“Beauty sleep” may have a legitimate meaning for teen girls concerned with their appearances.  In addition to feeling tired and cranky, teen girls who sleep less than recommended are at risk for putting on weight.  A recent study found that female teens who skimped on sleep had a different diet than their well-rested counterparts.

The study looked at 240 teens between 16 and 19 years-old. Of these teens, 18% were obese, but the average BMI was 23.1, which is considered normal weight.  Continuing with their normal lifestyle, teens wore a sleep watch to estimate how many hours they slept, focusing solely on sleep during the week, as weekend schedules tend to fluctuate. 2/3 of the teens slept an average of fewer than 8 hours per night.

The researchers also looked at the teens’ diet. What they discovered was that teen girls who slept fewer than 8 hours ate 3.3% more of their calories from fat, yet 3.8% less from carbohydrates than those who got a full night’s sleep. Additionally, teenage girls who slept less were four times more likely to consume over 475 calories daily from snacks compared to those who slept more. Among teenagers of both genders, those who slept less tended to eat food in the early morning, and tended to consume more of their daily calories at that time than those with more sleep.

This is bad news for teenage girls who skip sleep because although the difference in percentage of calories from fat is small, it can add up over time and cause weight gain. Fat has more than twice the calories as protein and carbohydrates.  Consequently, higher fat diets tend to result in increased caloric intake for the day. Furthermore, although the study didn’t specify what type of snacks the teens were eating, given what we know about the snacking habits of kids, it’s likely that they were largely unhealthy options like chips or sweets.

Experts propose a few reasons why sleep may alter eating habits and weight:

• hormone changes increase hunger
• less energy is used during the day because of fatigue
• extended wakeful periods allow for more time to eat

It should be stressed that this study only looked at the relationship between sleep and diet. Hence, it cannot conclude that sleeping fewer than eight hours definitely causes an increase in fat intake, snacking, or weight gain. Regardless, the importance of getting enough sleep is well documented, and teenage girls who want to feel – and look – their best should follow the experts’ recommendation to sleep for nine hours per night.