I happened to watch a recent episode of Dr Oz, something I don’t typically do. But, when I was flipping through the channels I saw that Dr Oz was going to be talking about some new breakthrough weight loss supplement which obviously got my attention. He was also going to discuss natural ways to relieve bloating. Both topics sounded interesting and I had a bit of free time, so I decided to watch it.

First, HERE is the segment about the supplement,which is green coffee bean extract (GCE). Did you watch it? This will all make more sense if you do. It is clear that Dr Oz agrees that this supplement is amazing. He states that he was skeptical. So what did he do to help confirm the benefits of the supplement? Did he actually read the available research on the subject? From what he agreed to and what he said on the show we can assume he did NOT. Instead he gives the supplement to 2 viewers so they could take it for 5 days to see if they would lose weight. Really!? WTF! Is he serious about this type of testing? Apparently he is. The two viewers did lose weight, 2 and 6 lbs. That’s great, but come on. That really does not tell us if the “supplement” actually did something on a physiological level or if it just made them modify their eating behavior so that they would lose weight. Basically, having the 2 viewers take the supplement for 5 days is a big waste of time! Dr. Oz should know better.

The guest on the show, Dr.Lindsey Duncan,  says a bunch of, how should I say this, ah… BULLSHIT! That sums it up well. Here are some statements by Dr.Duncan; (some paraphrased)

  • “each participant lost 17lbs in 12 weeks”
  • “lost 10% of body weight with no change in eating or activity”
  • “sugar turns into fat”
  • “makes the body burn fat in the liver”
  • “take 800 mg 2 times a day”
  • “roasting coffee beans removes the chlorogenic acid, so coffee does not contain this compound”

These are apparently the important aspects about what the supplement does, how it works and how much to take. Really! Well, I guess it is time to look at this study as it seems to be the impetus for all the hubbub.

The paper is freely available, click HERE if you would like to read it, attention Dr Oz, I am referring to you as well.

Vinson, J et al (2012). 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 Metab Syndr Obes; 5: 21–27.

Overall, I think this was a decent study. However, there are two very important limitations to it. First, there where only 16 total participants. Second, the dietary intake was NOT tightly regulated. Dietary intake was assessed through dietary recall, however the specifics of this aspect are not clearly stated in the paper. This is very important because dietary recall is well know to be a rather poor method of assessing true food/calorie intake. A nice 8 to 12 week, metabolic ward study with a few dozen, overweight and obese, male and female participants would go a long way in determining the true physiological benefit of this supplement. Until then we have to go with what we have.

There where 3 groups (treatment arms)

  • HD (high dose): 350 mg of GCA (green coffee extract) taken 3 x day, total of 1,050 mg/day
  • LD (low dose): 350 mg of GCA taken 2 x day, total of 700 mg/day
  • PL (placebo): 350 mg of a placebo taken 3 x day

Each arm was followed for 6 weeks.

Results (p.24) at the end of each arm (6 weeks each)

  • HD: average decrease of 4.48lbs, lose of x .75 lbs per week
  • LD: average decrease of 3.39lbs, lose of x .57 lbs per week
  • PL: no real change

Combining the HD and the LD arms resulted in a grand total of 7.87lbs lost during 12 weeks, which is a bit less than 5% of bodyweight. This averages to a decrease of .66 lbs per week. Not bad. In fact, I would say the results were pretty damn good for just taking a relatively safe supplement.

Table 2 [pg 24]
Characteristics at start and end of each treatment arm for 16 preobese subjects
Characteristic HD arm P LD arm P PL arm P

M ± SD (95% CI)
M ± SD (95% CI)
M ± SD (95% CI)
M ± SD (95% CI)
M ± SD (95% CI)
M ± SD (95% CI)
Weight (kg) 72.86 ± 8.91 (68.11–77.61) 70.82 ± 8.40 (66.34–75.30) 0.002 71.25 ± 7.30 (67.36–75.14) 69.71 ± 7.30 (65.82–73.60) 0.003 72.15 ± 8.64 (67.55–76.75) 72.47 ± 8.47 (67.96–76.98) 0.353
BMI (kg/m2) 26.78 ± 1.55 (25.95–27.61) 26.03 ± 1.36 (25.31–26.75) 0.002 26.25 ± 1.37 (25.52–26.98) 25.66 ± 1.20 (25.02–26.30) 0.003 26.55 ± 1.96 (25.51–27.59) 26.67 ± 1.72 (25.75–27.59) 0.384
Percent body fat 25.94 ± 5.35 (23.09–28.79) 24.75 ± 5.20 (21.98–27.52) 0.001 25.94 ± 4.99 (23.28–28.60) 24.88 ± 4.99 (22.22–27.54) 0.002 25.88 ± 5.40 (23.00–28.76) 25.00 ± 5.52 (22.20–27.82) 0.014
HR (bpm) 76.94 ± 2.64 (75.53–78.35) 75.12 ± 3.63 (73.19–77.05) 0.031 74.62 ± 4.56 (72.19–77.05) 74.87 ± 4.50 (72.47–77.27) 0.752 76.19 ± 5.13 (73.46–78.92) 75.81 ± 4.10 (73.63–77.99) 0.549
SBP (mmHg) 129.12 ± 8.10 (124.80–133.44) 129.62 ± 6.74 (126.03–133.21) 0.843 131.00 ± 6.93 (127.31–134.69) 128.25 ± 6.40 (124.84–131.66) 0.221 125.62 ± 6.90 (121.94–129.30) 131.62 ± 9.33 (126.65–136.59) 0.031
DBP (mmHg) 81.75 ± 3.00 (80.15–83.35) 81.62 ± 3.28 (79.87–83.37) 0.926 81.62 ± 9.24 (76.70–86.54) 83.00 ± 3.58 (81.09–84.91) 0.239 82.62 ± 2.39 (82.35–84.89) 83.50 ± 4.23 (81.25–85.75) 0.379
Abbreviations: CI, confidence interval; HD, high dose green coffee extract; LD, low dose green coffee extract; PL, placebo; BMI, body mass index; HR, heart rate; SBP, systolic blood pressure; DBP, diastolic blood pressure; M, mean; SD, standard deviation.

Based on the numbers above, how did the authors of the paper conclude “Significant reductions were observed in body weight (-8.04 +/- 2.31kg)” (p.21), which equates to 17.69 lbs? I am confused on how they got to this calculation. The numbers that are in the table and in the paper do not add up to their conclusion number.

Obviously this “17lb” number from the conclusion is the number Mr Duncan used. This number also equated with the “loss of 10% of bodyweight” statement which is actually shown in the Chart 1 on page 22 (the average weight  of the study participants was 169lbs). So Mr. Duncan did not make these numbers up per se, but based the data in the  paper they are not correct and way overstate the  results. Did Mr Duncan actually read the whole paper? It is actually relatively short, just a couple of pages contain the pertinent information, so 10 minutes of effort would have likely lead to a better understanding of the results (see my above calculations).

Why does he recommend 800 mg 2 x day, so 1,600 mg/day? Where did this amount come from. It certainly did NOT come from the above study as the HD arm used 1,050mg/day, which is the largest dose every used with humans, see below (Onakpoya et al).

Mr Duncan’s emphatic “Sugar turns into fat” statement really has nothing to do with this supplements ability to make you lose weight. Also, this statement is really NOT true. As much as I think a lower carb diet can be useful for weight loss for many people it is NOT because “sugar turns into fat” or that carbs, which causes an increase in insulin secretion, actually inhibits fat loss (Guyenet).

Finally, the supplement “increases fat use in the liver” may be true (Onakpoya et al), but is really meaningless unless there is some level of calorie deficit created through a decrease in intake and/or an increase in expenditure.

Before moving on to my conclusion, I want to highlight a few things from a recent review paper on green coffee extract as a weight loss supplement. Click HERE to read it. This paper was published in 2011, so it was likely available BEFORE the show. The authors only found 3 human studies that fit the quality criteria. These 3 studies were published in 2007, 2009,and 2006,which means they were all definitely available BEFORE the taping of the show. Therefore, they could have been reviewed by Dr Oz or his staff and Dr.Duncan.

From the abstract of the paper;

“The purpose of this paper is to assess the efficacy of green coffee extract (GCE) as a weight loss supplement, using data from human clinical trials…Five eligible trials were identified, and three of these were included. All studies were associated with a high risk of bias. The meta-analytic result reveals a significant difference in body weight in GCE compared with placebo (mean difference: − 2 . 4 7kg; 95%CI: − 4 . 2 3, − 0 . 7 2). The magnitude of the effect is moderate, and there is significant heterogeneity amongst the studies. It is concluded that the results from these trials are promising, but the studies are all of poor methodological quality. More rigorous trials are needed to assess the usefulness of GCE as a weight loss tool.”

From the 3 studies included, there was an average of .6lbs of weight loss per week from the use of the GCE supplement. Not bad. This amount is about the same as the results from the most recent study (Vinson et al) which was the one being referred to in the Dr Oz show. Interestingly, the dosages in these trials where only 180mg/day, 200mg/day,and 200mg/day,much less than the amounts used in the most current study.

Mr Duncan states that roasting coffee beans eliminated the chlorogenic acid (CGA), possibly one of the main chemicals found in coffee beans that can elicit the weight loss effects. However, the review paper by Onakpoya et al states “The daily intake of CGA in persons drinking coffee varies from .5 to 1 g” (p.1). From the current evidence, that range of intake would likely be enough to elicit the potential benefits from CGA. Therefore, from what I can tell Mr Duncan is wrong about the content of CGA in roasted coffee.

This supplement does seem promising for weight management. I am not shocked as Matt and I stated in our book that we thought caffeine and coffee were likely to be useful for weight management. So my problem is not with the use of this supplement, but with the unnecessary hype and lack of a critical view of it taken by Dr. Oz and his guest. Here is the conclusion, which I agree with, from the review paper on GCE;

 “The evidence from RCTs seems to indicate that the intake of GCE can promote weight loss. However, several caveats exist. The size of the effect is small, and the clinical relevance of this effect is uncertain. More rigorous trials with longer duration are needed to assess the efficacy and safety of GCE as a weight loss supplement.” (Onakpoya et al)

Why was this type of realistic view not presented on the show? Dr Oz has repeatedly misrepresented the facts on supplements, see Matts posts HERE,  HERE and HERE. What’s the deal Dr.Oz? I thought you were all about giving your audience and viewers the most up-to-date evidence-based information. Read these post for more on that topic, HERE and HERE.  To me, it looks like Dr Oz is selling out and that’s why I have lost a lot of respect for him.



Dr Oz Loses More Respect! Part 1 – Green Coffee Bean Extract