Raspberry ketone has gained an enviable reputation for boosting weight loss. Raspberries are among the tastiest of fruits and raspberry ketone, or frambinone, is among the 230 volatile components which give raspberries their lovely, characteristic scent. Open a bottle of raspberry ketone supplements, inhale, and you will instantly recognise the unique sweet aroma. Raspberry ketones are widely promoted for weight loss, but is there any evidence that it works?
Can raspberry ketones burn fat?
Weight gain in later life is associated with an increase in the number of fat cells in the body. Known as adipogenesis, this expansion in the size and number of fat cells (adipocytes) involves many different cell receptors and the activation of several genes.
Once fat cells are mature, they produce fat when you eat more calories than you burn. This is fuelled by following a high carbohydrate diet, and the effects of insulin which escorts glucose into fat cells for conversion to fat for storage.
Raspberry ketones have the potential to act as an anti-obesity agent by:
- Inhibiting the absorption of dietary fat in the small intestine
- Stimulating the metabolism of white fat cells so that more fat is broken down
- Stimulating the metabolism of brown fat cells so that more fat is burned to generate heat.
These findings initially came from laboratory studies using human fat cells, and mice. Raspberry ketones have now been tested in human volunteers.
Raspberry ketones research
In an 8-week study, 70 obese but otherwise healthy men and women (aged 21 – 45 years) took a supplement containing a blend of raspberry ketones plus caffeine, capsaicin, garlic, ginger, Citrus aurantium and B vitamins (all of which have some evidence for aiding fat metabolism) or an inactive placebo. Everyone taking part in the study also followed a low-calorie diet and a regular exercise program (one hour, three times a week).
Volunteers were given a precise menu to follow that provided 3 meals and 2 snacks per day, and were phoned every week to assess how well they were keeping to the diet and taking the raspberry ketone supplement blend.
Perhaps surprisingly, only 45 people completed the study but this was not because of unwanted side effects: 11 did not follow the diet properly, 12 didn’t take the supplements, 7 didn’t like the exercise program, 4 were no longer interested and 1 withdrew because of pregnancy.
Of the 45 people who finished the study, 27 were taking the raspberry ketone supplement blend, and 18 were taking the placebo. Those taking the raspberry ketone blend lost significantly more weight than those taking placebo, importantly they lost more fat mass and gained more lean muscle, as well as showing significant improvements in waist and hip measurements.
The results after 8 weeks, were as follows:
Not an overly impressive result in the placebo group given that they were following a low-calorie diet and exercising for 8 weeks! This may explain why so many in the placebo group gave up.
Those taking the raspberry ketone supplement also recorded a statistically significant increase in relative energy levels over those taking placebo (+29.3% versus +5/1%) and a significant decrease in cravings for fatty foods (-13.9% versus -0.9%). There were no significant differences in cravings for sweet, fast food fats, carbohydrates or healthy foods.
The researchers concluded that the raspberry ketone blend was a safe and effective adjunct to an eight-week diet and exercise weight loss program, which improved changes in body composition, waist and hip girth.
Raspberry ketones side effects
All volunteers in the above study underwent blood tests before and after the study and there were no changes in blood chemistry. No adverse events were recorded.
Raspberry ketones remain available on the internet because there are no serious safety concerns at the typical doses used of 100mg to 1,400mg per day.
Some researchers urge caution as the upper safe level at which toxic effects might occur (above 280mg per kilogram body weight per day) requires further study.
Raspberry ketone supplements
We still don’t know how effective raspberry ketones are on their own rather than in a blend of other natural weight loss boosting ingredients. If you decide to take a raspberry ketone supplement, it is important to also follow a weight loss diet and to exercise to help boost fat loss and preserve lean muscle. For most people, following a low glycemic diet is most effective.
Always follow the dose instructions on the label, as different products contain different concentrations of raspberry ketones and other weight-loss promoting ingredients.
Even if you decide not to try a raspberry ketone supplement, you can include fresh raspberries in your diet. Raspberries contain relatively little sugar and are low in calories, typically supplying just 53 kcals per 100g. They are a rich source of fibre, and of antioxidants, including vitamin C and polyphenols that contribute to their delicious aroma, taste and colour.
Red raspberries provide 155mg polyphenols per 100g, while black raspberries supply as many as 980mg per 100g.
Have you tried raspberry ketones for weight loss? Did you find them effective?