May 17, 2012
When You Eat Matters As Much As What You Eat
When you eat might be as important as what you eat when it comes to weight gain. That's the conclusion of a study reported in the Cell Press journal Cell Metabolism published online on May 17th.
A new study shows, when mice on a high-fat diet are restricted to eating for eight hours per day, they eat as much as those who eat around the clock, yet they are protected against obesity and other metabolic ills. The discovery proposes that the health effects of a poor diet may result in part from a mismatch between our eating schedules and our body clocks.
"Every organ has a clock," said lead author of the study Satchidananda Panda of the Salk Institute for Biological Studies. This means at times our livers, intestines, muscles, and other organs will work at peak efficiency and other times they are somewhat sleeping.
Those metabolic cycles are crucial for processing cholesterol breakdown to glucose production, and they should be primed to turn on when we eat and back off when we don't, or vice versa. When mice or people eat frequently throughout the day and night, it can throw off those normal metabolic cycles.
"When we eat randomly, those genes aren't on completely or off completely," Panda said. The principle is just like it is with sleep and waking, he explained. If we don't sleep well at night, we aren't fully awake during the day, so we work less efficiently as a consequence.
Panda's team fed mice either a standard or high-fat diet with one of two types of food access: ad lib feeding or restricted access. This experiment was done in order to find out whether restricted feeding alone–without a change in calorie intake–could prevent metabolic disease.
The time-restricted mice on a high-fat diet were protected from the adverse effects of a high-fat diet and showed improvements in their metabolic and physiological rhythms. They suffered less liver damage and gained less weight. The mice also had lower levels of inflammation, among other benefits.
Panda says "there is reason to think our eating patterns have changed in recent years, as many people have greater access to food and reasons to stay up into the night, even if just to watch TV. And when people are awake, they tend to snack".
The findings suggest that restricted meal times might be an underappreciated lifestyle change to help people keep off the pounds. At the very least, the new evidence suggests that this is a factor in the obesity epidemic that should be given more careful consideration.
"The focus has been on what people eat," Panda said. "We don't collect data on when people eat."