The 12 Hour Feeding Window

You probably understand that late night snacking is bad for you, but do you know why? Well, there are several reasons. For one, the food choices that people make late at night don't tend to the healthiest. Additionally, our bodies won't be able to make very much use of the extra calories before we go to bed, which means that the extra calories are more likely to be stored as fat. What I want to focus on today, however, is how eating late at night affects our inner clock, or circadian rhythm. 

Researchers at the Salk Institute for Biological Studies in San Diego have discovered that restricting when mice eat to only 12 hours or less per day staved off weight gain and illness - even if their diet was sometimes unhealthy. Though these studies have been conducted with only mice, Dr. Satchin Panda says the results seem likely to apply to humans.

These researchers fed groups of adult male mice one of four diets: high-fat, high-fructose, high-fat plus high-sucrose, and regular mouse food. Some of the mice in each dietary group were allowed to eat whenever they wanted throughout their waking hours; others were restricted to feeding periods of nine, 12 or 15 hours. The caloric intake for all the mice was the same.

Over the course of the 38-week experiment, some of the mice in the time-restricted groups were allowed to cheat on weekends and eat whenever they chose. A few of the eat-anytime mice were shifted to the restricted windows midway through the study.

By the end, the mice eating at all hours were generally obese and metabolically ill, reproducing the results of the earlier study. But those mice that ate within a nine- or 12-hour window remained sleek and healthy, even if they cheated occasionally on weekends. What's more, mice that were switched out of an eat-anytime schedule lost some of the weight they had gained.

Dr. Panda and his colleagues believe that the time at which food is eaten influences a body's internal clock, much like dark and light cycles. And circadian rhythm in turn affects the function of many genes in the body that are known to involve metabolism.

The final take away is this: from your first sip of coffee in the morning to your last bite of food in the evening, try to restrict when you eat to 12 hours a day or less and see what type of results you get. Anything besides water counts!

Want to learn more? I highly recommend listening to the following podcast: Satchin Panda, Ph.D. on Time-Restricted Feeding and Its Effects on Obesity, Muscle Mass & Heart Health

Roxy Turner 
BHC Nutrition Coach