Clinical Briefs-With Comments from John La Puma, MD, FACP

(-)-Hydroxycitric Acid and Weight Loss

May 2000; Volume 3; 59

Source: Kriketos AD, et al. (-)-Hydroxycitric acid does not affect energy expenditure and substrate oxidation in adult males in a post-absorptive state. Int J Obes Relat Metab Disord 1999;23:867-873.

Available as an herbal supplement, (-)-Hydroxycitric acid [(-)-HCA] is promoted as a weight loss agent. It is hypothesized that (-)-HCA can increase fat oxidation by inhibiting citrate lyase, an enzyme that plays a crucial role in energy metabolism during de novo lipogenesis. The indirect inhibition of the cytosolic pool of citrate by (-)-HCA and the subsequent reduction in acetyl coenzyme A and oxaloacetate alter steps in the citric acid cycle that promote fat oxidation.

We hypothesized that supplementation with (-)-HCA would result in an increase in fat oxidation and metabolic rate, reflected by an increase in beta-hydroxybutyrate and energy expenditure (EE) and/or a decrease in respiratory quotient (RQ). Furthermore, during moderately intense exercise, we hypothesized that (-)-HCA supplementation would increase the rate of lactate conversion to glucose in the liver. No studies have investigated the effects of (-)-HCA supplementation in conjunction with a typical daily dietary composition (approximately 30-35% fat) on metabolic processes that could influence body weight regulation in humans.

Sedentary adult male subjects (n = 10, age 22-38 years, body mass index 22.4-37.6 kg/m2) were enrolled in a randomized, double-blind, placebo-controlled, crossover study involving three days of (-)-HCA (3.0 g/d) or placebo supplementation. Four laboratory visits were conducted: Protocol A with and without (-)-HCA treatment with no exercise; and Protocol B with and without (-)-HCA treatment with moderately intense exercise (30 min at 40% maximal aerobic fitness [VO2max] and 15 min at 60% VO2max). EE (by indirect calorimetry) and RQ were measured for 150 min following an overnight fast. Blood samples were collected for the determination of glucose, insulin, glucagon, lactate, and beta-hydroxybutyrate concentrations.

In a fasted state and following three days of (-)-HCA treatment, RQ was not significantly lowered during rest (Protocol A) nor during exercise (Protocol B) compared with the placebo treatment. Treatment with (-)-HCA did not affect EE, either during rest or during moderately intense exercise. Furthermore, the blood substrates measured were not significantly different between treatment groups under the fasting conditions of this study. These results do not support the hypothesis that (-)-HCA alters the short-term rate of fat oxidation in the fasting state during rest or moderate exercise, with doses likely to be achieved in humans while subjects maintain a typical Western diet.

COMMENT

These University of Colorado investigators add to the clinical work done on the enzyme HCA, in the rind of the fruit Garcinia cambogia, which might reduce how much fat the body actually makes. But according to this and most human evidence I’ve seen, it doesn’t work. The only human studies that support its use and show some weight loss combined 750 mg HCA with a low-calorie diet and exercise (a combination for the ages).

This well-designed, high-tech (they measured body composition by DEXA using a bone densitometer!) study notes that obesity is a chronic disease requiring lifestyle modification for a long-term solution. The authors also point out that the daily cost of 3 g/d of HCA approaches $40, and it’s not uncommon for people to waste their money in just this way.

Recommendation

Garcinia and HCA are not recommended for weight loss, short- or long-term. Refer patients to a medically sound weight management program for assistance with the skills needed to change their eating and fitness habits.