"This study confirms several studies reporting that weight loss is associated with increased sleep duration," said the study's lead investigator, Nasreen Alfaris, MD, MPH, a fellow in the Department of Medicine at the Perelman School of Medicine at the University of Pennsylvania, Philadelphia.
In addition, the study found that weight loss at 6 months improved sleep quality, as well as mood, regardless of how the individuals lost the weight.
The 390 study subjects participated in the Practice-Based Opportunities for Weight Reduction at the University of Pennsylvania (POWER-UP) trial. This 2-year study, funded by the National Institutes of Health, compared three behavioral interventions for weight loss in obese adults treated in primary care practices.
Subjects (311 women and 79 men) were randomly assigned to one of three programs that provided varying amounts of support to achieve the same diet and exercise goals. The groups were: (1) usual care, in which subjects received printed educational materials during quarterly visits with their primary care provider; (2) brief lifestyle counseling, which included quarterly visits with their primary care provider, combined with brief meetings with lifestyle coaches; or (3) enhanced brief lifestyle counseling, with meal replacements or weight loss medications added to the second intervention.
The researchers evaluated changes in weight, sleep duration and quality, and mood after 6 and 24 months of treatment. They compared subjects who lost 5 percent or more of their original body weight with those who lost less than 5 percent, regardless of their group assignment. The analyses controlled for several subject variables, including sex and age.
At month 6, subjects in both lifestyle counseling groups lost more weight on average (brief counseling: 7.8 lb; enhanced counseling: 14.7 lb) than those in the usual care group (4.4 lb), Alfaris reported.
Examining all three groups together, subjects who lost at least 5 percent of their weight at month 6 reported that they gained an average of 21.6 minutes of sleep a night, compared with only 1.2 minutes for those who lost less than 5 percent. Likewise, subjects who lost >5% of initial weight reported greater improvements on measures of sleep quality and mood (i.e., symptoms of depression), compared with subjects who lost <5%.
Only improvements in mood remained statistically significant at 24 months, according to Alfaris.
"Further studies are needed to examine the potential effects of weight regain in diminishing the short-term improvements of weight loss on sleep duration and sleep quality," she said.