TOPLINE:
People who are obese burn calories in daily circadian cycles that are altered compared with those who are not obese, with the lowest point of energy expenditure occurring during their awake hours, as opposed to the typical lowest expenditures during sleeping hours observed among those of healthy weight.
Circadian patterns of glucose regulation are also altered among those who are obese, with key implications of the findings being potential clues in optimizing weight management approaches and reducing adverse effects of sleep regimens that counter the metabolic circadian patterns.
METHODOLOGY:
The study involved 30 volunteers in healthy and obese weight ranges, who took part in a rigorous circadian protocol involving designated times of being awake and asleep and eating throughout each day for 5 days.
Of the patients, 13 were of healthy weight (body mass index [BMI] > 25 kg/m2, and 17 were obese, defined as a BMI of 30 km/m2 or higher. They had a mean age of 48 and 14 were female.
In addition to receiving regular blood, glucose and insulin testing, the participants took part in exercises while being monitored with an indirect calorimeter, which measures levels of exhaled carbon dioxide and estimates energy expenditure.
After a baseline day of a normal sleep period, participants entered a "forced desynchrony" protocol to uncouple behaviors of sleep and wakefulness cycles from endogenous patterns in energy and glucose metabolism.
