good advice as we age — because it turns out that we have decreased fat turnover as we age. If we eat the same amount as we always have and don’t increase the amount we exercise, we will end up gaining approximately 20% over a 10-15 year period.
Until recently little was known about fat turnover — which is the storage and removal of fat from adipocytes (fat cells). A 2011 study showed that during the average ten-year lifespan of human fat cells, the fat in them (triglycerides) turns over six times, in both men and women, and that when people are obese, the fat removal rate decreases and the amount of fat as triglyceride stored each year increases. What we didn’t know until now is what happened to fat turnover as we age. This follow-up study headed by the same lead researcher as the 2011 study explored this issue, as well as differences in fat turnover after people have bariatric surgery which helps explain why some people regain their weight after weight loss, where as others don’t.
Fat turnoveris a difference between the rate of fat uptake into fat cells and the fat removal rate. High fat storage but low fat removal is what results in the accumulation of fat and in obesity. The “bad news” of this new study is that fat accumulation due to decreased fat turnover is what happens as we age, leading to accumulation of fat. That is, even if we don’t eat more or exercise less than previously, we will store more fat — which can result in as much as a 20% increase in body weight over 13 years.
“Those who didn’t compensate for that (i.e. decrease fat turnover) by eating less calories gained weight by an average of 20 percent”.
Researchers from the University of Uppsala in Sweden and the University of Lyon in France studied the fat cells of 54 men and women over an average 13 year period  and regardless of whether the subjects gained weight or lost weight, they had a decreased fat turnover.
Since fat turnover is decreased as we age, to prevent weight gain we need to take in less calories than we used to, even if we are just as active.