Insects hold clues for human obesity

The metabolism of caterpillars evolved based on diet, Behmer and his team found.

Ever seen a fat insect? Probably not. Spencer Behmer may have the answer why, and that could have implications for what is billed as the current human obesity epidemic.

Behmer, an entomologist with the Texas Agricultural Experiment Station, and several other researchers conducted a series of experiments to find out whether caterpillars could adapt to extreme changes in their nutritional environment.

By manipulating the nutritional environment of diamondback moth caterpillars, the researchers found that the insects evolved different physiological mechanisms related to fat metabolism. Which mechanism was used depended on whether the caterpillars were given carbohydrate-rich or carbohydrate-poor food.

The team's work was published recently in the Proceedings of the National Academy of Sciences.

Metabolisms adjust to extreme environments

The researchers theorized that caterpillars—and animals in general—can evolve metabolically to adjust to extreme nutritional environments.

All animals need carbohydrates for energy and protein to build muscle and tissue, Behmer said. Different animals, however, need different amounts of these two macronutrients and sometimes it can be literally feast or famine for one or both of them.

"It's difficult to find in any environment a nutritionally perfect food," he said.

The researchers studied the insects over eight generations. In one experiment they fed caterpillars artificial diets that were rich in protein and low in carbohydrates (an Atkins-like diet); at other times the caterpillars received diets low in protein and high in carbohydrates (a high-carbohydrate diet).

In a second experiment caterpillars were allowed to freely eat one of two plants, an Arabidopsis mutant low in starch or an Arabidopsis mutant (plant) high in starch.

full story...