CLARE COLLINS, LEE ASHTON & REBECCA WILLIAMS, THE CONVERSATION8 DEC 2019
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 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 200 milligrams/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.
B 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.
Verdict: Fiction! There are currently no studies testing whether matcha tea accelerates weight loss.
3. Garcinia cambogia supplements
A ten-week trial in 86 men and women who were overweight and randomised to take either Garcinia cambogia extract or placebo, but were not also put on a weight-loss diet, found minimal weight loss of 650 grams versus 680 grams, with no difference between groups.
Verdict: Fiction! Garcinia cambogia does not accelerate weight loss.
4. Caffeine supplements
Caffeine is claimed to increase your metabolic rate and therefore speed up weight loss.
Research studies in volunteers of a healthy weight found an increase in metabolic rate, but it depended on the dose. The more caffeine supplements consumed, the more the metabolic rate went up.
Verdict: Fiction! While caffeine does speed up the body's metabolic rate in the short-term, it does not speed up weight loss.
5. Alkaline water
Alkalising products are promoted widely. These include alkaline water, alkalising powders and alkaline diets.
Your body has finely controlled pH balancing mechanisms to make sure your blood pH stays between 7.35 - 7.45. If it did not, you would die.
On the positive side, alkaline diets encourage healthier eating by promoting plant based foods such as fruit and vegetables.
There is some evidence lower intakes of foods of animal origin that contribute to acid load are associated with better long-term health.