title: Leptin levels decline steadily during prolonged fasting in lean children.
abstract: OBJECTIVE
  To evaluate the effects of fasting on serum leptin levels in lean children.
  
  
  METHODS
  Seventeen children, age 7.7 +/- 4.3 years with mean body mass index (BMI) of 16.7 +/- 2.7 kg/m(2), underwent standard diagnostic fasts for suspected hypoglycemia. Blood was sampled at 6-hour intervals for glucose, insulin, C-peptide, leptin, free and total insulin-like growth factor-1, insulin-like growth factor-binding protein-1, growth hormone, cortisol, ketones, and free fatty acids.
  
  
  RESULTS
  Subjects fasted 15 to 40 hours, and initial leptin levels were related to BMI and age. Leptin declined by 0.5 ng/mL per each fasting hour (P = .008), using a longitudinal mixed effects model. Leptin dropped significantly from an initial mean +/- SEM during the first 6 hours of 15.9 +/- 5.5 ng/mL to 3.5 +/- 0.9 ng/mL at the end of fasting. Mixed longitudinal effects models demonstrated that leptin was significantly related to insulin over time (P < .0001) as well as C-peptide (P < .0001). Significant relations were also seen with total insulin-like growth factor-1 over time, beta-hydroxybutyrate and insulin, and insulin-like growth factor-binding protein-1 and insulin.
  
  
  CONCLUSIONS
  After 6 hours, leptin levels steadily decline during prolonged fasting in lean children. The decline probably is related to the suppression of insulin secretion. Although baseline leptin levels were related to BMI and age, in the final fasting sample, leptin levels showed minimal variation in this pediatric cohort encompassing a wide age range.
authors.affiliation: Division of Endocrinology and the Division of Biostatistics and Epidemiology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA. katzl@email.chop.edu
authors.forename: Lorraine E
authors.initials: LE
authors.lastname: Levitt Katz
authors.forename: Máire
authors.initials: M
authors.lastname: Abraham
authors.forename: Line
authors.initials: L
authors.lastname: Johansen
authors.forename: Abbas F
authors.initials: AF
authors.lastname: Jawad
mesh_terms: D015992:Body Mass Index; D002648:Child; D005215:Fasting / Q000097:blood*; D005260:Female; D006801:Humans; D020738:Leptin / Q000097:blood*; D008297:Male; D013997:Time Factors
chemical_list: D020738:Leptin