There is insufficient evidence to justify recommending herbal and dietary supplements to help people lose weight.
That is the emphatic view of the researchers who will present studies on the effectiveness of supplements in the European Obesity Congress (ECO) to be held online this week.
“Although most supplements appear safe for short-term use, they are not going to provide clinically significant 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 compounds of natural origin. They can be purchased in the form of pills, powders, and liquids and have become increasingly popular as weight loss aids.
A recent estimate has suggested that 15% of Americans have tried a weight loss supplement in an industry valued at $ 40 billion (£ 29 billion) worldwide. However, 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 (a herbal tea made from the leaves and twigs of the Ilex paraguariensis plant), licorice root and others.
To study the efficacy of these supplements and others, Australian researchers conducted a systematic review of all previous randomized trials comparing the impact of herbal supplements on weight loss with the impact of placebos. Data from 54 studies involving 4,331 healthy, overweight or obese adults were analyzed, revealing that only a single agent, navy beans, resulted in statistically greater weight loss than a placebo.
In a separate study, the group looked at previous trials that compared the effect of placebos with dietary supplements that included chitosan (made from the hard outer skeleton of shellfish); glucomannan (found in the roots of elephant yam or konjac); fructan (a carbohydrate made up of fructose chains); conjugated linoleic acid (which claims to change body composition by reducing fat); and others.
The analysis found that chitosan, glucomannan, and conjugated linoleic acid produced weight loss, but not at clinically significant levels. Also, some other dietary supplements, including modified cellulose (a plant fiber that expands in the stomach to induce a feeling of fullness) and blood orange juice extract – showed promising results, but had only been investigated in one trial. Much more evidence is needed before they can be recommended as weight loss aids, the researchers concluded.
“Herbal and dietary supplements may seem like a quick fix to weight problems, but people should be aware of how little we know about them,” Bessell said. “Very few high-quality studies have been done on some supplements, with little data on long-term effectiveness.
“Also, many trials are small and poorly designed, and some do not report on the composition of the supplements being investigated. The tremendous growth in the industry and the popularity of these products underscores the urgency for larger and more rigorous studies to have a reasonable assurance of their safety and efficacy for weight loss. “
Vegetarians less prone to disease
Vegetarians appear to have healthier disease profiles than carnivores, according to a study of more than 166,000 UK adults, to be presented at this week’s European Obesity Congress.
“Our findings 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 meat, which has been linked to heart disease and some 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.”