When you google “weight loss” the challenge to sort fact from fiction begins. These five supplements claim to speed up weight loss, but let’s see what the evidence says.
1. Raspberry ketones
Raspberry ketones, sold as weight loss tablets, are chemicals found in red raspberries responsible for that distinct raspberry flavour and smell. You can also make raspberry ketones in a lab.
A study in obese rats found raspberry ketones reduced their total body fat content. In one study, 70 adults with obesity were put on a weight loss diet and exercise program, and randomised to take a supplement containing either raspberry ketones, or other supplements such as caffeine or garlic, or a placebo.
Only 45 participants completed the study. The 27 who took a supplement lost about 1.9 kilos, compared to 400 grams in the 18 in the placebo group. The drop-out rate was so high that these results need to be interpreted with a lot of caution.
A small pilot study of five adults found no effect on weight when the participants were told to maintain their current eating and exercise patterns and just took supplements of 200mg/day of raspberry ketones.
Concerns have been raised about potential toxic effects of raspberry ketones on the heart and for reproduction.
Verdict: Fiction! Leave the raspberry ketone supplements on the shelf. Spend your money on foods that contain them, including fresh berries, kiwifruit, peaches, grapes, apples and rhubarb.
2. Matcha green tea powder
Matcha is a green tea made from leaves of the Camellia sinensis, or tea plant, but it’s processed into a green powder and can be mixed into liquids or food. Before the leaves are harvested, the tea plant is put in the shade for a few weeks, which increases the content of theanine and caffeine.
No studies have tested the effect of matcha on weight loss. A review of six studies using green tea preparations for weight loss over 12 weeks found a difference based on country. In studies conducted outside of Japan, people consuming green tea did not lose more weight than controls. In the eight studies conducted within Japan, the mean weight loss ranged from 200 grams to 3.5 kilos in favour of green tea preparations.
Verdict: Fiction! There are currently no studies testing whether matcha tea accelerates weight loss.