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Sex and race differences in caloric intake during sleep restriction in healthy adults

Abstract

Background: Evidence indicates that men and African Americans may be more susceptible to weight gain resulting from sleep loss than women and whites, respectively. Increased daily caloric intake is a major behavioral mechanism that underlies the relation between sleep loss and weight gain.

Objective: We sought to assess sex and race differences in caloric intake, macronutrient intake, and meal timing during sleep restriction.

Design: Forty-four healthy adults aged 21–50 y (mean ± SD: 32.7 ± 8.7 y; n = 21 women, n = 16 whites) completed an in-laboratory protocol that included 2 consecutive baseline nights [10 or 12 h time in bed (TIB)/night; 2200–0800 or 2200–1000] followed by 5 consecutive sleep-restriction nights (4 h TIB/night; 0400–0800). Caloric intake and meal-timing data were collected during the 2 d after baseline sleep and the first 3 d after sleep restriction.

Results: During sleep restriction, subjects increased daily caloric intake (P < 0.001) and fat intake (P = 0.024), including obtaining more calories from condiments, desserts, and salty snacks (Ps < 0.05) and consumed 532.6 ± 295.6 cal during late-night hours (2200–0359). Relative to women, men consumed more daily calories during baseline and sleep restriction, exhibited a greater increase in caloric intake during sleep restriction (d = 0.62), and consumed a higher percentage of daily calories during late-night hours (d = 0.78, Ps < 0.05). African Americans and whites did not significantly differ in daily caloric intake, increased caloric intake during sleep restriction, or meal timing. However, African Americans consumed more carbohydrates, less protein, and more caffeine-free soda and juice than whites did during the study (Ps < 0.05).

Conclusions: Men may be more susceptible to weight gain during sleep loss than women due to a larger increase in daily caloric intake, particularly during late-night hours. These findings are relevant to the promotion of public health awareness by highlighting nutritional risk factors and modifiable behaviors for weight gain related to sleep-wake timing.

Full-text

Alex’s Notes: Carl Lanore once said “if it disturbs your sleep it isn’t worth it.” Given the growing body of observational and clinical evidence suggesting sleep deprivation is a risk factor for obesity and metabolic disturbances, I believe Carl hit the nail on the head. A very recent study, for instance, found that reducing sleep time for a work week from eight to five hours led to weight-gain in healthy adults mainly as a result of increased calorie intake. Granted, provided that someone has control over their food intake, this increased snacking isn’t likely to occur. But for the general population, it is a problem. So purpose of the study at hand was to examine the effects of sleep restriction (SR) on healthy volunteers and how these effects differed with regard to sex and race.

The subjects were 44 healthy white and African American men and women with an average age of 33 years and average BMI of 25 (borderline overweight). All had a habitual sleep time of about eight hours and went to bed around 11:30pm, which in my opinion is still really late. They were confined to a laboratory for 14 consecutive days where they had two regular nights of sleep followed by five days of sleep restriction, and repeat. The restriction allowed for only four hours of sleep from 4-8am. Additionally,

“Subjects selected their meals and snacks by choosing from various menu options, selecting additional food and drink available in the kitchen within the laboratory suite (which included a refrigerator, microwave, and toaster oven), and making requests to the study staff. To ensure subjects were provided sufficient time to eat each day, three 30- to 45-min eating opportunities were specified in the protocol during days with a 2200 bedtime (0900, 1235, and 1830) and one additional 30-min opportunity to eat was specified in the protocol during days with a 0400 bedtime (0030). In addition to these specified meal times, subjects were allowed to consume food and drink at any time during the protocol other than when they were completing neurobehavioral tests or sleeping.”

In line with other studies, caloric intake was greater during SR, with men consuming more than women and no difference observed for race. To make comparisons easy, the researchers calculated the estimated energy requirements (EER) of the participants and looked at food intake as a percentage of this amount. With that in mind, SR led to a 24% increase over the calorie intake during the normal sleep schedule relative to EER. Moreover, SR led to less protein intake and greater fat intake on average, and African Americans consumed more carbohydrates and less protein than whites. In support of these calorie and macronutrient changes, it should not be surprising to learn that SR led to greater intakes of bread, cereal, rice, pasta, condiments, desserts, salty snacks, soda, and juice. Men consumed more breads and co. than women, and African Americans enjoyed more juice and soda than whites.

And all the above was thanks to snacking. During SR, the subjects consumed more calories from 3-10pm than during baseline, but the overall percentage of total calorie intake didn’t differ, suggesting that the increase there was no compensation for this increase in calorie intake during earlier hours. In other words, the subjects ate normally and then added an addition 530 kcal during SR. Relative to total calorie intake, there were no differences in sex or race.

Carbohydrates are used immediately for energy, so it is interesting that it was fat intake that increased with sleep deprivation. However, when looking at food groups it appears that the subjects favored the carbohydrate rich snacks, juices, and grains. More than likely is that the fat came as a by-product of making these energy sources more palatable, and the mind was seeking food that would reward it for working late into the night. Also, I must reaffirm and earlier statement. This study cannot be applied to the physical culturist who controls his/her food intake. However, the average population doesn’t have this self-control, and thus managing sleep is crucial for both weight-loss and improved decision making.

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