Elevated ghrelin predicts food intake during experimental sleep restriction

Abstract

Objective: Sleep curtailment has been linked to obesity, but underlying mechanisms remain to be elucidated. This study assessed whether sleep restriction alters 24-h profiles of appetite-regulating hormones ghrelin, leptin, and pancreatic polypeptide during a standardized diet and whether these hormonal alterations predict food intake during ad libitum feeding.

Methods: Nineteen healthy, lean men were studied under normal sleep and sleep restriction in a randomized crossover design. Blood samples were collected for 24 h during standardized meals. Subsequently, participants had an ad libitum feeding opportunity (buffet meals and snacks) and caloric intake was measured.

Results: Ghrelin levels were increased after sleep restriction as compared with normal sleep (P < 0.01). Overall, sleep restriction did not alter leptin or pancreatic polypeptide profiles. Sleep restriction was associated with an increase in total calories from snacks by 328 ± 140 kcal (P = 0.03), primarily from carbohydrates (P = 0.02). The increase in evening ghrelin during sleep restriction was correlated with higher consumption of calories from sweets (r = 0.48, P = 0.04).

Conclusions: Sleep restriction as compared with normal sleep significantly increases ghrelin levels. The increase in ghrelin is associated with higher consumption of calories. Elevated ghrelin may be a mechanism by which sleep loss leads to increased food intake and the development of obesity.

Figure 1

Twenty-four hour profiles of (A) ghrelin, (B) leptin and (C) pancreatic polypeptide under normal sleep (black lines) and sleep restriction (red lines). Horizontal black bars indicate time in bed under normal sleep (2300h to 0730h) and red bars indicate time in bed under sleep restriction (0100h to 0530h). Black arrows represent identical meals served at 0900h, 1400h and 1900h. Data are shown as mean ± SEM.

Figure 2

Postprandial ghrelin responses to breakfast, lunch and dinner meals under normal sleep (black bars) and sleep restriction (red bars). The AUCs were calculated during the 2.5 hours after each meal using the trapezoidal method. Identical meals were served at 0900h, 1400h and 1900h. Data are shown as mean ± SEM.

Figure 3

Caloric intake during the ad libitum feeding period under normal sleep (black bars) and sleep restriction (red bars). (A) Total caloric intake, (B) carbohydrate intake, (C) fat intake, (D) protein intake. The ad libitum feeding opportunity included buffet meals (lunch buffet served at 1500h and dinner buffet served at 1930h) and unlimited access to a snack bar between the two buffet meals. Data are shown as mean ± SEM.

Figure 4

Correlation between the change in evening ghrelin levels (i.e. dinner-related peak) and the change in caloric intake from sweet snacks. Change values are expressed as the difference between sleep restriction and normal sleep.

Figure 5

Total activity counts from the (A) waist monitor and (B) wrist monitor under normal sleep (black bars) and sleep restriction (red bars). Data are shown as mean ± SEM. Data are from n=16 for the waist monitor and n=18 for the wrist monitor.