title: Examination of cognitive function during six months of calorie restriction: results of a randomized controlled trial.
abstract: BACKGROUND
  Calorie restriction increases longevity in many organisms, and calorie restriction or its mimetic might increase longevity in humans. It is unclear if calorie restriction/dieting contributes to cognitive impairment. During this randomized controlled trial, the effect of 6 months of calorie restriction on cognitive functioning was tested.
  
  
  METHODS
  Participants (n = 48) were randomized to one of four groups: (1) control (weight maintenance), (2) calorie restriction (CR; 25% restriction), (3) CR plus structured exercise (CR + EX, 12.5% restriction plus 12.5% increased energy expenditure via exercise), or (4) low-calorie diet (LCD; 890 kcal/d diet until 15% weight loss, followed by weight maintenance). Cognitive tests (verbal memory, visual memory, attention/concentration) were conducted at baseline and months 3 and 6. Mixed linear models tested if cognitive function changed significantly from baseline to months 3 and 6, and if this change differed by group. Correlation analysis was used to determine if average daily energy deficit (quantified from change in body energy stores) was associated with change in cognitive test performance for the three dieting groups combined.
  
  
  RESULTS
  No consistent pattern of verbal memory, visual retention/memory, or attention/concentration deficits emerged during the trial. Daily energy deficit was not significantly associated with change in cognitive test performance.
  
  
  CONCLUSIONS
  This randomized controlled trial suggests that calorie restriction/dieting was not associated with a consistent pattern of cognitive impairment. These conclusions must be interpreted in the context of study limitations, namely small sample size and limited statistical power. Previous reports of cognitive impairment might reflect sampling biases or information processing biases.
authors.affiliation: Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA. martinck@pbrc.edu
authors.forename: Corby K
authors.initials: CK
authors.lastname: Martin
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Anton
authors.forename: Hongmei
authors.initials: H
authors.lastname: Han
authors.forename: Emily
authors.initials: E
authors.lastname: York-Crowe
authors.forename: Leanne M
authors.initials: LM
authors.lastname: Redman
authors.forename: Eric
authors.initials: E
authors.lastname: Ravussin
authors.forename: Donald A
authors.initials: DA
authors.lastname: Williamson
mesh_terms: D000328:Adult; D001288:Attention; D031204:Caloric Restriction; D003071:Cognition; D004038:Diet, Reducing; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D006801:Humans; D008136:Longevity; D008297:Male; D008568:Memory; D008875:Middle Aged; D050177:Overweight / Q000502:physiology*; D014706:Verbal Learning