A recent study by researchers from the University of Michigan in the US has found that fruit flies tricked into feeling hungry end up living longer even when they eat plenty of calories. The findings suggest that the perception of insatiable hunger alone can trigger the anti-aging effects of intermittent fasting. Intermittent fasting has become a popular diet fad in recent years, although at this point evidence supporting its benefits is limited and largely based on animal studies.
Work on fruit flies and rodents seems to suggest calorie restriction can extend lifespans and promote good health. To study the molecular mechanisms of fasting further, the researchers behind this latest investigation turned once again to the humble fruit fly. In the past, fruit fly studies have helped scientists identify numerous neural signals for hunger and satiety in the brain. These creatures share 75 percent of the same disease-related genes as humans, and their metabolisms and brains have useful similarities to those in mammals.
Branched-chain amino acids (BCAA) are essential nutrients that appear to trigger feelings of fullness in flies when consumed. Eating more BCAAs reduces their feelings of hunger. To explore how this might impact aging, researchers kept fruit flies hungry by giving them snacks low in BCAA. Their hunger was gauged by how much the insects ate from a buffet of food hours after consuming the snack.
Flies that were fed a low-BCAA snack ate more food at the later buffet. They also targeted protein-heavy foods over carbohydrate-heavy foods, a sign that the flies were driven by a need-based hunger, not a want-based one. When the team directly activated the neurons in fruit flies that trigger hunger responses, they found these hunger-stimulated flies also lived longer.
Researchers think chronic hunger might be an adaptive response, “mediated by modifications to histone proteins in discrete neural circuits, that slows aging.” The findings could help explain why low-BCAA diets seem to be good for our own health. It is possible that they provide the body with sufficient nutrients, while not quieting hunger signals in the brain completely.
However, the study’s authors caution that one study on fruit flies is not enough to draw a conclusion. They are interested in exploring whether the health of fruit flies is tied to eating for pleasure as well as for necessity. It is still early days, and far more research is needed before the results can be extended to humans – especially since some studies have produced conflicting results, or even highlighted potential dangers.