title: Weight loss in humans in space.
abstract: BACKGROUND
  Bodyweight loss during spaceflight has been observed among astronauts since the early space missions. Considerable mission data has been accumulated, including data from female astronauts, on the many Shuttle and International Space Station missions. The purpose of this study was to investigate the association between observed weight loss during spaceflight and potential covariate factors.
  
  
  METHODS
  We performed a statistical analysis of the association between bodyweight change and plausible clinical and mission covariates, using data obtained from the NASA Longitudinal Study of Astronaut Health (LSAH).
  
  
  RESULTS
  We confirmed that spaceflight is associated with weight change (-2.1 +/- 0.1%, N = 514). Prospective predictors of weight loss included: being a first-time astronaut, preflight bodyweight and BMI, routinely performing preflight exercise sessions lasting greater than 1 h, and baseline levels of cholesterol, potassium, and chloride. Severe space motion sickness was significantly associated with greater weight loss. Unexpectedly, a higher number of extravehicular activities per mission protected against weight loss. Mission duration had the strongest association with bodyweight change (-2.4 +/- 0.4% per 100 d in space).
  
  
  CONCLUSIONS
  On average, space missions are associated with cumulative loss of bodyweight over time. Unless effective countermeasures are implemented, significant weight loss will be a likely outcome in a subset of astronauts as mission durations increase. New predictors of intra-mission bodyweight changes and other associated factors are identified.
authors.affiliation: Japan Aerospace Exploration Agency, Tsukuba, Japan. matsumoto.akiko@jaxa.jp
authors.forename: Akiko
authors.initials: A
authors.lastname: Matsumoto
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Storch
authors.forename: Adrienne
authors.initials: A
authors.lastname: Stolfi
authors.forename: Stanley R
authors.initials: SR
authors.lastname: Mohler
authors.forename: Mary Anne
authors.initials: MA
authors.lastname: Frey
authors.forename: T Peter
authors.initials: TP
authors.lastname: Stein
mesh_terms: D000704:Analysis of Variance; D000886:Anthropometry; D015415:Biomarkers / Q000032:analysis; D016009:Chi-Square Distribution; D003710:Demography; D005260:Female; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D012307:Risk Factors; D013026:Space Flight; D013997:Time Factors; D015431:Weight Loss
chemical_list: D015415:Biomarkers