Does Green Tea Burn Body Fat?

Green tea is an astringent, bitter-tasting beverage that contains a mixture of various chemicals such as flavonoids and caffeine, but very few of the fundamental nutrients necessary for living organisms. Camellia sinensis, the plant from which it is derived, originated in China, but green tea has become popular throughout the world. Unlike similar drinks such as white tea, black tea and oolong, green tea is not fermented before it is steamed and dried. This process leaves most of the ingredients intact. People have attributed many health benefits to green tea, not all of which are substantiated. However, research suggests that green tea does harbor certain weight loss properties.

Fat Oxidation

Green tea does not just induce weight loss by creating a calorie deficit, which is simply a matter of lowering your calorie intake. Rather, green tea is believed to have the effect of increasing your metabolic rate and the oxidation of fat. Oxidation is formally defined as a change in the oxidative number of a molecule, but it's easier if you consider it in more concrete terms. One example is cellular respiration, the process by which your body converts molecules such as sugars and fatty acids into ATP, a compound that acts to transfer energy as a kind of molecular currency. The energy that the body liberates from ATP powers reactions such as muscle contractions. When people talk about green tea as an engine of weight loss, they are actually talking about the rate at which this phenomenon occurs.

Catechins

Catechin --- a molecule also found in red wine, chocolate and certain fruits --- is supposed to be the engine that drives the increase in the rate of metabolism. It's an antioxidant, or a molecule that inhibits the production of dangerous free radicals that damage cells during the oxidative process. The study of green tea focuses on the health benefits of catechins.

Weight Loss

An often-cited 2005 study published in "The American Journal of Clinical Nutrition" by a group of Japanese researchers found that the daily consumption of tea containing 690 mg of catechins for 12 weeks brought a "significant" reduction in several measurements of fat, including body mass index, waist circumference and body fat mass. However, a more recent study from 2010 concluded that the clinical significance of these reductions is "modest at best." Further studies will illuminate the precise role of catechins as a vehicle for weight loss. For now green tea appears to be a good low calorie delivery source of catechins, but it is just one part of an overall healthy diet.

Metabolic Rate

Green tea appears to increase the 24-hour energy expenditure --- the amount of calories burned in a single day --- by about 4 percent. It may also have the ability to increase fat oxidation and thus thermoregulation --- which is the production of heat that results from the normal metabolic processes --- by as much as 17 percent, especially during moderate intensity exercise.

Metabolic Regulation

A 2008 study found that green tea extract can improve insulin sensitivity and glucose tolerance, at least in young men. Glucose is a form of sugar that acts as the main source of energy for the body. Insulin is a hormone that ushers the sugar into cells when blood glucose levels rise to a certain level. Insulin sensitivity is good for the body since the hormone regulates both carbohydrates and the release of fat. Insulin resistance, on the other hand, is the condition known as diabetes, and it affects the body's energy use.