A high-fat diet quickly causes changes to the body's internal clock, which can throw off appetite regulation, according to a new study conducted by researchers at Northwestern University and Evanston Northwestern Healthcare in Illinois. Published in the journal Cell Metabolism, the study was funded by the National Institutes of Health and by grants from Amylin Pharmaceuticals and Eli Lilly and Co.
"The effect can be seen quite rapidly - within a matter of days," lead researcher Joe Bass said.
Researchers conducted the study on two separate groups of mice that were kept in total darkness. Both groups were fed a normal diet for two weeks. Then one group continued with the normal diet, while the other mice were placed on a high-fat diet in which 45 percent of their calories came from fat.
The mice were kept in darkness to prevent light levels and other external cues from being able to act as regulators on their internal clocks.
Known as a circadian clock, the body's internal time regulator is responsible for sending out time-related signals such as hunger, sleepiness and wakefulness. Prior studies have indicated that a poorly regulated circadian clock is associated with an increased risk of obesity and diabetes.
The researchers found that mice on the high-fat diet began to eat and rest at inappropriate times relative to the mice in the control group. These changes took place after only two weeks. These changes appeared to be related to modifications in the expression of the genes that regulate the circadian clock.
"What we found was the expression of the genes that encode the clock is altered under high-fat diets," Bass said. "It is as if the diet erodes away the clock or causes it to rust. It erodes the abundance of the proteins in the cells."
"If you give a mouse a high-fat diet, they will eat excessive amounts," he said. "It is the same thing as human eating at McDonald's or eating too much at a Thanksgiving dinner."