Supplements categorized as “thermogenic” include any compounds that help boost your metabolism. This can result in burning additional calories regardless of your activity level. While some thermogenics cause nervousness, insomnia and gastrointestinal problems, the others are safe when used in moderation and in accordance with your doctor’s recommendations.
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You might only think of it as your morning pick-me-up, but caffeine also offers thermogenic properties. According to a 2007 publication by the American Physiological Society, one theory of how caffeine works is that it may alter fat and carbohydrate metabolism. Caffeine is readily available for use in coffee, tea, soda and many energy drinks. You can also find caffeine in pill and powder forms. The average cup of coffee contains 100 milligrams of caffeine, while energy drinks may contain upwards of 200 milligrams per serving. Experts report that headaches and other side effects are common after 400 milligrams of caffeine -- so you may want to limit your caffeine intake to 2 or 3 cups of coffee per day. If you're pregnant, nursing or have a medical condition, check with your doctor about how much caffeine, if any, is right for you.
Many types of green tea products contain caffeine, but even caffeine-free versions boast thermogenic qualities, possibly as a result of catechins -- antioxidants in green tea that may increase energy expenditure. According to a 1999 study in the American Journal of Clinical Nutrition, green tea extract influences thermogenesis beyond caffeine alone. If you experience caffeine sensitivity, a caffeine-free green tea extract may provide the fat-burning benefits of thermogenesis without the side effects of stimulants. Drink 2 to 3 cups of green tea per day, or talk to your doctor about taking green tea extract.
Cayenne adds fiery flavor to your meals, and capsaicin -- the active compound in the peppers -- may help you burn fat by increasing your metabolism. A 2007 article in the American Journal of Physiology states that capsaicin may increase energy expenditure immediately after a meal containing it. You can add cayenne pepper directly to food or brew tea with it. If the taste is too much for you, you may prefer cayenne pepper extract in capsule form. Capsaicin can cause heartburn and stomach discomfort, so start with small amounts to test your sensitivity.
Herbal Fat Burners
The supplement market is flooded with fat burners and other combination thermogenic products that contain multiple ingredients aimed at weight loss. While many of these supplements include the above compounds, they also contain herbal extracts known to be dangerous to your health. Many of these "natural fat burners" boast extreme thermogenic properties, making them popular ingredients in many commercial weight-loss supplements; however, these additives are rarely regulated. Bitter orange, which is used in some herbal thermogenic supplements, contains a powerful stimulant called synephrine that has been associated with agitation, headaches, heart palpitations and hypertension. Long-term side effects of fat burners containing bitter orange and similar herbal extracts include kidney damage, heart attack, stroke and even death, according to NYU Langone Medical Center. When looking for a thermogenic, safety should be paramount -- consult your doctor before using any supplement as product labels can be misleading.