title: Effect of Chronic Athletic Activity on Brown Fat in Young Women.
abstract: BACKGROUND
  The effect of chronic exercise activity on brown adipose tissue (BAT) is not clear, with some studies showing positive and others showing negative associations. Chronic exercise is associated with increased resting energy expenditure (REE) secondary to increased lean mass and a probable increase in BAT. Many athletes are in a state of relative energy deficit suggested by lower fat mass and hypothalamic amenorrhea. States of severe energy deficit such as anorexia nervosa are associated with reduced BAT. There are no data regarding the impact of chronic exercise activity on BAT volume or activity in young women and it is unclear whether relative energy deficiency modifies the effects of exercise on BAT.
  
  
  OBJECTIVE
  We assessed cold induced BAT volume and activity in young female athletes compared with non-athletes, and further evaluated associations of BAT with measures of REE, body composition and menstrual status.
  
  
  METHODS
  The protocol was approved by our Institutional Review Board. Written informed consent was obtained from all participants prior to study initiation. This was a cross-sectional study of 24 women (16 athletes and8 non-athletes) between 18-25 years of age. Athletes were either oligo-amenorrheic (n = 8) or eumenorrheic (n = 8).We used PET/CT scans to determine cold induced BAT activity, VMAX Encore 29 metabolic cart to obtain measures of REE, and DXA for body composition.
  
  
  RESULTS
  Athletes and non-athletes did not differ for age or BMI. Compared with non-athletes, athletes had lower percent body fat (p = 0.002), higher percent lean mass (p = 0.01) and trended higher in REE (p = 0.09). BAT volume and activity in athletes trended lower than in non-athletes (p = 0.06; p = 0.07, respectively). We found negative associations of BAT activity with duration of amenorrhea (r = -0.46, p = 0.02).BAT volume correlated inversely with lean mass (r = -0.46, p = 0.02), and positively with percent body fat, irisin and thyroid hormones.
  
  
  CONCLUSIONS
  Our study shows a trend for lower BAT in young female athletes compared with non-athletes, and shows associations of brown fat with menstrual status and body composition. Brown fat may undergo adaptive reductions with increasing energy deficit.
authors.affiliation: Pediatric Endocrine Unit, Massachusetts General Hospital and Harvard Medical School Boston, Massachusetts, United States of America.|Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Vibha
authors.initials: V
authors.lastname: Singhal
authors.affiliation: Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Giovana D
authors.initials: GD
authors.lastname: Maffazioli
authors.affiliation: Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.|Division of Sports Medicine, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Kate E
authors.initials: KE
authors.lastname: Ackerman
authors.affiliation: Department of Biostatistics, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Hang
authors.initials: H
authors.lastname: Lee
authors.affiliation: Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Elisa F
authors.initials: EF
authors.lastname: Elia
authors.affiliation: Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Ryan
authors.initials: R
authors.lastname: Woolley
authors.affiliation: Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Gerald
authors.initials: G
authors.lastname: Kolodny
authors.affiliation: Diabetes, Endocrinology, and Obesity Branch, NIDDK, NIH, Bethesda, Maryland, United States of America.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Cypess
authors.affiliation: Pediatric Endocrine Unit, Massachusetts General Hospital and Harvard Medical School Boston, Massachusetts, United States of America.|Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Madhusmita
authors.initials: M
authors.lastname: Misra
mesh_terms: D015502:Absorptiometry, Photon; D002001:Adipose Tissue, Brown / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000568:Amenorrhea / Q000209:etiology; D056352:Athletes; D001481:Basal Metabolism; D001823:Body Composition; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D000072078:Positron Emission Tomography Computed Tomography; D013177:Sports / Q000502:physiology*; D055815:Young Adult