What's the connection between the red leaves of the fall and human obesity? Anthocyanins are red/purple/reddish pigments encountered in grape skins, blueberries, blackberries, purple corn, and other plant matters, but they give the reddened colors of the autumn leaves as well. Now, a team from Arkansas, led by Ronald L. Prior, points that anthocyanins could help in preventing obesity.

Still, tests made on animals show that consuming the whole fruit containing these pigments is a less effective method than eating an extract of the berry. Previous researches revealed that the anthocyanins prevented obesity in lab mice on a high-fat diet. The tested mice also presented healthful shifts in the levels of disease-related chemicals in their blood.
The new research, published in the ACS' Journal of Agricultural and Food Chemistry, pointed that mice feeding on a high-fat diet for 8 weeks and drinking water with purified anthocyanins from blueberries and strawberries were lighter and had less body fat than a control group.

"Anthocyanins fed as the whole blueberry did not prevent and may have actually increased obesity. However, feeding purified anthocyanins from blueberries or strawberries reduced obesity," wrote the authors.

Anthocyanins are found both in blue to red flowers, attracting pollinators, or blue to red fruits (like plums or apples), luring foraging animals. Some ornamental plant varieties have anthocyanins in their leaves, conferring them a color different from green (bluish or reddish).

These pigments also defend the plant against environmental stress and disease. There are hundreds of anthocyanin molecules in nature, all having slightly different chemical formulas.

Anthocyanins also have antioxidant properties, important in the fight against cancer, cardiovascular disease and age-related degeneration.

In autumn leaves, the anthocyanins have a protective role. Leaves change color in the fall when trees stop the photosynthesis while withdrawing their nutrients from the leaves to be stored into their roots. But the food withdrawal is not a rapid process and, in the meantime, leaves are left vulnerable to harmful light waves, and anthocyanins protect leaves by "shading" them from excessive sunlight during this relatively vulnerable period.