Eat Late, Gain Weight?

I’ve always heard that you shouldn’t eat after a certain time at night. The time varies by expert, but it’s always the same idea: Eat Late, Gain Weight!

But with no hard evidence, I convinced myself it was just one of many diet myths perpetuated to prevent me from enjoying my low-cal ice cream in the evening.

Shouldn’t calories in vs. calories out be all that matters?

Contrary to my wishful thinking, that isn’t the case. New scientific evidence actually supports the “no late night snacking” rule.

I spoke with Dr. Laura Fonken of Ohio State University, who did a study recently on the eating patterns of three groups of mice, to get to the bottom of this issue.

Here's how her study went:

The first group of mice was exposed to 16 hours of light and 8 hours of darkness (a normal sleep cycle). The second had light 24/7. The third had 16 hours of light, and 8 hours of dim light (comparable to sleeping with a T.V. on).

The researchers found that although all the mice ate the same amount of food and had the same activity level, the 2nd and 3rd group gained 50% more weight than the mice on the normal light cycle.

What made the difference between the groups?

Fonken believed it was because the mice in groups 2 and 3 ate almost half of their calories at night, during "normal sleeping hours." This was because with the lights on, they had no concept of day/night and just ate, slept, and moved about as they pleased.

To test this, she repeated the study with the same light/dark groups but restricted eating periods to only daytime hours. Dr. Fonken found that when the mice ate all of their calories during the "daytime," none of the groups gained weight.

They also experimented with the first "normal" group, only allowing them access to the food during the 8 hour dark period. When that disruption occurred, the group then gained weight, just like groups 2 and 3 in the first test (even though they ate the same amount of calories).

So what does this prove?

"We believe these results demonstrate how modern societal developments can impact health," says Fonken. "Electrical lighting allowed for the extension of daytime activities into the night; in many ways our society now functions on a 24 hour a day schedule. These results suggest that such a schedule may impact metabolic function."

Fonken says they haven't determined why exactly eating at night caused the weight gain, but they do know that it had nothing to do with the amount of food, amount of light, or amount of sleep/activity, because it was the same among all groups.

They only thing that mattered was when the mice ate.

And other evidence supports this theory.

"There have been studies that have shown that night shift workers have increased BMI and increased risk for cardiovascular disease as compared to day shift workers," says Fonken. "A subset of patients with night-eating syndrome are obese and show a persistent pattern of late night binge eating. Furthermore, studies in college students have shown that brief disruptions in feeding schedules can alter metabolic parameters."

So should you skip dessert from now on?

Although Fonken was careful to clarify that her experiment only applied to mice, I think this test just adds to the mounting evidence that stuffing your face at night is a no-no. While the occasional dessert probably won't ruin your waistline, I would encourage you to finish your dinner before Dancing with the Stars!