Irvingia gabonensis is the latest weight loss supplement to hit the marketplace, saturate the internet with advertisements, ignite forum discussions and flood my email inbox with questions. In the weight loss marketplace, this may gain the dubious distinction of becoming the next hoodia or acai berry (scam), but I'll just present the facts, make my case and then let you judge for yourself.
Irvingia gabonensis comes from a West African tree commonly known as the wild mango or bush mango. The trees bear edible fruits, and they're especially known for their nuts which go by many different names including ogbono, etima, odika or dika nuts. Like other nuts and seeds, Irvingia gabonensis is high in fat (50%), and oil can be extracted from them. Irvingia gabonensis is also comprised of 26.4% carbohydrate, 7.5% protein, 2.3% ash and 14% fiber. Dietary fibers are often recommended to aid with weight loss programs as well as for their health benefits.
The first Irvingia Gabonensis weight loss study: 2005
Due to its customary use in African cuisine and reputation as a health food, a research group based in Cameroon (Western Africa) set up a randomized double blind study in 2005 to see if Irvingia gabonensis could help with weight loss. 40 obese subjects, age 19 to 52, were divided into placebo and experimental groups. The experimental group received 1.05 grams of Irvingia seed extract 3 times a day (total 3.15 grams) for 30 days.
Subjects were examined weekly and tested for body weight, body fat and hip/waist circumferences. Blood pressure was measured and blood samples were also collected after an overnight fast and tested for total cholesterol, triacylglycerol, HDL-cholesterol and glucose. The subjects were interviewed about their physical activity and food intake during the trial and were instructed to follow a low fat diet of 1800 calories per day and keep a food record for seven days.
At the end of the 30 day trial, the Irvingia group had lost an average of 5.26 kilos (11.5 lbs) and the placebo group had lost only 1.32 kilos (2.9 lbs). The group receiving Irvingia also experienced a decrease in systolic blood pressure, total cholesterol, triglycerides and LDL cholesterol. HDL cholesterol increased.
This was the first study that suggested a weight loss benefit from Irvingia gabonensis. Why did the Irvingia group lose more weight? It's not clear, but in studies of free-living subjects, increased weight loss often means that the experimental group ate less, not necessarily from a direct action on metabolism, hormones or physiology.
In-credible weight loss research
In March of 2008, the same research group (Oben and Ngondi) published the results of their second study about Irvingia and weight loss. This time, Irvingia was combined with Cissus quadrangularis, a succulent vine native to West Africa and Southeast Asia. 72 subjects were divided into three groups, placebo, Cissus extract only (150 mg 2X/day) and Cissus-Irvingia combination (250 mg combined Cissus-Irvingia 2X/day).
All the same tests and measurements were taken as in the 2005 study. After 10 weeks, improvements were seen in total cholesterol, LDL cholesterol and fasting blood glucose. The placebo group lost 2.1 kg (4.6 lbs), the cissus group lost 8.82 kg (19.4 lbs) and the Cissus-Irvingia group lost 11.86 kg (26.1 lbs).
Attributing 26 pounds lost in 10 weeks solely to a fiber supplement is highly unlikely if not impossible, so the researchers (Oben and Ngondi) figured there was something else going on. They proposed that PPAR gamma, leptin, adiponectin or glycerol-3 phosphate dehydrogenase could all be potential mechanisms through which Irvingia gabonensis might affect body weight in overweight humans.
They set up another 10 week randomized double blind placebo-controlled study to investigate these possibilities. 120 subjects were divided into two groups; a placebo group and an Irvingia gabonensis group, which received 150 mg of Irvingia gabonensis extract twice a day.
Again, total and LDL cholesterol levels fell more in the Irvingia group than the placebo group (27% vs 4.8%). In the Irvingia gabonensis group, body fat decreased by 6.3% versus 1.9% in the placebo group. Weight decreased by 12.8 kg (28.1) pounds in the Irvingia gabonensis group vs 0.7 kg (1.5 lbs) in the placebo group. Favorable changes were also seen in Leptin (anti starvation hormone that signals brain & body about fat stores), adiponectin (protein secreted from fat cells; higher levels improve insulin sensitivity), C-reactive protein (marker of inflammation and cardiac risk) and fasting glucose.
To the lay person, this 28-pound weight loss (12.8 kilos) looks incredible. To someone familiar with research methods and weight loss research, these results look IN-credible, meaning NOT credible. To the informed and discriminating, results like these do not send you running to the health food store, they raise red flags, prompt more questions and demand more and better-controlled research.
What "controlled research" means
The subjects were advised not to alter their diet or activity, but that doesn't mean they didn't alter it anyways. These were free-living subjects, free to eat whatever they wanted and the only way the researchers knew how much the subjects ate or how active they were was from self-reported food and activity records. That's another way of saying the study was NOT controlled.
A true tightly-controlled weight loss study means that the subjects stay in a hospital or research center metabolic ward where all their food is prepared and delivered to them, which is the ONLY way to guarantee we actually know how much they ate. It also means that activity and exercise levels are monitored. Alas, none of these controls were used in this study and we have no way of knowing the true caloric intake or caloric expenditure of these subjects.
Explaining the anomaly
If these results are questionable, then how do we explain them? I mean, we're not saying the researchers are frauds, we're only suggesting that there were some anomalous findings which were parlayed into the latest supplement craze and a thriving business.
The main problem is that self-reporting of food intake is highly inaccurate and makes long term weight loss research very difficult to do. It's even possible that some subjects may have experienced a sort of "12 week fitness contest" type of effect, whereupon enrolling in the study, they wanted to impress anyone who saw the results. Therefore, they increased their exercise or activity in spite of instructions otherwise. Perhaps some of the subjects got sick and lost lean body mass. Maybe some were bloated and water retentive and simply dropped a lot of water weight. The explanations are endless.
But the story doesn't end here. There's another twist! It turns out that one person has done ALL the research to date and the same person owns the product rights.
Am I being overly skeptical?
Sure, I'm skeptical of weight loss supplements. That's because I'm intimately familiar with their sordid history and I read the research. In case anyone thinks I'm just trying to pick part this particular research only because I'm a diet pill party pooper and supplement skeptic, then think about the magnitude of the claim for a moment and decide for yourself:
The Dubious claim: "28 pounds of fat loss in 10 weeks with NO CHANGE IN DIET OR EXERCISE."
Let's do some math, shall we? 28 pounds of fat loss in 10 weeks = 98,000 calories, or 9,800 calories per week, or 1400 calories per day. So, the researchers and makers of this supplement are claiming that this product will raise metabolic rate by 1400 calories per day.
Is it a more reasonable assumption that an over-the-counter plant extract from an African tree caused astronomical increase in metabolism that probably no prescription drug comes close to, or that the research is flawed?
Consumers in the weight loss marketplace have such short memories. Doesn't anyone remember that last African wonder pill, hoodia? What happened to that one? And why another? How many of these products are already buried in the supplement graveyard? Haven't we learned our lessons from the past?
Irvingia Gabonensis: The bottom line
With an objective look at the evidence, we can probably conclude that Irvingia is a good source of fiber. Fiber can provide numerous health benefits and play a role in body fat control, but there are cheaper ways to get fiber than expensive African supplements, (starting with your food!) A 30-day supply of Irvingia (60 softgels at 150 mg each) currently retails for $42 to $72.
Future research might show that Irvingia Gabonensis and or an Irvingia and Cissus combination may provide significant health benefits. Existing research already suggests health benefits including cholesterol improvements, glycemic control, antibacterial actions and antioxidant properties. It's possible that some of the proposed anti-obesity benefits may also be confirmed. But at this time, the evidence is too thin to recommend Irvingia Gabonensis for weight loss beyond what you could get from any fiber product.
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