title: Endocrine responses to nocturnal eating--possible implications for night work.
abstract: BACKGROUND
  Night work is becoming more common and shift workers display several metabolic disturbances. Aim To study the endocrine responses in relation to time of day during a 24-h period and how dietary macronutrient composition affects these responses.
  
  
  METHODS
  Seven males (26-43 y and 19.9-26.6 kg. m(-2)) were studied in a crossover design. Isocaloric diets described as high-carbohydrates (HC; 65 energy percent (E%) carbohydrates and 20E% fat) or high-fat (HF; 40E% carbohydrates and 45E% fat) were given. After a 6-day diet adjustment period, the subjects were kept awake for 24 h in a metabolic unit and were served an isocaloric meal (continuation of respective diet) every 4-h. Blood samples were taken throughout the 24-h period.
  
  
  RESULTS
  Insulin and leptin responses to meal intake differed with respect to time of day (p < 0.05). Time of day affected glucagon, thyroid stimulating hormone (TSH), free thyroxin (fT4), total triiodothyronine (tT3), cortisol, chromogranin A (CgA) and pancreatic polypeptide (PP) concentrations (p < 0.05). Meal intake decreased cortisol concentration after meals at 0800, 1200 and 0400 but not at 1600, 2000 and 0000 h. The PP's postprandial increase was greater during 0800-1600 h compared to 2000-0800 h. With the HC meals, lower glucagon and CgA concentrations (p < 0.05), and a tendency for lower tT3 concentrations (p = 0.053) were observed compared to the HF meals.
  
  
  CONCLUSIONS
  Insulin, PP, TSH, fT4, cortisol and leptin responses to meal intake differed with respect to time of day. The decreased evening/nocturnal responses of cortisol and PP to meal intake indicate that nocturnal eating and night work might have health implications.
authors.affiliation: Department of Medical Sciences, Clinical Chemistry, Uppsala University Hospital, 751 85 Uppsala, Sweden. ulf.holmback@medsci.uu.se
authors.forename: Ulf
authors.initials: U
authors.lastname: Holmbäck
authors.forename: Anders
authors.initials: A
authors.lastname: Forslund
authors.forename: Arne
authors.initials: A
authors.lastname: Lowden
authors.forename: Jeanette
authors.initials: J
authors.lastname: Forslund
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Akerstedt
authors.forename: Maria
authors.initials: M
authors.lastname: Lennernäs
authors.forename: Leif
authors.initials: L
authors.lastname: Hambraeus
authors.forename: Mats
authors.initials: M
authors.lastname: Stridsberg
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002940:Circadian Rhythm / Q000502:physiology*; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000378:metabolism; D004041:Dietary Fats / Q000378:metabolism; D005247:Feeding Behavior / Q000502:physiology*; D006728:Hormones / Q000097:blood*; D006801:Humans; D008297:Male; D009490:Neurosecretory Systems / Q000502:physiology*; D013997:Time Factors; D014940:Work Schedule Tolerance / Q000502:physiology*
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D006728:Hormones