BOSTON — Sleep deprivation and frequent circadian misalignment are known risk factors for packing on the pounds. Now a small study presented here suggests that routinely eating meals late in the day or at night also increases obesity risk independent of how much sleep people get.
After controlling for sleep duration, the laboratory study involving healthy volunteers found that compared to eating during the daytime, prolonged eating that began at noon and went as late as 11 p.m. was associated with weight gain, increases in insulin and cholesterol levels, and impaired fat metabolism.
Results from the early research were presented early this week by Namni Goel, PhD, of the University of Pennsylvania Perelman School of Medicine at SLEEP 2017, the joint annual meeting of the American Academy of Sleep Medicine and the Sleep Research Society.
Goel explained that while sleep deprivation has been shown in numerous studies to be associated with weight gain, the metabolic consequences of routinely eating later during a 24-hour period are not well understood. Late-day or night eating is common among people who sleep erratic hours and/or are sleep deprived.
“In our study we wanted to compare the effects of delayed eating versus daytime eating in people who were not sleep deprived,” Goel told MedPage Today.
Eight healthy, normal-weight adults (age 26.25 ± 3.2; BMI 22.39 ± 1.9; four women) participated in the randomized cross-over study in free-living conditions with two phases: daytime eating (three meals and two snacks consumed between 8 a.m. and 7 p.m.) and delayed eating (three meals and two snacks consumed between noon and 11 p.m.)
The participants ate similar diets, and energy and macronutrient content were comparable between conditions. All participants slept, on average around seven hours each night during the study period, from 11 p.m. until 7 a.m. This was verified using actigraphy.
Exercises levels were also controlled, and were similar during both eating periods.
Study participants spend eight weeks on the first condition followed by a two-week washout period, followed by eight weeks on the second condition.
Weight, adiposity, energy metabolism, and hormonal markers were assessed at four points: baseline, after the first eating condition, after the washout period but before the second eating condition began, and after the second eating condition.
Preliminary analyses from the study indicate that delayed eating, compared to daytime eating, led to slight weight gain and increases in respiratory quotient. The findings also showed that eating later in the day is associated with metabolizing fewer lipids and more carbs, Goel said.
Insulin and cholesterol levels also were increased and adiponectin was decreased during the noon to 11 p.m. eating period.
Goel told MedPage Today that the study provides some of the first experimental evidence that prolonged delayed eating promotes weight gain and a negative profile for fuel oxidation, energy metabolism, and hormonal markers, in normal weight adults.
“These study subjects were not overweight. In fact, they were pretty thin, with average BMIs of around 22,” she said. ” So we would expect to see larger effects in obese people or people with metabolic syndrome.”
The study’s small size was an obvious limitation, but Goel said the fact that researchers were able to control for other factors associated with obesity and metabolic disturbance, such as sleep time, exercise, and food nutrient content, was a study strength.
Goel noted that a 24-hour hormonal profile showed that during the daytime eating period, the appetite hormone ghrelin peaked earlier in the day, while the satiety protein leptin peaked later, suggesting that eating earlier in the day helped the participants to stay satiated longer.
Melatonin levels remained constant during both eating periods, which would be expected given that sleeping routines were the same.
Goel acknowledged that larger studies and studies in people who are obese or have metabolic syndrome will be needed to confirm and expand on the findings.
“But this is a behavioral intervention that, I think, would be easy to implement in one’s own life,” she said. “Limiting eating to mostly daytime hours could be beneficial. Even if people can’t do it all of the time, most of us could do it 80% of the time. “
This research was funded by the National Institutes of Health.
Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner
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