Five supplements that claim to speed up weight loss and what the science says

(MENAFN- The Conversation) 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.

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 inobese rats found raspberry ketones reduced their total body fat content . In one study, 70 adults with obesity were put on aweight loss diet and exercise program, and randomised to take a supplementcontaining 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.

Asmall pilot study of five adultsfound 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 aboutpotential toxic effects of raspberry ketoneson 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.

Read more: Do ketogenic diets help you lose weight?

Matchais 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. Areview of six studies using green tea preparations for weight lossover 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.

Read more: Science or Snake Oil: do skinny teas boost weight loss?

Garcinia Cambogiais a tropical fruit that contains a large amount ofHydroxycitric Acid(HCA), claimed to aid weight loss.

Inanimal studies , HCA interferes with usual production of fatty acids. If this was transferred to humans it could theoretically make it harder to metabolise fat and speed up weight loss. Research studies in humans show this is not the case.

While one12-week trial in overweight womenrandomised them to a low kilojoule diet, with or without HCA and found the HCA group lost significantly more weight (3.7 compared to 2.4 kilos for placebo), two other trials found no difference in weight loss.

A12-week trial in 135 men and womenfound no difference in weight loss between the HCA group (3.2 kilos) and the placebo group (4.1 kilos). Aten-week trial in 86 men and women who were overweightand 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.

Read more: Science or Snake Oil: is Garcinia cambogia the magic weight-loss pill it's hyped up to be?

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. Themore caffeine supplements consumed, the more the metabolic rate went up .

The lowest caffeine dose of 100mg, the amount in one instant coffee, increased the average metabolic rate by nine calories per hour, while the 400mg dose, which is roughly equivalent to the caffeine found in two to three cups of barista-made coffee, increased metabolic rate by about 34 calories per hour over three hours.

Whenadults with obesity were given caffeine supplementsat a dose of 8mg per kilo of body weight, there was an increase in metabolic rate of about 16% for up to three hours.

In a study in which adults with obesity were asked to follow a weight-loss diet, then randomised to receive either200mg caffeine supplements three times a day for 24 weeks or a placebo supplement , there was no difference in weight change between groups. For the first eight weeks, the group taking caffeine supplements experienced side-effects of insomnia, tremor and dizziness.

Verdict: Fiction! While caffeine does speed up the body's metabolic rate in the short-term, it does not speed up weight loss.

Read more: Health Check: four reasons to have another cup of coffee

Alkalising products are promoted widely. These include alkaline water, alkalising powders andalkaline diets . You're supposed to measure the acidity of your urine and/or saliva to 'assess' body acidity level. Urine usually has a slightly acidic pH (average is about pH6) –vegetables and fruit make it more alkaline, while eating meat makes it less so.

Saliva has a neutral pH of 7. Alkaline diets recommend you modify what you eat based on your urine or saliva pH, claiming a more alkaline pH helps digestion, weight loss and well-being.

Butyour stomach is highly acidicat a pH less than 3.5, with this acid helping breakdown food. It then moves into the small bowel fordigestion and absorption where the pH increasesto 4.5-5.0, which is still acidic.

Your body has finely controlled pH balancing mechanisms tomake 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 eatingby 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 withbetter long-term health .

Verdict: Fiction! There is no scientific evidence to support alkaline water or powders speeding up weight loss.

If you'd like to learn more about weight loss enrol in our free six week online course The Science of Weight Loss – Dispelling Diet Myths,here .

• Dieting
• weightloss supplements
• weightloss

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