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“Natural” Weight-Loss Supplements: How Effective Are They?

Healthnotes Newswire (December 1, 2005)—Supplements containing bitter orange (Citrus aurantium) can increase the amount of calories burned in response to a meal, potentially leading to weight loss, according to Obesity Research (2005;13:1187–94); however, according to the American Journal of Medicine (2005;118:998–1003), many bitter orange supplements also contain other stimulants, such as caffeine, which may raise blood pressure when taken in combination.

About 50% of Americans are overweight or obese. Being overweight places an extra burden on the heart and other organs, increasing the chance of developing high blood pressure, stroke, gall bladder disease, diabetes, and heart attack.

The body burns calories in several different ways: by performing essential bodily functions, by metabolizing food, and through exercise. The resting energy expenditure refers to the amount of calories used to maintain the body’s basic metabolic functions, such as breathing, maintaining body temperature, and pumping blood. After a meal, the body burns extra calories in addition to those used during rest. This is called the thermic effect of food (TEF); reductions in the TEF are associated with weight gain.

The dried outer peel of bitter orange has been used historically to treat indigestion and diarrhea, and as a nervous-system tonic. The active components of the extract include synephrine and octopamine, whose chemical structures are similar to that of adrenaline. Interest in ephedra-free weight-loss aids has been growing since ephedra was banned for sale in the United States. Some dietary supplement manufacturers now promote bitter orange–containing formulas as a weight-loss aid, but few studies have actually assessed its usefulness and safety.

These two recent studies aimed to determine the value of bitter orange as a weight-loss supplement. In the first, 30 people’s resting energy expenditure was determined at the beginning of the study. They then ate a prepared meal, with 53% of calories from carbohydrates, 29% from protein, and 18% from fat. After the meal, TEF measurements were taken. Several days later, some of the people ate the test meal again, this time with the addition of a bitter orange supplement containing 26 mg of synephrine and 4 mg of octopamine. TEF measurements were then repeated. Heart rate and blood pressure were measured at regular intervals for five hours after taking the supplement.

Initially, TEF values were significantly lower in women than they were in men. When bitter orange was taken with the meal, TEF values of the women increased to levels comparable to those initially seen in the men, whereas addition of bitter orange did not affect TEF values in the men. There were no significant changes in blood pressure or heart rate with the bitter orange supplement. These results suggest that there are gender differences with respect to TEF, and that supplementing with bitter orange may increase TEF in women, possibly leading to weight loss.

In the second study, 10 adults (average age 27 years) were given either a single dose of a bitter orange supplement containing 47 mg of synephrine; a combination bitter orange supplement containing 5.5 mg of synephrine, 5.7 mg of octopamine, and 239 mg of caffeine; or placebo. All participants took each supplement, with one week between treatments. Heart rate and blood pressure were monitored for 12 hours after taking the supplements.

The combination supplement caused a significant rise in both systolic and diastolic (the top and bottom numbers in a blood pressure reading, respectively) blood pressures as compared with the placebo. Two hours after taking the supplement, systolic and diastolic blood pressures each rose more than 9 points above baseline values. The bitter orange–only supplement did not raise blood pressure; however, both supplements caused a temporary but significant rise in heart rate after six hours as compared with the placebo. From these results, it appears that bitter orange alone does not raise blood pressure, but when taken in combination with caffeine, significant blood pressure elevations may occur.

Bitter orange may be a useful adjunct to a comprehensive weight-loss program, but more studies are needed to confirm its safety and effectiveness.

Kimberly Beauchamp, ND, earned her bachelor’s degree from the University of Rhode Island and her Doctorate of Naturopathic Medicine from Bastyr University in Kenmore, WA. She cofounded South County Naturopaths in Wakefield, RI. Dr. Beauchamp practices as a birth doula and lectures on topics including whole-foods nutrition, detoxification, and women’s health.

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