Green tea (aka Camellia sinensis) has a modest effect on weight loss, usually attributed to a mix of caffeine and catechins. While Shilstone favors green tea as an antioxidant, there is "some research demonstrating it has thermogenic properties," which means it produces heat to burn calories. In one study in the American Journal of Clinical Nutrition, participants taking an extract with high catechin content upped energy expenditure by 4 percent over 24 hours.
Cautions: People with sensitivity to caffeine should monitor their green tea intake. Symptoms to watch for include increased restlessness, insomnia, and anxiety.
Dosage: For weight control, the American Botanical Council Clinical Guide to Herbs recommends two 250 mg capsules of green tea extract three times daily with meals.
With guarana seeds boasting twice the caffeine of coffee beans, it's easy to see how this supplement built its reputation as a metabolism booster. Blumenthal calls guarana's flavor "unique to itself, not too bitter and relatively pleasant," which makes it a natural in bottled, flavored drinks, or mixed with green tea or yerba mate.
Cautions: Anyone who's caffeine-sensitive should consult their physician, as should those with high blood pressure or heart trouble.
Dosage: A standard dose is 250 mg per day. Guarana is often found in formulas with other ingredients; in these instances, "look for no more than1,000 milligrams of guarana," says Fleischmann.
Hydroxycitric acid is derived from Garcinia cambogia, an Indian fruit. Animal research indicates HCA suppresses appetite and reduces calories stored as fat, but human studies are unclear. In a 12-week trial of 89 overweight women, those taking HCA lost 3 pounds more than the placebo group, but other studies found no difference.
Cautions: Fleischmann says he knows of no side effects or complications from taking HCA. "It has of safe use," he a number of years says.
Dosage:"From 750 to 1,000 milligrams a day is a good recommendation as part of a formula," advises Fleischmann.
The caffeine in this plant-derived beverage from South America compares to tea. A study of 47 overweight subjects taking yerba mate with guarana and damiana for 45 days saw an average weight loss of 11 pounds vs. less than a pound in the placebo group; the former felt full faster, and maintenance resulted in no weight regain.
Cautions: Caffeine-related side effects include restlessness and increased high blood pressure and heart rate. Drinking hot yerba mate may be linked to oral cancers, so drink the tea in moderation, and at a moderate temperature.
Dosage: Fleischmann suggests consuming yerba mate as a tea once a day, using 2 to 4 grams of unadulterated cut leaves per cup of hot