Ever wonder why you're still hungry on Monday after splurging on fatty, "forbidden" foods -- think that juicy double cheeseburger topped off with a thick vanilla shake -- over the weekend? The fat contained in junk food treats may be changing the chemicals in your brain, not your arms or hips, and in a very short amount of time too.

Palmitic acid, one of the more common saturated fats found in dairy products and meat, is the culprit, based on a study of mice at the University of Texas Southwestern.

Before this discovery, even though it was well known that consuming a high-fat diet promoted insulin resistance, little was known about the mechanisms that triggered this problem. That led scientists to speculate if the brain -- an organ that soaks up some of the fats we eat -- could play a role.

After comparing the effect of three fats on the brains of mice (palmitic, oleic and monosaturated fatty acids), palmitic acid was found to reduce the appetite-suppressing effect of leptin and insulin. In addition, the dampening of brain mechanisms by palmitic acid may occur long before any other signs of obesity might be noticeable elsewhere in the body.

The Journal of Clinical Investigation, Vol. 119, No. 9, pp. 2577-2589, September 1, 2009 Free Full Text Study

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