Insects can adjust their metabolism and behavior to their food

Sep 22, 2006 10:38 GMT  ·  By

Recently, Dr. Spencer Behmer - an entomologist with the Texas Agricultural Experiment Station - and his team studied how caterpillars adapt to extreme changes in their nutrition. The study might have implications on the research of human obesity epidemic.

Changing the food quality of diamondback moth caterpillars (photo), scientists discovered different metabolic mechanisms related to fat, depending on the amount of sugars on their food.

The study was published in the Proceedings of the National Academy of Science.

Caterpillars - and animals in general - can adjust metabolically and by behavior to their food environment. "All animals need carbohydrates for energy and protein to build muscle and tissue", Behmer said. Every species has its nutrients amount necessities and sometimes there can be shortage or excess of both. "It's difficult to find in any environment a nutritionally perfect food," he said.

In one experiment, the team fed caterpillars with artificial diets: rich in protein and low in carbohydrates (an Atkins-like diet), low in protein and high in carbohydrates (a high-carbohydrate diet).

In a second experiment caterpillars were free to eat mutant plants of Arabidopsis poor in starch or rich in starch. "When the caterpillars were reared in carbohydrate-rich environments for multiple generations, they developed the ability to eat excess carbohydrate without adding fat to their bodies", Behmer said. "On the other hand, those reared in carbohydrate-poor environments showed an ability to store ingested carbohydrates as fat".

"Also after multiple generations on the low-starch plants, female moths preferred to lay their eggs on these same plants. This, Behmer said, is one of the first instances of a moth showing egg-laying behavior that is tied to a plant's nutritional chemistry".

"Moths from low-starch plants might avoid the high-starch plants because these plants might make their offspring obese, he explained. Female moths reared on the high-starch mutant for multiple generations showed no preference for either mutant plant."

"Inferences can be made to humans from this work, he said. Looking back over human history, even as recently as 100 years ago, the diets of western cultures have undergone some radical changes."

Human nutrition asks for the same nutrients. "But, Behmer said, humans are not well adapted to diets containing extremely high levels of carbohydrates."

"Historically we haven't always had a lot of access to carbohydrates," he said, "and one of the biggest sources of carbohydrate in our current food is refined sugar. Our bodies tend to convert most of this excess carbohydrate to fat."

The scientists blame the current human obesity epidemic on the lack of exercise.