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 ketone is widely promoted for weight loss, and there is some evidence that it works.

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Raspberry ketone burn fat to increase weight loss

Raspberry ketone increases the metabolic rate so that more fat is burned as fuel and more calories are used to generate heat and boost weight loss.

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 mature, they store fat when you eat more calories than you burn. This is promoted by following a high carbohydrate or high glycaemic index diet, as these trigger the release of insulin. Insulin is the main fat-storing hormone in the body, as it escorts glucose into fat cells where excess is converted into fat stores.

helps to reduce fat storing, and has been hailed as an anti-obesity agent. Raspberry ketone helps to increase weight loss in three ways:

• 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.

Raspberry ketone may also protect against fatty liver disease.

These findings initially came from laboratory studies using raspberry ketone on human fat cell cultures, and in mice. Raspberry ketone has now been tested to assess its effects on weight loss in human volunteers, in a combination product.

Raspberry ketone for weight loss

In an 8-week weight loss study, 70 obese but otherwise healthy men and women (aged 21 – 45 years) took a supplement containing a blend of raspberry ketone plus caffeine, cayenne 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 raspberry ketone weight loss study also followed a low-calorie diet and a regular exercise program (for 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 weight loss results after 8 weeks, for those taking the raspberry ketone blend compared with the placebo 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 between those taking raspberry ketone or placebo.

The researchers concluded that the raspberry ketone blend was a safe and effective addition to an eight-week diet and exercise weight loss program, and improved body composition, waist and hip girth.

Raspberry ketone side effects

All volunteers in the raspberry ketone study underwent blood tests before and after and there were no changes in blood chemistry. No adverse events were recorded.

Raspberry ketone supplements 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 with raspberry ketone 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 ketone is on its 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.

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Image credits:  dglodowska/pixabay;  johanna84/pixabay