It Helps You Lose Weight

By intermittent fasting or simply reducing what you eat, you can cut calories by 30%, be healthy and live a long life. Calorie restriction and fasting can increase life by 40% or more in some species. When you limit calories, the body engages in a defense mechanism that helps it survive the problems it encounters.
Resveratrol may help you lose weight by mimicking the health effects of fasting or calorie reduction. It does this by stimulating the formation of adiponectin, the same hormone that increases in individuals who practice calorie restriction. [1]

Adiponectin promotes metabolic and cardiovascular health through weight loss, lipid metabolism and regulation of blood sugar levels.
In other words, adiponectin helps maintain normal blood sugar, helps your heart, and helps you lose weight. Since Resveratrol stimulates adiponectin, you benefit from both.

[1] Renes J, et al. Calorie restriction-induced changes in the secretome of human adipocytes, comparison with resveratrol-induced secretome effects. Biochim Biophys Acta. 2014 Sep;1844(9):1511–1522.