The idea that there should be some magic bullet to weight loss is a surprisingly common one. This week, the magic cure the Mail is pushing is a type of crystal called “Sensa” which, it claims, makes food more flavoursome, so people eat less but feel as full. (Edit: The Telegraph is now reporting on it too, and their article is even more one sided than The Mail‘s)
So far, so what? Every diet pill on the planet claims to do that.
Ah, but, The Mail claims, there’s SCIENCE behind it:
In scientific tests, obese participants who used the flavourless, ‘Sensa Tastant’ crystals lost an average of two stones in six months.
Others lost an average of just two pounds.
Sure enough, the website of Sensa does provide links to the study, and it does appear to back up what the Mail claims at first glance. But there’s a problem.
The study, Use of Gustatory Stimuli to Facilitate Weight Loss, carries the name of just one scientist – Dr. Alan Hirsch. Hirsch happens to be not only the researcher who performed this experiment, but also the inventor of the crystals. One other study, “Efficacy Determination of Weight Loss through Use of Crystal Tastants“, claims to be by an independent lab, but there’s no authors listed for the study and it doesn’t appear anywhere on the internet apart from the Sensa website and a couple of mirrors, which makes this claim impossible to verify. In an interview with ABC News, Hirsch claims the second study was carried out by the distributor of the Sensa, in which case the researchers were perhaps less independent than implied.
Neither of these papers have published in a peer reviewed journal – nor, in fact are they proper papers. Instead, they’re just posters for use at a conference. As a result, they really don’t go into the experiments in any details, glossing over all the awkward details. For example, the papers do not give the distributions of weight loss. It’s all very good and well claiming that on average people lost on average 30 lbs, but unless you know what the spread is, it’s pretty useless. Did everyone lose 30 lbs, or did a few people lose 100 lbs and everyone else lose nothing?
Nor does it explain how the “control” group was controlled. In Hirsch’s study, there was no placebo. As far as I can tell, the control group is simply a collection of obese individuals who had no particular intention to lose weight. The people who actually took Sensa on the other hand were people who definitely did want to lose weight. Given that a) participants actually had to pay $49 per month to take part in the 6 month trial and b) people weren’t weighed in the lab but instead simply reported their weights to the scientists at the end of the study, there’s more than enough reasons for people to exaggerate their weight-loss to the researchers. Who wants to admit to wasting $300, after all?
Furthermore, only 1436 participants out of 2437 actually completed the trial; over 40% dropped out. It’s reasonable to assume that people who did not lose weight would stop taking the Sensa – after all, they’re paying $49 per month for it! This would weed out anyone who did not find Sensa worked and, over time, you’d be left only with the people who did lose weight – whether that was due to Sensa or not.
Finally, and most damningly, the experiments have never been peer reviewed. Dr Hirsch claimed at one point that the Endocrine Society had reviewed and approved his work. In fact, they simply allowed him to give a presentation at a conference, and were “surprised and troubled by the promotional nature of his presentation“.
ABC showed the papers to researchers, both professors at prestigious US university. One claimed the study has “negative value”, while the other said “says there is no scientific proof that Sensa works and believes the study was done to justify a commercial product”. Pretty damning.
It’s always possible that maybe a proper independent lab will pick up this study and prove without a doubt in a properly controlled experiment that Sensa works. At the moment though, I think it’s safe to say that the scientific evidence that the Mail so proudly touts is rather lacking.