Question: We live in a day and age where obesity is at an all-time high. Whether it is due to fast food or due to the lack of time for exercise during the day, a staggering 77% of all Americans are trying to lose or maintain their current weight (Food Insight). To fight this issue, a lot of Americans looks for any “get skinny quick” scheme they can find. Weight loss supplement use is higher than it has ever been before. Many people claim that these supplements changed their lives and others claim that they had no effect whatsoever. My questions are do weight loss supplements work, and if so, how do they work?
Answer: A popular weight loss supplement is a supplemental Garcinia Cambogia extract. Garcina Cambogia contains hydroxycitrate acid (HCA), which is thought to be a weight reduction agent. HCA acts an inhibitor of a citrate cleavage enzyme, therefore inhibiting fatty acid synthesis (Lowenstein). A study conducted by Dr. John Lowenstein at the University Of Waltham Massachusetts found that liver fatty acid synthesis in rats is strongly inhibited by HCA. He found that a dose as little as 0.1 mmole/kg of body weight is sufficient enough to inhibit fatty acid synthesis by 25-30% in rats (Lowenstein). It is hypothosized that the mechanism of action by HCA reduces lipogenesis by reducing activity of lipogenic enzymes, like isocitrate dehydrogenase. It is also thought that HCA increases high-density lipoprotein levels, although both of these claims are not confirmed (Lowenstein). In a study conducted in 2002, HCA increased levels of the neurotransmitter serotonin in the brains of rats. This neurotransmitter is involved in appetite control and regulation of eating behavior (Ohia et al.). However, other studies show that the results are not as substantial in humans. Dr. Igho Onakpoya and other researchers completed a systematic review of randomized clinical trials (RCTs) involving Garcinia Cambogia Extract containing HCA. Dr. The review looked at 12 RCTs in total, examining studies that were randomized, double blind and placebo-controlled. All of the subjects were overweight or obese, and gender or race did not play a factor. Three trials all showed a significant loss in total body fat in the HCA group compared to the placebo. Moreover, in two of those studies, visceral and subcutaneous fat levels significantly decreased as well. However, 9 of the trials did not show a significant difference in body fat loss between a placebo and HCA (Onakpoya et al.). In addition to no significant weight lost, many of the subject reported adverse events from their treatment with HCA, such as headache or gastrointestinal (GI) symptoms. In fact, in one trial, GI symptoms were twice as frequent in the HCA group compared to the placebo. Garcina Cambogia extracts may help subjects lose weight, short term. However, according to these RCT, the size of its intended effect is very small and not statistically significant (Onakpoya et al.). A big thing to remember about weight loss supplements is that they do not require approval from the FDA, like all pharmaceutical drugs do. This is a huge reason why there is so much conflict, debate, and confusion about these supplements. When it comes down to it, the best option for losing weight is simply a healthy diet and exercise.
Figure 1: Effect of dosage of HCA on body weight. The dosages from included RCTs did not produce a linear effect on body weight (Onakpoya et al.)
- Scott I.
“Americans Concerned About Their Weight”. Food Insight. (2014).
Lowenstein, John. “Effect of ( -)-Hydroxycitrate on Fatty Acid Synthesis by Rat Liver in Vivo*”. The Journal of Biological Chemistry, 246, 629-632. (1971).
Ohia, S., Opere C., LeDay, A., Bagchi, M., Bagchi, D., & Stohs, S. “Safety and mechanism of appetite suppression by a novel hydroxycitric acid extract (HCA-SX)”. Molecular and Cellular Biochemistry, 238(1-2), 89-103. (2002).
Onakpoya, I., Hung, S., Perry, R., Wider, B., & Ernst, E. “The Use of Garcinia Extract (Hydroxycitric Acid) as a Weight loss Supplement: A Systematic Review and Meta-Analysis of Randomised Clinical Trials”. Journal of Obesity, Vol. 2011, 1-9. (2010).