High-fat diet can throw off the body’s 24-hour internal clock

November 14th, 2007 - 8:37 am ICT by admin  
The circadian clock regulates sleeping, waking, eating, as well as the daily rhythms of many metabolic functions.

Now, for the first time, a Northwestern University and Evanston Northwestern Healthcare (ENH) study has shown that overeating alters the core mechanism of the body clock, shaking off the timing of internal signals, including appetite control, critical for good health.

The team found that mice fed a high-fat diet gained weight and showed a sudden disruption in their circadian clock, eating extra calories when they should have been sleeping or resting.

The team also found that a high-fat diet caused changes in genes that encode the circadian clock in the brain and in peripheral tissues (such as fat), resulting in reduced expression of these genes.

The study also showed that changes in metabolic state associated with obesity and diabetes not only affected the circadian rhythms of behaviour but also of physiology.

“Our study was simple — to determine if food itself can alter the clock. The answer is yes, alterations in feeding affect timing,” senior author Dr. Joe Bass, assistant professor of medicine and neurobiology and physiology at Northwestern and head of the division of endocrinology and metabolism at ENH, said.

“We found that as an animal on a high-fat diet gains weight it eats at the inappropriate time for its sleep/wake cycle — all of the excess calories are consumed when the animal should be resting. For a human, that would be like raiding the refrigerator in the middle of the night and binging on junk food,” he added.

The clock-metabolism cycles feed on each other, creating a vicious loop, says Bass. Once weight gain starts, the clock is disrupted, and a disrupted clock exacerbates the original problem, affecting metabolism negatively and increasing the propensity for obesity and diabetes.

“Timing and metabolism evolved together and are almost a conjoined system. If we perturb the delicate balance between the two, we see deleterious effects,” he said.

In their study, Bass and his team studied mice with the same genetic backgrounds. After feeding them a regular diet for two weeks, they were split into two groups for the remaining six weeks, one kept on a regular diet and the other fed a high-fat diet.

After two weeks, those on the high-fat diet showed a spontaneous shift in their normal pattern of activity/eating and resting/sleeping. They began to eat during their typical rest or sleep period (daylight for a mouse). The animals on a regular diet did not exhibit this behaviour.

“It’s not just that the animals are eating more at regular meals. What’s happened is that they actually shift their eating habits so that all excess food intake occurs during their normal rest period,” he said.

The study is published in the Nov. 7 issue of the journal Cell Metabolism. (ANI)

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