title: The effects of a higher protein intake during energy restriction on changes in body composition and physical function in older women.
abstract: BACKGROUND
  The purpose of this double-blind randomized clinical trial was to compare the relative effectiveness of a higher protein and conventional carbohydrate intake during weight loss on body composition and physical function in older women.
  
  
  METHODS
  Thirty-one overweight or obese, postmenopausal women (mean ± SD: age 65.2 ± 4.6 years, body mass index 33.7 ± 4.9 kg/m(2)) were prescribed a reduced calorie diet (1,400 kcal/day; 15%, 65%, 30% energy from protein, carbohydrate, and fat, respectively) and randomly assigned to 2 × 25 g/day whey protein (PRO n = 15) or maltodextrin (CARB n = 16) supplementation for 6 months. Lean soft tissue (LST) via dual-energy X-ray absorptiometry; thigh muscle, subcutaneous adipose tissue (SAT), and intermuscular adipose tissue with magnetic resonance imaging; knee strength with isokinetic dynamometry; balance and physical function with a battery of performance tests.
  
  
  RESULTS
  PRO lost more weight than CARB (-8.0% ± 6.2%, -4.1% ± 3.6%, p = .059; respectively). Changes in LST, %LST, and strength, balance, or physical performance measures did not differ between groups (all p > .05). Weight to leg LST ratio improved more in PRO versus CARB (-4.6 ± 3.6%, -1.8 ± 2.6%, p = .03). PRO lost 4.2% more muscle (p = .01), 10.9% more SAT (p = .02), and 8.2% more intermuscular adipose tissue (p = .03) than CARB. Relative to thigh volume changes, PRO gained 5.8% more muscle (p = .049) and lost 3.8% greater SAT (p = .06) than CARB. Weight to leg LST ratio (r(2) = .189, p = .02) and SAT (r(2) = .163, p = .04) predicted improved up and go, relative muscle (r(2) = .238, p = .01) and SAT (r(2) = .165, p = .04) predicted improved transfer test, and %LST predicted improved balance (r(2) = .179, p = .04).
  
  
  CONCLUSIONS
  A higher protein intake during caloric restriction maintains muscle relative to weight lost, which in turn enhances physical function in older women.
authors.affiliation: Department of Sports Medicine, Institute of Sports Sciences, Justus Liebig University Giessen, Kugelberg 62, 35394 Giessen, Germany. mina.mojtahedi@gmail.com
authors.forename: Mina C
authors.initials: MC
authors.lastname: Mojtahedi
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Thorpe
authors.forename: Dimitrios C
authors.initials: DC
authors.lastname: Karampinos
authors.forename: Curtis L
authors.initials: CL
authors.lastname: Johnson
authors.forename: Donald K
authors.initials: DK
authors.lastname: Layman
authors.forename: John G
authors.initials: JG
authors.lastname: Georgiadis
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Evans
mesh_terms: D000368:Aged; D001823:Body Composition / Q000502:physiology*; D031204:Caloric Restriction; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000502:physiology; D015431:Weight Loss / Q000502:physiology*
chemical_list: D004040:Dietary Carbohydrates; D004044:Dietary Proteins