Study: The later you stay up, the more you eat

Research over the years has produced similar findings, but the new Penn study is significant because it used 225 people. And because the research took place in a lab, scientists were able to control for a variety of factors.

Andrea Spaeth, a doctoral candidate and the study’s lead author, called the logistics “a nightmare” but worthwhile because it increased the power of the results.

Spaeth said participants in the study could eat almost whenever they wanted and as much as they wanted. Meal sizes did not differ between baseline days and the five experimental days, or between the sleep-deprived group and a small control group. “But [the deprived group] ate more times through the day and shifted their calorie intake toward late night,” she explained. “The next morning they’d actually eat less.”

African-Americans were especially vulnerable to the effects of sleep deprivation. African-American men gained the most weight (about 1.7 kilos or 3.7 pounds), followed by African-American females and white men (both just under 1 kilo or 2.2 pounds), and white women (almost one-third kilo or .7 pounds).