Tried and true

Several dietary supplements and natural substances have been studied for their fat-burning effects, including:

Green tea. Research has shown green tea supplements can promote modest weight loss-a few pounds in short-term studies of up to 12 weeks, when compared to placebo-and may help prevent weight regain. Catechins, one component of green tea, appear to have a variety of fat-burning effects, including increasing metabolism and the use of fat for fuel, and decreasing the rate at which body fat is created and stored. Green tea has a good track record of safe use.

Capsaicin. Capsaicin is the spicy-hot component of red chili peppers, and one randomized trial found that people lost twice the weight taking capsaicin compared with a placebo, over a 12-week period. The total effect was small, however: the capsaicin group lost about 2 pounds compared to a 1-pound loss in the placebo group. Capsaicin appears to increase metabolism, and supplements of up to 6 grams of capsaicin per day are considered safe and are well tolerated by most people.

L-carnitine. Our bodies make and use L-carnitine to transport fat within cells, so that the fat can be burned for energy. Studies support that L-carnitine supplements improve fat burning in the body, but clinical trials have yet to show a weight-loss benefit in obese people. L-carnitine may be useful for improving athletic performance, however, and up to 3 grams per day is considered safe.

New kids on the block

Raspberry ketones. When given to mice on a high-fat, high-calorie diet, raspberry ketones protected against excess weight gain and fat accumulation in the liver. Mice aren't people, however, so keep an eye out for future research, which should clarify what kind of effects raspberry ketones may have for weight-loss in people.

Bitter orange (Citrus aurantium). This product became more popular after the 2004 FDA ban on ephedra supplements. Bitter orange has effects similar to ephedra, including increasing metabolism, blood pressure, and heart rate, which can translate into weight loss. While bitter orange appears to be safe for short-term use-weeks, not months-in healthy adults, it also may have similar adverse effects as ephedra, so use it with caution if you have underlying health issues, such as heart disease, high blood pressure, or diabetes.

Thermogenics. Thermogenics refers to a broad category of substances that cause the body to produce heat through increased metabolism. Examples include fucoxanthin, a supplement derived from brown seaweed, and 7-KETO DHEA, a manufactured hormone that is related to, though not the same as, the naturally occurring human hormone DHEA. Even caffeine and green tea are considered to have some thermogenic action in the body. As with many fat-burning supplements, thermogenics can be safe for short-term use in healthy adults. However, if you have underlying health issues, such as heart disease, high blood pressure, or diabetes, you may need to steer clear of thermogenic weight-loss products.

Other ways to fight the fat

Fat burners may be worth a try, but if you have a pre-existing medical issue, such as diabetes, high cholesterol, kidney or liver disease, high blood pressure, or heart disease, check with your doctor before trying these products. And regardless of whether or not you add a fat burner to your weight management plan, there are many other steps you can take to kick start your metabolism and nudge the number on the scale in the desired direction.

Water. You may have heard it before, but it bears repeating: staying well hydrated can help with fat loss. Aim for 64 ounces of water per day and you'll likely feel better and may be less tempted to snack mindlessly. Other noncaloric options such as hot or iced tea or sparkling water count too.

Fiber. Fiber-from food and supplements-may be helpful to weight-loss efforts. Fiber will fill you up and has other health benefits too, such as lowering cholesterol. Focus on fiber-rich foods, such as whole grains and raw vegetables and fruit, and slowly add a fiber supplement, such as psyllium or inulin-a type of fiber which comes from chicory root-if desired. Don't forget the water, which your body needs to process the extra roughage.

Effective exercise. High-intensity interval training can burn lots of calories quickly. This kind of exercise involves going all out-so you're breathing hard enough that talking is difficult-for a short time, such as 30 to 60 seconds, followed by a minute or two of lower-intensity activity to recover. The cycle is repeated up to 10 times for a 20-minute workout. Alternate these workouts with regular physical activity throughout the week, and as your fitness improves, you can increase the high-intensity portion of the workout, and decrease the active rest period. If you aren't exercising regularly already, talk to your doctor before starting a high-intensity interval training workout plan.