title: Monitoring dietary change in a low-fat diet intervention study: advantages of using 24-hour dietary recalls vs food records.
abstract: OBJECTIVE
  The purpose of the study was to evaluate two methods of dietary assessment for monitoring change in fat intake in a low-fat diet intervention study.
  
  
  METHODS
  The two dietary assessment methods were a 4-day food record (4DFR) and an unannounced 24-hour dietary recall conducted by telephone interview (referred to as a telephone recall [TR]). Subjects were assigned randomly to either a low-fat diet intervention group or a control group that received no counseling about fat intake. Dietary data were collected at baseline, 6 months, and 12 months.
  
  
  METHODS
  Two hundred ninety postmenopausal women with localized breast cancer were recruited at seven clinical centers in the United States.
  
  
  METHODS
  Analysis of variance was used to test for significant differences in mean fat and energy intakes.
  
  
  RESULTS
  Three sources of error were identified: (a) an instrument effect, suggesting underreporting at baseline of approximately 8% in mean energy intake and 11% in mean fat intake in the TR group compared with the 4DFR group (P = .0001); (b) a repeated measures effect observed for the 4DFR, suggesting underreporting of approximately 7% for energy intake and 14% for fat intake in the control group at 6 and 12 months compared with baseline values (P < .001); and (c) an adherence effect (or compliance bias), suggesting greater compliance to the low-fat intervention diet when subjects were keeping food records than when estimates were based on the unannounced TR. Compared with the TR, the 4DFR overestimated the extent of fat reduction in the low-fat diet intervention group by 41% (P = .08) and 25% (P = .62) at 6 and 12 months, respectively.
  
  
  CONCLUSIONS
  Multiple days of unannounced 24-hour recalls may be preferable to multiple-day food records for monitoring dietary change in diet intervention studies.
authors.affiliation: Department of Preventive Medicine and Community Health, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298, USA.
authors.forename: I M
authors.initials: IM
authors.lastname: Buzzard
authors.forename: C L
authors.initials: CL
authors.lastname: Faucett
authors.forename: R W
authors.initials: RW
authors.lastname: Jeffery
authors.forename: L
authors.initials: L
authors.lastname: McBane
authors.forename: P
authors.initials: P
authors.lastname: McGovern
authors.forename: J S
authors.initials: JS
authors.lastname: Baxter
authors.forename: A C
authors.initials: AC
authors.lastname: Shapiro
authors.forename: G L
authors.initials: GL
authors.lastname: Blackburn
authors.forename: R T
authors.initials: RT
authors.lastname: Chlebowski
authors.forename: R M
authors.initials: RM
authors.lastname: Elashoff
authors.forename: E L
authors.initials: EL
authors.lastname: Wynder
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D015930:Diet Records; D018752:Diet, Fat-Restricted / Q000592:standards*; D005260:Female; D006801:Humans; D011939:Mental Recall; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000379:methods*; D015596:Nutrition Assessment; D010349:Patient Compliance; D013689:Telephone; D013997:Time Factors