High-fat diet disrupts body clock -study

By Julie Steenhuysen

CHICAGO, Nov 6 (Reuters) - Eating just a few meals loaded with fat -- think holiday food -- could be enough to throw off the body's internal clock, starting a vicious cycle that could lead to obesity and diabetes, U.S. researchers said on Tuesday.

They found mice fed high-fat foods showed marked changes in their diet and sleep patterns, sleeping longer and eating when they should be sleeping.

"The effect can be seen quite rapidly -- within a matter of days," said Dr. Joe Bass of Northwestern University and Evanston Northwestern Healthcare in Illinois, whose study was published in the journal Cell Metabolism.

He said the study suggests overeating alters a core mechanism of the body clock, disrupting the timing of internal signals like appetite control.

"What we saw is that the ticking of the clock slowed down," Bass said in a telephone interview.

Known as the circadian clock, this internal time keeper manages the body's daily rhythms, regulating when to sleep, wake, eat and many other functions of the body.

Prior studies led by Bass found that a faulty body clock can raise the risk of obesity and diabetes. Bass' latest study shows that overeating can trigger this process.

But the effect may not be automatic. Humans have been shown in many studies to have more complex reactions to changes in diet than mice do.

For this study, Bass and his team worked with two groups of genetically similar mice. They all ate a regular diet the first two weeks. Then half of the mice stayed on the regular diet and half went on a high-fat regime, in which 45 percent of calories came from fat.

The study took place in total darkness to prevent any external cues for guiding the animals.

After two weeks, mice on this high fat-fare began to change, eating and resting at inappropriate times. Mice on the normal diet did not.

"If you give a mouse a high-fat diet, they will eat excessive amounts," Bass said. "It is the same thing as human eating at McDonald's or eating too much at a Thanksgiving dinner."

Bass said the diet changed the underlying genetic mechanism of the internal clock.

"What we found was the expression of the genes that encode the clock is altered under high-fat diets. It is as if the diet erodes away the clock or causes it to rust," Bass said. "It erodes the abundance of the proteins in the cells."