If you read the ads and are left with the impression that simply popping a few pills could be the answer to all your weight worries, there are some things you should know:
How good is the evidence these products, or at least their ingredients, can really make you lose weight?
The evidence for the most common ingredients we found isn’t very convincing, though some look more promising than others. We searched the medical literature for the evidence on 10 common weight-loss ingredients found in three or more of the 18 products we looked at.
What the companies said. We asked the 10 distributor companies (the Therapeutic Goods Administration calls them ‘sponsors’) of the 18 products we looked at for evidence to support their products’ efficacy:
- Only four sent supporting documentation of some kind.
- This didn’t add greatly to the information we’d collected through research sources.
- It wasn’t uncommon for a sponsor to send selected published papers that supported a positive finding for their ingredients, while ignoring the overall body of evidence, which was mixed.
- Some sponsors sent unpublished trial information for their product, but generally these weren’t good-quality trials.
One company sent a small short-term trial on its product (OPTISLIM) that found a positive effect, although there wasn’t much detail on exactly how it was conducted. To be convincing evidence, it would need to be replicated in large-scale, double-blind, controlled clinical trials with overweight and obese people over a longer period of time.
It’s possible that certain combinations of ingredients could have a greater effect than each one on its own, in theory. But although a couple of sponsors sent trials of their product’s particular combination, the published evidence for various combinations of herbs is no more convincing than the evidence for single ingredients. While other unpublished trials may exist, if they do the sponsors decided not to share them with CHOICE.
In general, treat claims for significant weight loss with caution. Overall the evidence isn’t strong and we haven’t seen any good-quality evidence of efficacy for the products themselves, never mind some of the ingredients.
Safety data is limited in general, and what’s been found is often from short-term studies. Many of these ingredients have a history of long-term use, but sometimes not in the same dose or form.
The Federal Government’s expert body (National Health and Medical Research Council, NHMRC) advises GPs treating overweight people:
“A wide range of alternative treatments is available. However, there is no evidence of significant long-term weight loss from any of these. Patients should be advised about the lack of evidence for using over-the-counter weight-loss medications and, in some cases, the dangers of using them.”
What's good quality evidence?
As a minimum, studies should:
- Be large: testing a large number of people in the target group.
- Be placebo controlled: have a control group who get a dummy pill (placebo).
- Be blind: neither the participants, nor the researchers should know who's taking the real pills until the study is complete.
- Be randomised: The particpants should be randomly put in the control or test group.
- Be peer-reviewed and published: The results should be reported in detail (with statistical analysis) in peer-reviewed, well-respected journals.
Multiple studies should support the outcome.
This article last reviewed December 2005