Teens who need to lose weight should quit staying up so late

Obese teens who diet to lose weight may have more success if they also focus on getting enough rest, a small study suggests.

“Sleep deprivation may be associated with increased caloric intake, and decreased physical activity, resulting in obesity,” said senior study author Dr. Juan Manuel Malacara of the University of Guanajuato in Leon, Mexico.

To see if extra sleep might make it easier to lose weight, researchers asked 52 obese teens to eat 500 fewer calories per day than usual. Then, they chose 25 teens at random to follow a personalized sleep plan designed to help them get up to an extra hour of rest at night, while the other 27 kept to their usual sleep routines.

After four weeks, teens on sleep plans increased their average sleep time by about 1.2 hours a night and lost an average of 2.1 kilograms (4.6 pounds). Without the sleep plans, teens only increased their sleep by about a half hour, on average, and they only lost an average of 1.2 kg (2.6 lb).

The results suggest that promoting extra sleep may help dieters succeed with weight loss, Malacara said by email.

“Sleep can influence the secretion of hormones that regulate appetite, (reducing) craving for food and (making people) more likely to be successful in cutting calories,” said Tianyi Huang of Brigham and Women’s Hospital and Harvard Medical School in Boston.

“More sleep will make people feel less sleepy or fatigued during the day, then people are more likely to work out more, leading to higher energy expenditure, which is good for weight loss,” Huang, who wasn’t involved in the study, said by email. “Sufficient sleep can also reduce stress, which is known to favor weight gain.” Beyond its small size, another limitation of the study is that researchers didn’t follow the youth for longer to determine whether sleep might impact their odds of achieving sustainable weight loss. Researchers also relied on teens to report sleep time in diaries and didn’t objectively measure how much they slept.

The study also didn’t look at exercise, or at what teens ate.

In theory, however, better-rested adolescents might be more conscious about choosing healthier foods and less likely to succumb to the temptation of high-calorie, high-carb sweets and junk foods, said Anna Rangan of the University of Sydney in Australia.

“Shorter sleep duration increases the time available for eating, especially in the evening where sedentary activities, such as watching television, and snacking on highly palatable and energy-dense foods are common,” Rangan, who wasn’t involved in the study, said by email.

Parents may need to encourage teens to change their evening routines, said Kristen Knutson, a researcher at Northwestern University in Chicago who wasn’t involved in the study.

“One way to improve the sleep of teens is to avoid bright light at night, particularly right before bedtime,” Knutson said by email. “This includes light from smart phones and tablets - although getting teens to put these away at night may be challenging.” The effort is worth it, though, to avoid poor sleep becoming a lifelong problem, said Stacey Simon of the University of Colorado Anschutz Medical Campus and Children’s Hospital Colorado in Aurora.

“Health habits learned in adolescence often continue into adulthood, so learning good sleep and eating strategies in adolescence is critical,” Simon, who wasn’t involved in the study, said by email.

The longer teens experience obesity, the greater the risk of future health problems such as cardiovascular disease and type 2 diabetes, Simon added.