That late-night pizza can affect not only your waistline but your overall health, according to a researcher at the University of Kentucky.
A series of powerful biological cues influence how and when you body works at peak efficiency, said Vincent Cassone, a University of Kentucky College of Arts and Sciences professor and chair of the biology department. He has published more than 100 papers in leading academic journals on the internal timekeeping functions of the body.
Most people are aware that there are universal biological cues that help set a body's clock to do certain things at certain times — such as sleep when it is dark — during the 24 hours in a day. These circadian rhythms have long been thought to be controlled through a collection of neurons in the hypothalamus known as the suprachiasmatic nucleus.
But Cassone said his research has shown that "the molecular mechanisms for clocks are distributed all over the body."
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"The gastrointestinal system itself is a biological clock," he said.
So why does that matter?
The body is biologically wired, for example, to restore and repair certain systems while resting, and rest is dictated by that 24-hour cycle. Cassone's research shows that environmental cues, such as eating late, can potentially disrupt that repair cycle and affect overall health.
Research has shown that people whose biological clocks are out of sync with their lifestyles — people who work night shifts, for example — have higher rates of some illnesses. People who eat at unusual times have more digestive illnesses than those who eat primarily during daytime hours, when the motility of the gastrointestinal system is at its peak — in other words, when your gut is working the most efficiently.
Even if someone is used to being up all night, the body isn't prepared to digest full meals at a time when biological cues indicate it should be at rest. There is a series of internal biological functions that must occur for the gastrointestinal system to prepare to digest a full meal, Cassone said.
If there could be a complete understanding of how those gut clocks work, he said, there is better hope for prevention and treatment of gastrointestinal diseases including colitis, Crohn's disease, colon cancer and irritable bowel syndrome. His current research, financed by a $1 million grant from the National Institutes of Health, is looking at the relationship between gastrointestinal clocks and aging.
Understanding the complicated biological cues is becoming increasingly important, he said, as American lifestyles shift to make all-night bingeing possible. (24-hour McDonald's anyone? Need a Dorito Taco after a multi-day World of Warcraft marathon?)
Cassone said researchers know that the body craves higher-fat food later in the day. Even the biologist is occasionally prone to giving in to that late-night pizza craving. But researchers still don't know exactly why, he said.
Until then, he said, it's probably best to follow the advice that might have come from your grandma. Eat your big meal in the morning to make things a little easier on your system, and refrain from heavy eating later in the day.