Assessing dietary fat intake in chronic disease rehabilitation programs

Previous work has established that the Heart Fit Rx Diet Habits Survey (HFD), formerly the Food Frequency Assessment Tool, compares favorably (r = 0.78; P <.01) with the Oregon Health Sciences University Diet Habit Survey. The purpose of this study was to assess the validity and reliability of the HFD in estimating fat intake as a percentage of calories.

The validity study assessed 137 patients undergoing cardiac rehabilitation (age, 60.7 +/- 11.3 years) who completed the HFD (29 questions, 11 of which were dietary fat related [fat subscore]) and a 3-day food record. A regression equation was obtained using HFD subscores to estimate fat intake as a percentage of calories. The regression equation was tested using 50 patients not included in the original cohort. Reliability was assessed using a third group of 31 patients in a 4-week test-retest analysis.

The correlation coefficient between the 3-day record and the HFD fat subscore was 0.65 (P <.01). The correlation coefficient for women (r = 0.77) was slightly higher than for men (r = 0.62). The regression equation derived from the HFD fat subscore was as follows: percentage of dietary fat = 50.65 - 0.736 (HFD fat subscore). The correlation coefficient for actual and predicted values was 0.58 (P <.01). Differences between estimated fat intake, as determined by the 3-day record and the HFD, ranged from 0% to 25% and were within 5% for 26 of the 50 subjects (52%), and within 10% for 41 of the 50 subjects (82%). The mean difference between the two measures was 1.5% (P =.17). Test-retest reliability was high for both the HFD total score (r = 0.95) and the HFD fat subscore (r = 0.85; P <.01).

The HFD is an inexpensive, valid, and reliable clinical instrument for assessing dietary fat. It can be a viable alternative to other time-consuming methods, including computerized analysis.