We speak often of the negative health effects of diets high in fat and sugar, but a new study published in the FASEB Journal may hold the answer to exactly how these effects occur.

Not only are high-fat, high-sugar foods harder to convert to energy, they also stimulate a gene called the kappa opioid receptor (KOR), which is believed to play a key role in fat metabolism. Over time the receptor over-stimulated, causing our bodies become more and more efficient at storing fat.

To make this discovery, researchers Czyzyk, Nogueiras, et al. tested two groups of mice. The control group (KO) had the KOR genetically deactivated, while the other group (wild-type, or WT) remained normal. Both groups were fed an identical high fat, high sugar, energy dense diet (HED) for 16 weeks. 

After 16 weeks, the KO group had 28% lower body weight, 45% lower fat mass, better glycemic control, and higher energy expenditure compared to the WT group. According to the researchers, these results provide the first evidence that KORs play a key role in fat storage. Although more study is needed to confirm the role of KORs human, these findings may hold the key to finding a solution to the current obesity epidemic.

Reference: Traci A. Czyzyk, Ruben Nogueiras, John F. Lockwood, Jamie H. McKinzie, Tamer Coskun, John E. Pintar, Craig Hammond, Matthias H. Tschöp, and Michael A. Statnick. κ-Opioid receptors control the metabolic response to a high-energy diet in mice. The FASEB Journal, 2009; DOI: 10.1096/fj.09-143610