The participants were all nurses who volunteered in a heart health program at the Medical Center; they received information about stress management, exercise, sleep, and nutrition. For the study, led by Arn Eliasson, participants wore actigraphy armbands, which tracked several body measures, including position, temperature, and total time spent being active and at rest. The researchers divided participants into two groups based on quality of sleep – “short sleepers” vs. “long sleepers” – and found that the average body mass index (BMI) of the “short sleeper” group was 28.3, but for the “long sleeper” group it was 24.5.
Researchers also found that heavier participants were also burning significantly more calories per day than the slimmer ones – an average of 1,000 calories per day more.
But that wasn’t the only exciting finding, nor was it the most surprising. The researchers also found that heavier participants were also burning significantly more calories per day than the slimmer ones – an average of 1,000 calories per day more. Why is this? The heavier nurses were actually more active, taking about 25% more steps per day than the lighter nurses (14,000 versus 11,300 steps).
The team isn’t sure of the mechanism behind these results, but Eliasson suggests some possibilities. One is that the normal flux of the hormone leptin is being disrupted by poor sleep; leptin controls satiety, so if its levels are off kilter, this might cause an individual to eat too much. Another possibility is that the nurses who slept less were simply more stressed out, which might lead to weight gain from overeating or stress eating. Or it may be that lack of sleep and associated stress cause individuals to be less organized, and expend more energy to accomplish the same amount of work.
Eliasson says that it “would be fascinating to know the results of a carefully designed study that controlled for the many influences on weight gain, while varying sleep parameters and measuring hormonal mediators of appetite and metabolism. We are planning further studies to evaluate the role of stress in sleep and metabolism.”