Garcinia Cambogia for Fat Loss

Garcinia cambogia may promote fat loss, but scientific evidence is inconclusive.

Garcinia cambogia is a tropical fruit native to India and Southeast Asia. The fruit’s thick yellow rind supplies an active ingredient called hydroxycitric acid (HCA), which may help with weight loss through:

• Inhibitting lipogenesis. HCA is suggested to block ATP citrate lyase, an enzyme required for converting carbs into fatty acids.
• Increasing fat oxidation during exercise, potentially promoting healthy weight management.

Overview

Garcinia cambogia is a pumpkin-like fruit native to India and Southeast Asia that has historically been used as food and wellness herb. Among its many purported benefits, Garcinia cambogia is perhaps most popular for its inclusion in weight loss supplements thanks to its hydroxycitric acid (HCA) content.

HCA was first identified in 1969 as an inhibitor of the enzyme ATP citrate lyase, which is an essential to the the conversion of carbohydrates into fats.¹

The weight loss effects of HCA have been well documented in animal studies. Despite this, most human trials show that HCA found in Garcinia cambogia extract possesses limited and unreliable weight loss effects.

How Garcinia Cambogia May Help With Fat Loss

Block conversion of sugars into fats

According to numerous animal studies, HCA blocks the conversion of carbohydrates into fats, a process called de novo lipogenesis. HCA achieves this by inhibiting the enzyme known as adenosine triphosphate citrate lyase (ATP citrate lyase).² However, this process does not make a significant contribution to body fat in humans, which might explain why animal studies show far more impressive weight loss.

Potential decrease of appetite

Several animal and test tube studies have shown that the HCA content of Garcinia cambogia helps increase serotonin levels, which is a brain chemical responsible for regulating eating behavior and appetite. ³Other studies show that Garcinia cambogia extract also displayed activities similar to leptin, which is known as the “satiety hormone” because it helps inhibit hunger.⁴

Despite this, thus far human studies have failed to reproduce these appetite-suppressing activities. As such, they remain largely theoretical and may be restricted to animals.⁵

Garcinia Cambogia’s Fat Loss Reputation

Garcinia cambogia is a popular weight loss supplement ingredient. Indeed, it was originally considered yet another miracle weight-loss drug promoted by Dr. Oz. However, it has failed to live up to the hype, since its weight loss effects are weak at best and non-existent at worst.

As one recent review paper summarizes, ” the evidence from RCTs [randomized controlled trials] suggests that Garcinia extracts/HCA generate weight loss on the short term. However, the magnitude of this effect is small, is no longer statistically significant when only rigorous RCTs are considered, and its clinical relevance seems questionable.”⁶

Research

Animal Research

Animal studies of garcinia cambogia extract and HCA as a weight loss agent were successful enough to inspire a large number of human trials.

Hydroxycitric acid may suppress fatty acid synthesis and food intake in male rats

In this study, researchers fed 24 male rats with a restrictive diet for 10 days, followed by a high-glucose diet supplemented with HCA for six days. Both respiration quotient and energy expenditure decreased during the first two days of supplementation, indicative of a decrease in fatty acid synthesis. HCA also suppressed food intake during the first three days.

• The researchers concluded that “These results indicate that, in this animal model, HCA suppresses de novo lipogenesis. Moreover, HCA may improve glucose tolerance” ⁹

Garcinia cambogia seems to reduce obesity in mice fed a high-fat diet

The researchers divided 36 obesity-prone male mice into three groups, with the first being fed a normal diet, the second a high-fat diet, and the third group a high-fat diet along with Garcinia cambogia extract.

At the end of the experiment, the third group had lower body weight gain, abdominal fat accumulation, and lipid and insulin levels than the other groups. Furthermore, the extract reversed adipose (fat) related genetic changes induced by a high-fat diet.

• The study concluded that “the Garcinia cambogia extract ameliorated HFD-induced obesity, probably by modulating multiple genes associated with adipogenesis” ¹⁰

Human Research

Unlike animal research, human trials of garcinia cambogia show mixed results. Even in the positive studies, the weight loss effect was relatively minor and has only been tested in the short-term.

Hydroxycitric acid (1500 mg)  does not appear to promote weight loss in overweight individuals

In this influential, randomized, double-blind trial, 135 overweight people took either HCA (1500 mg) or placebo daily for 12 weeks while following a high-fiber, low-energy diet. Although both groups lost weight by the end of the study, there was no significant difference between them.

• The researchers concluded that “Garcinia cambogia failed to produce significant weight loss and fat mass loss beyond that observed with placebo“¹¹

Hydroxycitric acid (3 g) does not appear to enhance metabolism in men with or without exercise

This randomized, double-blind, crossover study tested the hypothesis that HCA might promote weight loss by affecting energy expenditure (EE) and fat oxidation in 10 men. The men were  given placebo or HCA (3 g) daily for 3 days, and had their EE and fat oxidation tested with or without 45 min of aerobic exercise. The study found no significant differences between placebo or HCA in either case.

• The researchers concluded that “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“¹²

G cambogia extract (1000 mg HCA) appears to reduce body fat

In this randomized, double-blind study, 44 people were treated with Garcinia cambogia extract (1000 mg HCA) or placebo daily for 12 weeks. At the end of the study, the Garcinia group saw significant reductions in body fat compared to placebo.

• The researchers concluded that “G cambogia reduced abdominal fat accumulation in subjects, regardless of sex, who had the visceral fat accumulation type of obesity“¹³

Hydroxycitric acid (4667 mg) appears to induce weight loss, especially when combined with niacin-bound chromium and gymnema sylvestre extract

For this randomized, double-blind clinical trial, 60 moderately obese subjects were divided into three groups. The first was given hydroxycitric acid (HCA 4667 mg) before meals, the second was given HCA (4667 mg) plus niacin-bound chromium (NBC) and gymnema sylvestre extract (GSE), while the third group received placebo.

After eight weeks of treatment, both HCA groups had a significant reduction in body weight, BMI, food intake, total cholesterol, low-density lipoproteins, triglycerides, and serum leptin levels compared to the 3rd group. However, the effects were more pronounced among the second group participants.

• The researchers concluded that “optimal doses of HCA-SX and, to a greater degree, the combination of HCA-SX, NBC, and GSE can serve as an effective and safe weight loss formula that can facilitate a reduction in excess body weight and BMI, while promoting healthy blood lipid levels” ¹⁴

Hydroxycitric acid (500 mg) may increase fat usage during moderate intensity workouts

In this double-blind trial, six untrained men were given 500 mg of HCA or a placebo for five days and underwent moderate endurance exercise. The results showed an increase in the free fatty acid concentrations in the bloodstream, as well as a decrease in respiratory exchange ratio, indicating an increase in fat oxidation and sparing of carbohydrates as an energy source.

• The authors of the study concluded that “short-term ingestion of HCA increases fat oxidation during moderate intensity exercise also in untrained men” ¹⁵

Dosage For Fat Burning

• Clinical trials have used very different doses — as low as 500 mg and as high as 4667 mg of HCA
• Most commercial supplements provide anywhere from 500 – 1400 mg Garcinia cambogia extract standardized to contain 60-80 % HCA

References