There is insufficient evidence to justify recommending herbal and dietary supplements to help people lose weight.
This is the categorical view of the researchers who will present studies on the effectiveness of supplements at the European Congress on Obesity (ECO) to be held online this week.
“Although most supplements appear safe for short-term consumption, they will not lead to clinically meaningful weight loss,” said lead author Erica Bessell of the University of Sydney in Australia.
Herbal supplements contain whole plants or combinations of plants, while dietary supplements contain unique natural compounds. They can be purchased as pills, powders, and liquids and have become increasingly popular to help with weight loss.
A recent estimate suggested that 15% of Americans have tried a weight loss supplement in a $ 40 billion (£ 29 billion) industry worldwide. Yet there have been few recent attempts to review the scientific literature on all available herbal and dietary supplements.
Herbal supplements include green tea, white beans, ephedra (a stimulant that increases metabolism), African mango, yerba mate (an herbal tea made from the leaves and twigs of Ilex paraguariensis plant), licorice root and others.
To study the effectiveness of these and other supplements, Australian researchers performed a systematic review of all previous randomized trials in which the weight loss impact of herbal supplements was compared to the impact placebos. The data was analyzed for 54 studies involving 4,331 healthy, overweight or obese adults – and found that only one agent, white beans, caused statistically greater weight loss than a placebo.
In a separate study, the group analyzed previous trials that compared the effect of placebos with dietary supplements that included chitosan (made from the tough outer skeleton of shellfish); glucomannan (found in the roots of elephant yam, or konjac); fructan (a carbohydrate made up of chains of fructose); conjugated linoleic acid (which claims to change body composition by decreasing fat); and others.
Analysis found that chitosan, glucomannan, and conjugated linoleic acid resulted in weight loss, but not at clinically significant levels. In addition, certain other dietary supplements – including modified cellulose (a plant fiber that expands in induce a feeling of fullness) and blood orange juice extract – showed promising results but had only been studied in one trial. Much more evidence was needed before it could be recommended as a weight loss aid, the researchers concluded.
“Herbal and dietary supplements may seem like a quick fix to weight problems, but people need to be aware of how little we actually know about them,” Bessell said. “Very few high-quality studies have been done on certain supplements, with little data on long-term effectiveness.
“In addition, many trials are small and poorly designed, and some do not capture the makeup of the supplements studied. The enormous growth of the industry and the popularity of these products underscore the urgency of conducting larger and more rigorous studies to have reasonable assurance of their safety and effectiveness for weight loss.
Vegetarians less prone to disease
Vegetarians appear to have healthier disease profiles than meat eaters, according to a study of more than 166,000 UK adults, which will be presented at this week’s European Congress on Obesity.
“Our results offer real food for thought,” said Dr Carlos Celis-Morales of the University of Glasgow, who led the research. “In addition to not eating red and processed meats, which have been linked to heart disease and certain cancers, people who follow a vegetarian diet consume more vegetables, fruits and nuts, which contain more nutrients,” fiber and other potentially beneficial compounds.
“These nutritional differences may help explain why vegetarians appear to have lower levels of biomarkers that can lead to cell damage and chronic disease.”