title: Exercise addiction in men is associated with lower fat-adjusted leptin levels.
abstract: OBJECTIVE
  To test a hypothesized association between resting leptin levels (adjusted for body fat percentage) and symptoms of primary exercise addiction.
  
  
  METHODS
  Cross-sectional design.
  
  
  METHODS
  Habitual amateur exercisers participating in running, fitness, weight training, and biking.
  
  
  METHODS
  Twenty men with exercise addiction as defined by the Exercise Addiction Inventory (EAI scores 24-30) and 20 men in an exercise control group (EAI scores 6-16) matched on body mass index.
  
  
  METHODS
  Plasma leptin and sex hormones were measured in blood samples collected under fasting and resting conditions. Body composition was assessed by dual-energy x-ray absorptiometry. Eating disorder symptoms were identified by the Eating Disorder Inventory 2.
  
  
  RESULTS
  The exercise addiction group had significantly (P < 0.001) lower leptin levels (1.1 μg/L, SD = 1.3) than controls (4.3 μg/L, SD = 2.9). Even when adjusted for body fat percentage, the addiction group had significantly (P < 0.001) lower leptin levels (0.1 μg/L, SD = 0.1) than the controls (0.2 μg/L, SD = 0.1). Body fat-adjusted leptin correlated with free bioavailable testosterone, but it was only significant in nonaddictive exercisers. None of the exercisers seemed to suffer from an eating disorder.
  
  
  CONCLUSIONS
  This is the first study showing that excessive training in exercise addiction is associated with low levels of body fat-adjusted leptin levels.
  
  
  CONCLUSIONS
  Hypoleptinemia could be involved in the pathogenesis of exercise addiction. However, further studies are needed to explore the potential causal relationship.
authors.affiliation: *Centre for Eating Disorders, Institute of Clinical Research, Odense University Hospital, University of Southern Denmark, Odense, Denmark; †Department of Endocrinology, Institute of Clinical Research, Odense University Hospital, University of Southern Denmark, Odense, Denmark; ‡Medical Research Laboratory, Department of Clinical Medicine, Aarhus University, Aarhus C, Denmark; and §Department of Endocrinology, Centre for Eating Disorders, Odense University Hospital, Odense, Denmark.
authors.forename: Mia B
authors.initials: MB
authors.lastname: Lichtenstein
authors.forename: Alin
authors.initials: A
authors.lastname: Andries
authors.forename: Stinus
authors.initials: S
authors.lastname: Hansen
authors.forename: Jan
authors.initials: J
authors.lastname: Frystyk
authors.forename: René K
authors.initials: RK
authors.lastname: Støving
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D016739:Behavior, Addictive / Q000378:metabolism* / Q000523:psychology; D001823:Body Composition; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D015444:Exercise / Q000523:psychology*; D006801:Humans; D020738:Leptin / Q000378:metabolism*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D013739:Testosterone / Q000378:metabolism; D055815:Young Adult
chemical_list: D020738:Leptin; D013739:Testosterone