Fruit flies tricked into feeling hungry end up living longer even when they eat a lot of calories.
Findings from a recent study by researchers at the University of Michigan in the US suggest that the perception of insatiable hunger alone can trigger the anti-aging effects of intermittent fasting. The animal does not actually have to starve.
“We have divorced [the life extending effects of diet restriction] of all the nutritional manipulations of the diet that researchers have worked on for many years to say are not necessary,” says physiologist Scott Pletcher.
“The perception that there is not enough food is enough.”
Intermittent fasting has become a popular diet fad in recent years, although at this time the evidence supporting its benefits is limited and largely based on animal studies.
Work on fruit flies. (Drosophila melanogaster) and rodents seems to suggest caloric restriction can extend life expectancy and promote good health. But these are still early days, and much more research is needed before the results can be extended to humans.especially from some studies they have produced conflicting results, or even highlighted potential dangers.
To further study the molecular mechanisms of fasting, the researchers behind this latest research once again turned to the humble fruit fly.
In the past, studies of the fruit fly have helped scientists identify numerous neural signals of hunger and satiety in the brain. these creatures share 75 percent of the same disease-related genes that we do, and their metabolisms and brains they have useful similarities to those of mammals.
Branched-chain amino acids (BCAAs) are essential nutrients that appear to trigger feelings of satiety in flies when consumed. Eating more BCAAs therefore reduces the feeling of hunger.
To explore how this might affect aging, the researchers kept the fruit flies hungry by giving them low-BCAA snacks.
Their hunger was measured by how much the insects ate from a food buffet hours after consuming the snack.
Flies that were fed a low-BCAA snack ate more at the post-buffet. They also focused on protein-rich foods rather than carbohydrate-rich foods, a sign that the flies were driven by a hunger based on need, not desire.
So the researchers went straight to the source. When the team directly activated neurons in fruit flies that trigger hunger responses, they found that these hunger-stimulated flies also lived longer.
“Therefore,” Pletcher and colleagues write, “the motivational state of hunger itself, rather than the availability or energetic characteristics of the diet, might retard aging.”
Other experiments showed that reducing BCAAs in the flies’ diets also led their hunger neurons to create modified support proteins called histones, which bind to DNA and help regulate gene activity. The researchers believe that these modified histones could be the link between diet, hunger responses, and aging. Interestingly, previous studies have linked an increased supply of histones with an extended lifespan.
In light of the findings, the researchers believe that chronic hunger could be an adaptive response, “mediated by histone protein modifications in discrete neural circuits, that delays ageing.”
The findings could help explain why diets low in BCAAs appear to be good for our own health. Perhaps they provide the body with enough nutrients, without completely calming the hunger signals in the brain.
Of course, that idea needs a lot more testing. A study on fruit flies is not going to be enough.
For now, the researchers are interested in exploring whether the health of fruit flies is linked to eating for pleasure and for necessity.
The study was published in Science.