Raspberry Ketones – Weight Loss Facts and Fiction

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What is Raspberry Ketone?

Raspberry ketone is a very common ingredient found in widely used dietary weight loss supplements, but does it work, is it safe and is it worth the price?

Raspberry ketone (Rheosmin or RK for short; aka 4-(4-hydroxyphenyl) butan-2-one) is a phenolic compound with a fruity aroma from the red raspberry (Rubus idaeus), other fruits and the bark of some trees.  RK’s chemical structure is similar to capsaicin (found in cayenne pepper) and synephrine (a replacement for ephedrine after being banned by the FDA).

The importance of understanding RK’s chemistry and similarity to capsaicin and synephrine is because of the relatively scant research available on RK.  Claims that RK has no side effects must be considered with cautioned as always and remember the principle of ‘caveat emptor’ or ‘let the buyer beware’.  Perhaps at low doses this is true, but it is important to understand that it is known that synephrine, which is a sympathomimetic drug, may have cardiovascular toxicity. It is also important to understand that capsaicin also has sympathomimetic activity and may have similar effects and toxicity.  RK has been shown to inhibit the anticoagulant activity of warfarin (such as Coumadin, Marevan and Jantoven) in vitro, so this should be discussed with your healthcare provider prior to use in patients on these types of medications.

RK has been used for various purposes including: a very expensive flavoring for food, fragrance in the cosmetics industry, and it has even been used as an attractant for male melon flies in mating experiments. Red raspberries have a relatively low concentration of RK, so most of the available RK on the market is produced through microbial synthesis and derived from sources such as tree bark (pine, maple, and yew), rhubarb, grapes, apples and peaches.

The Weight Loss Hype

Although RK has been around for a long time, since at least the early 1920’s for its various uses, it has gained considerable notoriety over the last few years. The Internet was a buzz with RK reports in 2012 when Dr. Oz featured an advertisement for the “Miracle Fat Burner Bottle”.  Since that time there have been numerous articles related to RK and many products made available both online and offline.

Tip! RK has not been adequately studied in humans and the products sold claiming a weight loss benefit require the familiar FDA disclaimer.

The Weight Loss Facts

If you happen to be a lab mouse or rat that can read, RK is for you!  In other words, there is a paucity of highly reliable studies available on human subjects.

Having pointed out that there are insufficient studies to make solid claims on the effectiveness of RK for weight loss in humans, animal studies do show a positive effect.  One study1 of RK’s anti-obese action in mice revealed, “RK prevents and improves obesity and fatty liver.”  Another study2 revealed that RK might have the beneficial effects of fat reduction and liver protection through its affect on adiponectin in rats that were fed a high-fat diet.

One human study3, where the primary authors received competing interests for research funding and as consultants for dietary supplement companies (Tip! – usually a red flag), found that RK may have a more “robust” effect compared to a placebo group on in reducing hip and waste girth in men and women over an eight (8) week time period, which also included a diet and exercise regimen.  The study used a branded supplement containing not only RK, but also caffeine, capsaicin and other ingredients.  Caffeine and capsaicin may also have been a factor in any hip and waste girth reduction between the study and control groups, so it is impossible to determine RK’s specific role in this possible beneficial effect.

Bottom Line

RK may be safe for most people and it may even help, but at a cost of $25 to $55 a month its ultimate value will have to be assessed by the individual results of its user.  Certainly, when combined with the diet and exercise most vendors recommend there is some benefit.

In summary, raspberry ketones may play some beneficial role in burning fat – and cash, although the marketed supplements that include other ingredients such as caffeine and capsaicin blur its specific effect.  The safest of weight loss tips and tricks is to begin with a healthy diet and exercise.



1.        Life Sci. 2005 May 27;77(2)): 194-204.

2.         J. Med. Food. May 2012; 15(5): 495-503.

3.        J. Int’l. Soc. of Sports Nutrition 2013, 10:22.



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