A study conducted by the University of Pennsylvania’s sleep laboratory, run out of their Unit for Experimental Psychiatry, Division of Sleep and Chronobiology, has confirmed what a lot of us knew in our heart of hearts - that the later we’re staying up and the less sleep we’re getting, the more we are eating. And we’re not eating healthy foods either; we’re making unhealthy choices that are loaded in fat. The Penn researchers had their suspicions based on studies by other scientists that had previously linked short sleep to weight gain and obesity, but their study went beyond any other because of the high number of participants they were able to track through their busy lab, and their reports were surprising in the degree to which they confirmed what the other studies had indicated. Their findings revealed that people whose sleep had been restricted for five nights in a row gained two pounds, while those who had been allowed to sleep for ten hours during that same period gained only a quarter of a pound. Researchers followed 225 subjects, all of whom were of normal weight, healthy and between the ages of 22 and 50. All spent consecutive days in the sleep lab, with some assigned a ten-hour sleep period and the others subjected to sleep deprivation of only four hours per night. Everybody had the same established meals and all had the opportunity to help themselves to snacks that were made easily available. None were allowed to exercise. In addition to the two pound weight gain seen in the subjects who were sleep deprived, the same group that gained were seen to have been taking in a larger percentage of their calories from fat, and were also seen to have been eating late at night. It was important to be able to show this as a comparison to a group that were also in the sleep lab, as it counters any theory that the increased eating at night and higher caloric intake was caused by having been in the lab. An analysis of the nutritional makeup of the food that the sleep deprived subjects took in did not show a higher percentage of carbohydrates, though many researchers had expected that it would. Instead, the results showed that they remained at a balanced proportion of nutritional macronutrients. Similar studies have been done over the years, and have yielded supporting or complementary results. In one study out of the University of Colorado Denver’s Anschultz Medical campus, sleep researchers detected a marked increase in after dinner snack eating in subjects who were sleep deprived at a level of fewer than five hours of sleep per night for a period of a week. A separate study conducted by The Endocrine Society linked sleep deprivation to an elevated level of a blood molecule that makes us feel good when we eat. Whichever study you choose to use as your guide, it seems obvious that one secret to controlling your weight is a good night’s sleep.