Dr. Oz’s Not-So-Amazing “Fat Busters”

Joe Schwarcz, Ph.D.
December 18, 2012

Miracles are pretty rare events. Except on television’s “Dr. Oz Show,” where they appear frequently. Oz doesn’t claim to raise the dead or part the Red Sea, but he does raise people’s hopes of parting with their flab. And he’s certainly not shy about flinging about the word “miracle.” Oz and his producers do not pull miracles out of an entirely empty hat. They generally throw in some stunted facts that get nurtured into pretty tall tales. I have also noticed that Oz’s miracles are not long-lasting. Raspberry ketones, acai berries and African mango, once hyped as amazing “fat busters,” have given way to chlorogenic acid and Garcinia cambogia.

Coffee Bean Hype

Chlorogenic acid perked the public’s interest when the great Oz introduced green coffee bean extract as the next diet sensation. Its name is derived from the Greek “chloro” for pale green and “genic,” which means “give rise to.” (Chlorine itself is a pale green gas.) “Chlorogenic acid” is not a single compound, but a family of closely related compounds found in green plants, which, perhaps surprisingly, contain no chlorine atoms.

Perhaps having forgotten about his previous weight-control miracles, Oz introduced coffee bean extract as an “unprecedented” breakthrough based on a study by Dr. Joe Vinson , a respected chemist at the University of Scranton who has a long-standing interest in antioxidants, including chlorogenic acid.  Because chlorogenic acid had been shown to influence glucose and fat metabolism in mice, Vinson speculated that it might affect humans as well. Since chlorogenic acid content is reduced by roasting, a green bean extract was chosen for the study.

Collaborating with colleagues in India who had access to volunteers, Vinson designed a trial whereby overweight subjects were given, in random order, for periods of six weeks each, either a daily dose of 1,050 mg of green coffee bean extract, a lower dosage of 700 mg, or a placebo [1]. Between each six-week phase there was a two-week “washout” period during which the participants took no supplements. There was no dietary intervention; the average daily calorie intake was about 2,400. Participants burned roughly 400 calories a day with exercise. On average there was a loss of about a third of a kilogram per week. Interesting, but hardly “staggering.” And there are caveats galore.

The study involved only eight men and eight women, which amounts to a statistically weak sample. Diet was self-reported, a notoriously unreliable method. The subjects were not really blinded since the high dose regimen involved three pills, and the lower dose only two. The results have other curious features. In the group that took placebo for the first six weeks, there was an 8-kilogram weight loss during the placebo and washout phase, but almost no further loss during the high-dose and low-dose phases. But the time that critics reacted to Oz’s glowing account, overweight people were already panting their way to the health food store to pick up some green coffee bean extract that might or might not contain the amount of chlorogenic acid declared on the label. As for Oz, he soon moved on to his next “revolutionary” product, Garcinia cambogia, unabashedly describing it as the “Holy Grail” of weight loss.

Garcinia Hype

In a recent segment [2], Oz and guest Julie Chen, M.D., demonstrated with a plastic contraption with a balloon inside that was supposed to represent the liver. A white liquid, supposedly a sugar solution, was poured in, causing the balloon, representing a fat cell, to swell. Then a valve was closed, and as more liquid was introduced, it went into a different chamber marked “energy.” The valve was said to represent how Garcinia extract prevents the buildup of fat in fat cells. While playing with balloons and a plastic liver may make for entertaining television, it makes for pretty skimpy science.

Contrary to Oz’s introduction that “you are hearing it here first,” there was nothing new about Garcinia. There’s no breakthrough, no fresh research, no “revolutionary” discovery. In the weight-control field, Garcinia cambogia is old news. Extracts of the rind of this small pumpkin-shaped Asian fruit have long been used in “natural weight loss supplements” Why? Because in theory, they could have an effect.

The rind of the fruit, sometimes called a tamarind, is rich in hydroxycitric acid (HCA), a substance with biological activity that might be relevant to weight loss. Laboratory experiments indicate that HCA can interfere with an enzyme that plays a role in converting excess sugar into fat, as well as with enzymes that break down complex carbohydrates to simple sugars that are readily absorbed. Furthermore, there are suggestions that Garcinia extract stimulates serotonin release that can lead to appetite suppression.

Laboratory results that point toward possible weight loss don’t mean much until they are confirmed by proper human trials. And there have been some. Fifteen years ago, a randomized trial involving 135 subjects who took either a placebo or a Garcinia extract equivalent to 1500 mg of HCA a day for three months, showed no difference in weight loss between the groups [3]. A more recent trial involving 86 overweight people who took either two grams of extract or placebo for ten weeks echoed those results [4]. In-between these two major studies there were several others [5], some of which did show a weight loss of about one kilogram over a couple of months, but these either had few subjects or lacked a control group. Basically, it is clear that if there is any weight loss attributed to Garcinia cambogia, it is virtually insignificant. But there may be something else attributable to the supplement, namely kidney problems {6]. Although incidence is rare, even one is an excess when the chance of a benefit is so small. So Garcia cambogia, like green coffee bean extract, can hardly be called a miracle. But it seems Dr. Oz puts his facts on a diet when fattening up his television ratings.

  1. Joe Vinson. Randomized,double-blind, placebo-controlled, linear dose, crossover study to evaluate the efficacy and safety of a green coffee bean extract in overweight subjects. Diabetes, Metabolic Syndrome and Obesity 5:21-27, 2012.
  2. Garcinia cambogia: The newest, fastest fat-buster, Dr. Oz Show, Oct, 2012.
  3. Heymsfield SB and others. Garcinia cambogia (hydroxycitric acid) as potential antiobesity agent: A randomized controlled trial, Vol. 280, 1998.
  4. Ji-Eun Kim J-E and others. Does Glycine max leaves or Garcinia cambogia promote weight-loss or lower plasma cholesterol in overweight individuals: a randomized controlled trial. Nutrition Journal 10:94, 2011.
  5. Igho Onakpoya I and others. 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 doi: 10.1155/2011/509038, 2011.
  6. Li JW, Bordelon P. Hydroxycitric acid dietary supplement-related herbal nephropathy. American Journal of Medicine 124(11):e5-6, 2011.

Dr. Schwarcz is director of McGill University’s Office for Chemistry and Society. In addition to teaching chemistry at McGill, he hosts a weekly “phone-in” show about chemistry on Montreal radio station CJAD (Sundays from 3 to 4 PM) and writes a weekly column called “The Right Chemistry” in the Montreal Gazette, and has a regular TV feature entitled “Joe’s Chemistry Set” on the Canadian Discovery Channel. His books Radar, Hula Hoops and Playful Pigs and The Genie in the Bottle feature commentaries on the fascinating chemistry of everyday life.

This article was posted on December 18, 2012.