title: Basal metabolic rate and thyroid hormones of late-middle-aged and older human subjects: the ZENITH study.
abstract: OBJECTIVE
  This paper describes baseline data on basal metabolic rate (BMR), thyroid hormone levels and body composition of middle-aged and older people participating in the ZENITH project and the correlation of thyroid hormone levels with zinc status.
  
  
  METHODS
  A multicentre prospective intervention study employing a randomised double blind design.
  
  
  METHODS
  Clermont-Ferrand, Theix (France), Coleraine (Northern Ireland), Grenoble (France), Rome (Italy).
  
  
  METHODS
  BMR has been measured on a subsample of 70 middle-aged volunteers (35 men and 35 women recruited in Clermont-Ferrand, France, aged 55-70 y) and 108 older volunteers (56 men and 52 women recruited in Rome, Italy, aged 70-85 y). Thyroid hormone levels were evaluated in the entire group of ZENITH volunteers (n = 387). BMR was measured by indirect calorimetry. Fat-free mass (FFM) was derived by four skinfold thicknesses using Durnin and Womersley's equations. Concentrations of thyroid hormones (total T3 and T4) were measured using a competitive immunoassay with an enhanced chemiluminescence end point.
  
  
  RESULTS
  Italian older volunteers had a significantly lower FFM than middle-aged French volunteers (-7% P < 0.01). A negative correlation between BMR and age (men, r = -0.64; women, r = -0.62; both P < 0.0001) was observed: BMR was significantly (P < 0.000001) lower in Italian elderly volunteers (4.03+/-0.46 kJ/min and 3.29+/-0.42 kJ/min for men and women, respectively) than in middle-aged French volunteers (4.84+/-0.45 kJ/min and 3.87+/-0.38 kJ/min for men and women, respectively), even after adjustment for FFM (-12%). No correlation has been observed between BMR and thyroid hormones both in French and Italian subjects. Total T4 (TT4) concentrations were lowest in middle-aged population (-10%, P < 0.0001). A moderate negative correlation has been found with TT4 and red blood cell zinc (r = -0.12, P < 0.02, slope -0.026).
  
  
  CONCLUSIONS
  The results confirm an age-related decline in BMR not entirely explained by body composition or thyroid hormones differences.
authors.affiliation: Centre de Recherche en Nutrition Humaine d'Auvergne, Unité des Maladies Mé taboliques et Micronutrients, INRA, Clermont-Ferrand/Theix, France.
authors.forename: N
authors.initials: N
authors.lastname: Meunier
authors.forename: J H
authors.initials: JH
authors.lastname: Beattie
authors.forename: D
authors.initials: D
authors.lastname: Ciarapica
authors.forename: J M
authors.initials: JM
authors.lastname: O'Connor
authors.forename: M
authors.initials: M
authors.lastname: Andriollo-Sanchez
authors.forename: A
authors.initials: A
authors.lastname: Taras
authors.forename: C
authors.initials: C
authors.lastname: Coudray
authors.forename: A
authors.initials: A
authors.lastname: Polito
mesh_terms: D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D001481:Basal Metabolism / Q000502:physiology*; D001823:Body Composition / Q000502:physiology; D002153:Calorimetry, Indirect / Q000379:methods; D004311:Double-Blind Method; D005060:Europe; D005260:Female; D006801:Humans; D008163:Luminescent Measurements / Q000379:methods; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D011446:Prospective Studies; D012737:Sex Factors; D012885:Skinfold Thickness; D013963:Thyroid Hormones / Q000097:blood*; D015032:Zinc / Q000097:blood
chemical_list: D013963:Thyroid Hormones; D015032:Zinc