It is Never Too Late to Improve Health by Reducing Calorie Intake
Life lived on a comparatively high calorie diet is both shorter and less healthy than a life lived on a comparatively lower calorie diet, so long as one still obtains all of the necessary micronutrients needed to avoid malnutrition. This is clearly the case in near all species in which the outcome of calorie restriction has been assessed. Human trials of even modest calorie restriction have demonstrated a panoply of improvements to long term health. A great deal of overfeeding and calorie restriction research is conducted in short-lived species, however, such as the study here in flies. The principle remains the same, though: it is never too late to try a lower intake of calories as a lifestyle choice intended to improve health.
Many animal studies have shown that eating less - meaning sharply restricting calories without malnutrition - lengthens lifespan. While human trials have shown evidence of beneficial effects of eating less on health, especially in healthy obese individuals, studies examining effects on lifespan have been unrealistic for humans.
Fruit flies live short and fast - the lifespan of flies raised on a high calorie diet is less than 80 days, while the longest lived on a low calorie diet can reach 120 days. In this study, researchers looked specifically at male flies. Young flies switched from a high calorie to a low-calorie diet at 20 days old lived very long lives, similar to the flies fed a low-calorie diet from day one. What surprised the researchers was that switching the flies' diet to a low calorie one remained a reliable way to extend lifespan even for old flies in ill health. The older insects raised on the high calorie diet had more lipids in their bodies, and they expended more energy defending their bodies from reactive oxygen species. They also had a higher death rate than flies raised on the low-calorie diet. But when the surviving high calorie flies were switched to a low-calorie diet at 50 or even 60 days (when most of the high calorie flies had already died) their metabolisms changed, their death rate plummeted, and their lifespans lengthened.
The team's results show that flies' metabolisms can adapt to a change in diet even in old age. Since many basic metabolic pathways in fruit flies are shared with humans, this study suggests that human metabolism may respond the same way, and individuals eating a high calorie diet could benefit from reducing their calorie intake at old age. The researchers are currently analyzing data from female fruit flies to see if there are any sex-related differences in response to diet shifting.
Link: https://today.uconn.edu/2023/12/fat-flies-live-longer-on-a-diet-at-any-age/