New research evaluating the effectiveness of a broad selection of popular slimming supplements sold in pharmacies and health food shops has found no evidence that any of them facilitate weight loss. The findings from two studies into over-the-counter supplements were presented this week at the International Congress on Obesity in Stockholm, Sweden.
"There are scores of slimming supplements out there claiming weight-loss effects through all sorts of mechanisms of action. We have so-called fat magnets, mobilizers and dissolvers, as well as appetite tamers, metabolism boosters, carb blockers and so on. The market for these is huge, but unlike for regulated drugs, effectiveness does not have to be proven for these to be sold," said researcher Dr. Thomas Ellrott, from the University of Göttingen, Germany. "Few of these supplements have been submitted to clinical trials and the landscape of products is always changing, so we need to put them through rigorous scientific evaluation to determine whether they have any benefit."
Ellrott's group tested nine popular supplements against placebo pills in a randomized controlled trial. The supplements tested included L-Carnitine, polyglucosamine, cabbage powder, guarana seed powder, bean extract, Konjac extract, fibre pills, sodium alginate formulations and selected plant extracts.
Average weight loss was between 1 kg and 2 kg across seven of the products, depending on the supplement, and was 1.2 kg in the group getting the placebo pills. No statistically significant difference in weight loss was found for any of those products when compared with the placebo.
"Most previous studies have examined only one product. This is the first to include nine supplements with different proposed mechanisms of action and we found that not a single product was any more effective than placebo pills in producing weight loss over the two months of the study, regardless of how it claims to work," Ellrott said.
In the second study, Dr. Igho Onakpoya of the Universities of Exeter and Plymouth, UK, conducted the first systematic review of all clinical trials on weight loss supplements. The analysis summarizes the state of evidence from reviews of studies involving nine popular slimming supplements, including chromium picolinate, Ephedra, bitter orange, conjugated linoleic acid (CLA), calcium, guar gum, glucomannan, chitosan and green tea.
"We found no evidence that any of these food supplements studied is an adequate treatment for reducing body weight," Onakpoya said. "Annual global sales of dietary supplements are well over $13 billion. The weight-loss industry in North America is worth over $50 billion and Americans spend over $1.6 billion a year on weight-loss supplements. People think these supplements are a short cut to weight loss and may spend huge sums of money on them, but they may end up disappointed."
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Source: International Association for the Study of Obesity