Northwestern U. study: Late-night snacking disrupts ‘internal clock’

EVANSTON, Ill. – You might want to think twice about that midnight Pizza Express delivery. A Northwestern University study recently revealed that eating a high-fat diet disrupts the internal body clock of mice, causing them to eat when they should be resting.\n“It’s similar to waking in the middle of the night and raiding the refrigerator,” said Aaron Laposky, research assistant professor at the Center for Sleep and Circadian Biology and one of the study’s authors.\nThe study, published Wednesday in the medical journal “Cell Metabolism,” shows that overeating disrupts the body’s biological clock, throwing off the timing of sleep cycles and weakening appetite control. The biological clock is the control center for behavior and tissue function. It operates on a 24-hour cycle that governs bodily operations like sleeping and waking, fluid balance, body temperature and oxygen consumption.\nIn the study, 45 percent of the calories eaten by mice were from fat. For humans, nutritionists recommend that no more than 30 percent of calories come from fat. After just two weeks on the high-fat diet, the mice showed changes in the rhythms that control eating and sleeping – even before they gained weight.\nThis suggests that excess weight isn’t the only problem. A high-fat diet may cause changes at the molecular level, Laposky said. In the study, researchers observed changes in genes that encode the clock in the brain and fat tissues.\n“It’s not just the weight gain,” he said. “And even the mice who gained a little bit of weight showed the same behavior as obese mice.”\nThe excess calories eventually caused weight gain, further disrupting the mice’s internal clock. That in turn negatively affected metabolism and encouraged more ill-timed eating, perpetuating the cycle of weight gain. \nAnother experiment showed mice on the high-fat diet slept more and had poorer sleep quality than mice on a regular diet.\nThe study was inspired by a similar set of experiments by Northwestern researchers two years ago. That study showed that mice who already had abnormal sleep patterns became overweight. \nThis time, they hoped to see how high calorie intake affects the biological clock, said study leader Dr. Joe Bass, head of endocrinology and metabolism at Evanston Northwestern Healthcare and a professor at Northwestern’s Feinberg School of Medicine. \n“We found that the genes that control the clock also control appetite, which made us wonder if a high-fat diet could turn around and disrupt the clock,” Bass said.\nThe scientists don’t plan to do body clock research on people, but other studies with human subjects corroborate their theories, Laposky said. Studies have shown that obese people are sleepier during the day, and many with diabetes have abnormal body clocks, he said.\nPeople who work at night and eat at odd times of the day may have difficulty maintaining their weight because they have to fight the natural tendencies of their internal clock, Bass said. \n“Hunger and metabolism is carefully orchestrated by the body and comes in at specific times,” he said. “If you disrupt those times, that may cause abnormalities in the way the body processes sugar or fat.”