Caloric Restriction, the Menstrual Cycle, and Sleep in Women Without Obesity.

IntroductionShort-term caloric restriction is a common practice even in lean and underweight women. We studied the impact of dietary restriction on sleep and its interplay with reproductive hormones across the menstrual cycle in women without obesity.MethodsSeventeen healthy women without obesity, aged 23.6 ± 2.3 years (mean ± SD) underwent a neutral (± 0%) and deficient energy availability diet (-55%) in the early follicular phase of 2 menstrual cycles. Actigraphic data and urinary LH, estrone-3-glucuronide (E1G), and pregnanediol-3-glucuronide (PDG) were collected daily. Blood orexin and leptin were collected on the fifth day of each diet. Sleep was analyzed in relation to menstrual cycle phase, diet, and hormones.ResultsDecreased energy availability and menstrual cycle phase independently affected wake after sleep onset (WASO; P = .004, P = .007 for diet and cycle phase, respectively) and number of awakenings (NOA; P = .03, P = .0006, respectively) with the greatest sleep disruption in the late luteal phase. Sleep efficiency (SE) was lower and duration of awakenings was longer in association with dietary restriction. Orexin was positively associated with WASO (P = .02), the sleep fragmentation index (P = .001), and NOA (P = .009) and inversely related to SE (P = .02). Increasing PDG was associated with WASO (P < .05) and duration of awakenings (P < .05) and inversely associated with SE (P < .01). Increasing E1G was positively associated with WASO (P < .05) and NOA (P < .01).ConclusionShort-term modest caloric restriction independently disrupts sleep and exacerbates changes in sleep that occur across the menstrual cycle in healthy, young women without obesity.