High fat diet and exercise stimulate the breakdown of fats

Scientists report in the October issue of the Journal of Lipid Research that when either lean or obese individuals exercise after eating a high fat meal, their fats are broken down and oxidized in skeletal muscle, making them healthier.

These results show for the first time how a high fat diet and exercise stimulate the breakdown of fats and may help design ways to reduce excessive fat in the body.

Fat is broken down inside fat cells to generate energy by a process called lipolysis. The resulting fatty acids are released into the bloodstream and carried to tissues that require energy. In obese individuals, too much fat accumulates, compromising lipolysis, but the details of how this happens are not well understood. Also, obese individuals can show altered responsiveness to the stress hormones epinephrine and norepinephrine in their subcutaneous fat.

Max Lafontan and colleagues investigated how fat is broken down in both lean and obese subjects who exercised after either fasting or eating a high-fat diet. They noticed that after eating a high-fat diet, fats were broken down in both lean and obese individuals. Under fasting conditions, the breakdown of fats was more pronounced in the lean subjects, but the high fat meal enhanced lipolysis in the obese subjects.

The scientists also studied the effects of long-chain fatty acids (LCFAs) – which are found in high fat diet – on cultured fat cells. They noticed that LCFAs increase lipolysis when it is induced by epinephrine, one of the hormones known to stimulate lipolysis.

By showing for the first time how a high fat diet and LCFAs affect hormone-induced lipolysis in fat cells, this study paves the way for further research on the role of various fatty acids on the metabolism of muscle and blood vessel cells, the researchers conclude.

Article: “Acute exposure to long-chain fatty acids impairs alpha2-adrenergic receptor-mediated antilipolysis in human adipose tissue,” by Jan Polak, Cedric Moro, David Bessiere, Jindra Hejnova, Marie A. Marques, Magda Bajzova, Max Lafontan, Francois Crampes, Michel Berlan, and Vladimir Stich (http://www.jlr.org/cgi/content/abstract/48/10/2236).

The American Society for Biochemistry and Molecular Biology is a nonprofit scientific and educational organization with over 11,900 members in the United States and internationally. Most members teach and conduct research at colleges and universities. Others conduct research in various government laboratories, nonprofit research institutions and industry. The Society's student members attend undergraduate or graduate institutions.

Founded in 1906, the Society is based in Bethesda, Maryland, on the campus of the Federation of American Societies for Experimental Biology. The Society's purpose is to advance the science of biochemistry and molecular biology through publication of the Journal of Biological Chemistry, the Journal of Lipid Research, and Molecular and Cellular Proteomics, organization of scientific meetings, advocacy for funding of basic research and education, support of science education at all levels, and promoting the diversity of individuals entering the scientific work force.