Raspberry Ketones and Increased Parameters of Fat Metabolism
Ever think of eating more raspberries to help increase your body's ability to burn fat?  It turns out a key ingredient found in the tasty fruit has properties that a couple of preliminary studies suggest may help to increase fat breakdown and limit fat accumulation.  The substance itself is called raspberry ketones that most commonly have been used as a fragrance in cosmetics and as a flavoring agent in various types of foods.  Another popular weight loss ingredient is capsaicin, the pungent ingredient found in peppers and spicy foods that give these types of food their fire or hot sensation upon ingestion.  
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A number of research studies have been published using both animal and human research subjects which indicate that capsaicin can help improve energy expenditure, increase fat burning and minimize fat accumulation.  Scientists became interested in raspberry ketones because structurally they are very similar to capsaicin, but they lack the spicy or pungent effect.  The first study to examine the impact of raspberry ketones on its ability to prevent weight gain provided various doses of raspberry ketones to laboratory mice and fed them a high-fat diet.  Turns out providing high levels of raspberry ketones in the animals diet helped to reduce weight gain and also increased the amount of lipolysis or fat breakdown in fat cells found in the animals [1].  Several years passed before another study was conducted and recently scientists exposed fat cells to raspberry ketone in an effort to examine what exactly was responsible for the prevention in weight gain and increase in fat breakdown as seen in the initial study.  When exposed to fat cells, raspberry ketone significantly increased the amount of lipolysis or fat breakdown in fat cells.  A follow-up analysis revealed that raspberry ketones favorably increased the expression of adiponectin, an important hormone released primarily by fat cells.  In humans, increased levels of adiponectin are associated with reduced levels of obesity and the metabolic syndrome. 

Equally important, exposing fat cells to raspberry ketone decreased the amount of fat which accumulated in the fat cells, which is a favorable change linked to reduction in overall body fat.  The authors concluded that raspberry ketone holds great promise for its ability to both reduce fat accumulation and increase fat breakdown [2].  In closing, two studies in animals or fat cells provide interesting and encouraging data to indicate that raspberry ketones may be an important ingredient for its ability to increase fat breakdown and reduce the accumulation of fat in fat cells.  Certainly, additional research is needed to further confirm these results in humans to see if they can be used as an aid to help lose fat and control your body composition.

1. Morimoto, C, Satoh, Y, Hara, M, Inoue, S, Tsujita, T, and Okuda, H. Anti-obese action of raspberry ketone. Life Sci. 2005; 77(2): p. 194-204.
2. Park, KS. Raspberry ketone increases both lipolysis and fatty acid oxidation in 3T3-L1 adipocytes. Planta Med. 2010; 76(15): p. 1654-8.