A lot of nutrients, like pantethine, carnosine, and DHA, are known for their metabolism-boosting and anti-aging properties. Most nutrients have some beneficial effects on the body. But resveratrol may be at the top of the heap- it's a prime anti-aging compound with an extra fat-burning bonus! The pharmaceutical companies are cashing in, coming out with a multitude of supplements touted as weight-loss aids and anti-aging medicines.
Resveratrol works by activating a fat-blasting and anti-aging gene called SiRT1. It prevents weight gain on a high-fat diet and promotes weight loss on a calorie-restricted diet. It also improves endurance and stamina for exercise. It provides a variety of health benefits, not the least of which is improved cardiovascular health. 
Interest in resveratrol heightened when it was discovered to be a possible cause of the “French Paradox”, the seemingly unexplainable ability to live on a high-fat diet while having a lower rate of heart disease. Resveratrol helps the liver to metabolize fat and aids in the breakdown of stored fat.
Resveratrol is a polyphenol produced in blueberries and grapes as a defense mechanism against +Infectoloo and UV radiation. Grapes growing in a damp climate have more resveratrol than almost anything else- it's a strong antioxidant and antifungal! Resveratrol differs from grape seed extract because it's not a pterostilbene. These compounds are able to lower +Cholesterik and triglyceride levels, and they have anti-aging properties as well.
The amount of resveratrol in red wine can range from 2-14 mg. Dietary supplements are usually taken from the roots of a Japanese knotweed plant, a far cheaper source than grapes. Doses go from a few milligrams to 100 mg or more. Resveratrol is quickly absorbed by the body, reaching the bloodstream in less than thirty minutes. It's rapidly metabolized by the liver. 
Other than anecdotal reports, there's not much to go on besides a few cell studies, and some research is done on small animals- but the testing that has been done is very encouraging.