Eating Time May Influence Weight Gain

late night snack donut fridgeWhen humans first started to walk the planet, food was pretty scarce. We often went for long periods of time without a big meal, and even when food was plentiful it had to be conserved and eaten judiciously. This stands in stark contrast to today’s world of refrigerated food, drive-thru eating and 24-hour grocery stores. Food is always at our fingertips, and for many of us, that means eating that starts soon after we wake up and finishes just before we go to bed (and sometimes after). This dramatic change in our eating habits pushed a group of researchers to wonder whether our all-day eating habits might also be partly responsible for the recent boom in obesity.

In a new study out this week, these researchers dove into the question of whether restricting your hours of eating might influence your overall weight. They tested several different situations to see how restricting the hours of eating might change weight gain. To start, they took two groups of mice and put one on a high-fat, high-sugar diet and allowed them access to food whenever they wanted. They took another group and fed them the same diet, but only gave them food access for nine hours a day. The mice ate the same amount, but the time they had to eat differed. When they weighed the mice, they found that those with unlimited access gained more weight than those with restricted access even though they ate the same number of calories.

They then asked whether the length of restriction mattered. They allowed mice either unlimited access to food or access only for 9, 12 or 15 hours. Again, all mice ate the same number of calories. But when they were weighed, weight gain followed the number of hours eating was restricted. Those with only nine hours to eat gained the least, then those with 12 hours, then 15 and then unlimited access.

Intrigued, the researchers tried applying the principle to a more typical human situation of being good all week but pigging out on the weekends. They found that mice who were switched from restricted access during the week to unlimited access on the weekend again gained significantly less than those who had constant food access throughout the week.

The big question was whether this finding might help those already overweight looking to lose. To find out, the research team switched some of the mice with unrestrained eating to a restricted diet after several months to see how their weight would change. Those mice switched saw a modest amount of weight loss soon after the switch that they then maintained for the rest of the study. This was compared to their counterparts who stayed on the unrestricted diet and continued to gain weight in spite of eating the same amount.

As with any study done in mice, these results may not translate into humans. While the bodies of mice are similar in many ways to our own, there are important differences. Yet the results of the study are encouraging. The researchers point out that many weight-loss programs available today require major changes in a person’s life. This study shows that a person could lose some weight just by shortening the hours they eat every day even if they continue to eat the same amount. While the weight loss wouldn’t be huge, it would be enough to have positive health effects. This research provides a possible small step as part of a larger program that could help establish lasting weight loss.