High fat diets throw body clock out of sync

Nov 7 2007

Scientists say a diet high in fat can throw the body's internal clock 'out of sync'.

They say just a few meals which have a high fat content are enough to disrupt the body's internal clock initiating a vicious cycle that can lead to obesity and diabetes.

The researchers from the Northwestern University and Evanston Northwestern Healthcare in Illinois, suggest that overeating alters the core mechanism of the body clock and disrupts the timing of internal signals such as appetite control.

They say this shifting in the timing of the body’s internal clock happens within a matter of days.

The body’s internal clock is known as the circadian clock and is an internal time keeper which manages the body's daily rhythms, regulating when to sleep, wake, eat as well as many other functions of the body.

The circadian clock is an ancient mechanism for matching behavior to changes in the external environment which vary in accordance with the rotation of the earth, and the cycle of light and darkness.

Other research by Dr. Joe Bass has also found that a faulty body clock can raise the risk of obesity and diabetes but this most recent study shows that overeating can trigger this process.

For the study the researchers used two groups of genetically similar mice; for two weeks all ate a regular diet, then while half of the mice continued with this diet the other half were fed a high-fat diet in which 45 percent of their calories came from fat.

In order to prevent any external cues for guiding the animals, the study was conducted in darkness and it was found that within two weeks, the mice on the high fat diet began to change their habits and were eating and resting at inappropriate times.

The mice on the normal diet did not behave in this way.

The researchers saw that mice fed a fatty diet quickly develop changes in their normal activity patterns and begin eating more during the day, when mice who are nocturnal should be asleep.

The researchers also noticed changes in the molecular components of the circadian clock and in important aspects of metabolic chemistry.

Dr. Bass says they found that an animal on a high-fat diet gains weight, eats at the inappropriate time for its sleep/wake cycle and also all of the excess calories are consumed when the animal should be resting.

He says this equates to a human raiding the refrigerator in the middle of the night and bingeing on junk food.

Bass says these clock-controlled metabolic genes are expressed in parts of the brain, as well as in the liver and fat tissue and the high-fat diet suppressed the activity of the core clock genes.

He says not only is activity and feeding shifted, but the molecular processes involved in metabolism is also changed.

The study suggests timing and metabolism are closely linked, and disturbing this balance can have negative effects.

The research was funded by the National Institutes of health and grants from Amylin Pharmaceuticals and Eli Lilly and Co.

The study is published in the current issue of Cell Metabolism, a publication of Cell Press.