MD, PhD, FMedSci, FSB, FRCP, FRCPEd

slimming aids

Pyruvate, a ketone and an alpha-keto acid, occurs naturally in the body when glucose is converted into energy. It is part of the Krebs cycle, the complex chain of reactions in which nutrients are metabolised to provide energy. High doses of pyruvate seem to stimulate the breakdown of fat in the body. It is therefore not surprising that pyruvate is used in all sorts of slimming aids; and if the advertising for ‘fat burners’ is to be believed, pyruvate is just the ticket for the desperate slimmer.

One such product advertisement, for instance, claims that sodium pyruvate and potassium pyruvate, which can act as a stimulant for the metabolism, adding to the thermogenesis process. Pyruvates have been found in studies to reduced the storage of fat in the body and convert the food source into calories which are then burned off in the production of heat. In one study, rats were injected with three fat burners, including pyruvates, and the rats given the pyruvates burned the greatest amount of fat by increasing the rat’s resting metabolic rate. With the elevated resting metabolic rate, the body burned more fat in individuals, which makes pyruvate an excellent source for weight maintenance.

So, maybe pyruvate works for rats – but does it really help those of us who would like to lose a few kilos? Some studies seem to say so, but others don’t. What do we conclude? There can only be one solution: we need a systematic review of the totality of the available trial evidence – and you probably guessed it: we have just published such an article.

The objective of our systematic review was to examine the efficacy of pyruvate in reducing body weight. Extensive literature searches identifies 9 RCTs of which 6 were met our inclusion criteria. All had methodological weaknesses. The meta-analysis revealed a statistically significant difference of 0.72 kg in body weight with pyruvate compared to placebo. The magnitude of the effect is small, and its clinical relevance is therefore uncertain. Adverse events included gas, bloating, diarrhoea, and increase in low-density lipoprotein cholesterol.

Our conclusion: The evidence from randomized clinical trials does not convincingly show that pyruvate is efficacious in reducing body weight. Limited evidence exists about the safety of pyruvate. Future trials involving the use of this supplement should be more rigorous and better reported.

Pyruvate supplements are popular; people who want to lose weight are misled into believing that they are effective. Bodybuilders as well as other athletes tend to take them because pyruvate is claimed to reduce body fat and enhance the ability to use energy more efficiently. None of these assumptions is based on sound evidence. Regardless of the evidence, a whole industry is exploiting the gullible and doing very well on it.

As these ‘fat burners’ are by no means cheap, I recommend a more efficient and more economical method for normalising body weight: eat a little less and move a bit more - I know it’s naff, but it works!

The developed world is in the middle of a major obesity epidemic. It is predicted to cause millions of premature deaths and billions of dollars, money that would be badly needed elsewhere. The well-known method of eating less and moving more is most efficacious but sadly not very effective, that is to say people do not easily adopt and adhere to it. This is why many experts are searching for a treatment that works and is acceptable to all or at least most patients.

Entrepreneurs of alternative medicine have long jumped on this band waggon. They have learnt that the regulations are lax or non-existent, that consumers are keen to believe anything they tell them and that the opportunities to make a fast buck are thus enormous. Today, they are offering an endless array of treatments which are cleverly marketed, for instance via the Internet.

Since many years, my research team are involved in a programme of assessing the alternative slimming aids mostly through systematic reviews and occasionally also through conducting our own clinical trials. Our published analyses include the following treatments:

Phaseolus vulgaris

Supplements containing conjugated linoleic acid

Green tea

Garcinia extracts

Calcium supplements

Chromium picolinate

Guar gum

Chitosan

Acupuncture

There are, of course, many more but, for most, no evidence exist at all. The treatments listed above have all been submitted to clinical trials. The results show invariably that the outcomes were not convincingly positive: either there were too few data, or there were too many flaws in the studies, or the weight reduction achieved was too small to be clinically relevant.

Our latest systematic review is a good example; its aim was to evaluate the evidence from randomized controlled trials (RCTs) involving the use of the African Bush Mango, Irvingia gabonensis, for body weight reduction in obese and overweight individuals. Three RCTs were identified, and all had major methodological flaws. All RCTs reported statistically significant reductions in body weight and waist circumference favoring I. gabonensis over placebo. They also suggested positive effects of I. gabonensis on blood lipids. Adverse events included headache and insomnia. Despite these apparently positive findings, our conclusions had to be cautious: “Due to the paucity and poor reporting quality of the RCTs, the effect of I. gabonensis on body weight and related parameters are unproven. Therefore, I. gabonensis cannot be recommended as a weight loss aid. Future research in this area should be more rigorous and better reported.”

People who want to loose weight are often extremely desperate and ready to try anything. They are thus easy victims of the irresponsible promises that are being made on the Internet and elsewhere. Despite the overwhelmingly evidence to the contrary, consumers are led to believe that alternative slimming aids are effective. What is more, they are also misled to assume they are risks-free. This latter assumption is false too: apart from the harm done to the patient’s bank account, many alternative slimming aids are associated with side-effects which, in some cases, are  serious and can even include death.

The conclusion from all this is short and simple: alternative slimming aids are bogus.

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