Diet Beats Exercise for Longevity
Clearly, we should not need to make an either-or choice, but scientists wanted to know which was better for a long life: calorie restricted diet, or exercise? The research clearly shows caloric restriction is more beneficial for life extension than exercise.
The first caveat is that they were looking at mice, and however similar the mammalian physiology can be at times, mice are not humans. Second, note that this study looked at caloric restriction — not fasting. Now other studies have shown that fasting can confer all of the same benefits to health and longevity that calorie restriction does, but fasting was not examined in this study.
Earlier research had already shown that while rodents that got exercise lived longer than those that did not, it was the average lifespan that was longer, not the maximum age at death. So exercise helped prevent early death in some percentage of animals, but did nothing to extend the lifespan beyond the normal.
Comparing calorie restricted animals to those that got lots of exercise, the calorie restricted animals lived longer, exceeding the ‘normal’ average lifespan for the species. The purpose of this latest study was to see if they could find the reason behind these earlier results.
In the newly reported study, mice that ate as much as they wanted and got little exercise had the highest levels of insulin-like growth factor (IGF-1), while both exercise and calorie restriction lowered that. Insulin itself was high in both animals that ate freely and those that ate freely and exercised. Both exercise and caloric restriction lowered 8-hydroxyguanosine (8-OHdG) levels, the presence of which is indicative of DNA damage. In summary, only insulin levels were clearly associated with the longer life expectancy, though researchers are not suggesting that insulin alone was responsible for the difference.
The authors suggest that reducing calories produces beneficial changes in ‘hormone levels’ without being too specific about which hormones. The analysis goes on to say:
A handful of studies comparing calorie restricted people to people who are avid exercisers, found similar hormonal benefits among those eating less. However, calorie restriction studies are difficult to carry out in people because participants often complain of feeling hungry, lethargic, and cold.
Well yes, calorie restriction is difficult for humans. Why not study intermittent fasting instead? A properly scheduled intermittent fast without caloric restrictions is very easy to follow. Intermittent fasting with mildly restricted calories is also easier than the typical caloric restriction diet — which has people eating all the time, but too little food to ever be satisfied. Better a small eating window daily, and fasting the rest of the time. You can eat one satisfying meal, at least, which makes the entire process more tolerable. Finding enough randomly selected individuals for prolonged caloric restriction studies will be nearly impossible — the drop-out rate will skew any data collected. Intermittent fasting without calorie restriction is so easy, however, that a large study could be undertaken with no more difficulty than in any other human-based studies that require modified behavior.
