Just the feeling of being hungry can be enough to slow ageing and even the taste and smell of food can reverse the benefits of diet restrictions, according to a new study.
Previous studies have shown conclusively that restriction of calories can increase the life span of animals.
The new study, published on Thursday in the journal Science, found that hunger alone can increase life span in fruit flies.
Hunger induced in flies either by depriving them of amino acid molecules, or by stimulating brain areas linked to motivation to feed, extended their life span found researchers, including those from the University of Michigan in the US.
“We’ve sort of divorced [the life extending effects of diet restriction] from all of the nutritional manipulations of the diet that researchers had worked on for many years to say they’re not required,” said study co-author Scott Pletcher.
The study found that the perception of not having enough food is sufficient to cause the benefits of life extension.
The scientists induced hunger in flies in several ways.
In one method, they altered the amount of branched-chain amino acid molecules (BCAAs) in a test snack food, and then later allowed the flies to freely feed on a buffet of yeast or sugar food.
Scientists found the flies that fed on the low-BCAA snack consumed more yeast than sugar in the buffet than those fed the high-BCAA snack.
The preference for yeast over sugar is an indicator of need-based hunger, researchers explained.
This behavior was not due to the calorie content of the low-BCAA snack as the flies consumed more food and more total calories.
Researchers also found when the flies ate a low-BCAA diet for life, they lived significantly longer than those fed high-BCAA diets.
Scientists then activated nerve cells associated with the hunger drive in flies, using exposure to red light.
Flies treated this way were found to consume twice as much food than those not exposed to the light stimulus.
These flies also lived significantly longer than flies used as a control.
“We think we’ve created a type of insatiable hunger in flies. And by doing so, the flies lived longer,” study co-author Kristy Weaver said.
While scientists only used flies to conduct the study, they said “there’s every reason to expect that the mechanisms discovered are likely to modulate hunger drives in other species”.
“Demonstration of the sufficiency of hunger to extend life span reveals that motivational states alone can be deterministic drivers of aging,” researchers concluded in the study.
