Kiwi diet pill claims – experts respond

The company behind a new New Zealand weight loss product claim their latest clinical trial shows the pill works — but experts say more rigorous studies are needed to show it is actually effective.

Satisfax, a blend of grape and kiwifruit extracts, was developed by Tuatara Natural Products as a weight loss aid which slows digestion, leaving people feeling full after eating less. The product has received some media attention over the summer thanks to Tuatara’s “100 Fat Mates” trial.

In a media release issued today, the company highlighted the results of the trial, which recruited 100 overweight participants take Satisfax capsules over eight weeks. Participants were not asked to change their diet, exercise or lifestyle.

According to the release: “Most reported eating less of the same food and were now able to exercise. Of the 52 triallists who took the recommended dose for the full eight weeks 46 lost weight, averaging close to 3kg, with the top 26 losing an average of 5kg. Two lost over 10kg.”

“The success of Satisfax as a weight management tool is beyond our expectations,” said Dr Glenn Vile, Tuatara Natural Product’s Chief Technical Officer, in the media release.

“Satisfax did not work for everyone, but overall we can be very confident that -­ for most people – Satisfax has proven to be a very valuable tool to assist weight loss and weight management.”

A commissioned independent analysis of the data from the trial is available on the Tuatara Natural Products website.

The SMC collected the following expert commentary. Feel free to use these quotes in your reporting. If you would like to contact a New Zealand expert, please contact the SMC (04 499 5476;

Assoc Prof Andrew Jull, Senior Research Fellow, National Institute of Health Innovation, University of Auckland, comments:

“This is the kind of trial that is early phase of testing. It is not the type of trial that would be accepted by regulatory agencies as showing Satisfax is effective for weight loss. There are some problems with this evidence – there was no control group to show normal weight loss and only 81 out of the 100 people in the trial were included in the analysis*.

“This product may be a promising development, but only for further testing. It is not a solution currently.  What we really need is a large randomised controlled trial, where one group has product and the other group has a placebo, and nobody knows which product they are taking. ”

*Tuatara Natural Products responded that design of the trial included defining the group of participants that would be included in the statistical analysis and this was based on their participating in the trial for the full 8 weeks.  On this basis 81 participants were included.

Prof Thomas Lumley, Professor of Statistics, University of Auckland, comments:

“The Satisfax study had no control group and no masking: everyone was getting the novel product and knew they were. It’s likely at least part of the observed effect is due to trying something new and expecting (or hoping) that it will work. It’s hard to say how much — that’s why randomised controlled trials are standard for evaluating new treatments in settings where demonstrating effectiveness is important. It’s also important to note that this was a very short study. For example, FDA guidelines for studying weight loss treatments recommend assessing weight loss at one year.

“The press release makes this worse. It gives the average weight loss for 52 people who took all the capsules, and the average for the best 26 of those who took all the capsules, and the largest weight loss. It does not give the average weight loss for all participants. In the ‘full’ analysis (still only of 82 people), the mean weight loss was 2.3kg with 95% confidence interval from 1.5 to 3kg. The potential size of the uncontrolled-trial bias is thus important.

“In January, earlier publicity for the study in the Marlborough Express said there would be an analysis that corrected for the bias of having an uncontrolled, open-label trial, so the company is aware that this bias important to understanding the results. This analysis is not even mentioned in the press release.

“It’s hard to estimate the plausible range of bias, since most published data are from randomised controlled trials. The full analysis used the weight loss in the placebo group in randomised controlled trials as an estimate of the uncontrolled-trial bias. This isn’t ideal — you might expect the real bias to be larger — but it’s reasonable thing to try. The full analysis points to a recent review of some of these controlled trials. In the trials with a 6-12 weeks duration the average weight loss in the placebo groups was most often less than 1kg, but in one trial the average loss in the placebo group was 4.3kg**.

“Given the short duration of the trial and the lack of a control group, this isn’t strong evidence of any benefit from Satisfax, and how the results have been reported does not lead to increased confidence. This study was a reasonable next research step, but it is misleading to promote it as successful clinical trial or an “answer to one of the world’s greatest and fastest growing problems.”

**Tuatara Natural Products has pointed out that this placebo group was placed on a high-fiber, low-energy diet