Low-Fat Diet and Weight Change in Postmenopausal WomenLow-Fat Diet and Weight Change in Postmenopausal Women

To the Editor: In their study of low-fat diet and weight change, Dr Howard and colleagues¹ reported mean 1-year and 7.5-year follow-up results comparing a group of women randomized to promote a low-fat diet with a control group randomized to a self-selected diet. They concluded that a low-fat eating pattern does not result in weight gain in postmenopausal women.

The mean weights of the women in the 2 groups did not differ at baseline (76.8 kg, low-fat group; 76.7 kg, control group). On average, the low-fat group weighed less than the control group at 1 year (1.9 kg less) and at 7.5 years (0.4 kg less). Although statistically significant, the actual magnitudes of these differences were small, especially given the study time frame of several years.

However, Table 2 shows that the mean daily caloric intake of the low-fat group was approximately 120 kcal less than the control group. If accurate, the total differential caloric intake over an average of 7.5 years would exceed 300 000 kcal. The authors report that no recommendation was made concerning exercising and that neither baseline nor end point measures of physical activity were significantly different between the 2 groups.

Using a commonly accepted conversion factor of approximately 7700 kcal per kg,² this energy imbalance should lead to as much as 5.6 kg and 42 kg weight differentials between the 2 groups at 1 year and 7.5 years, respectively. The authors do not address this apparent paradox in the substantial caloric differential between the 2 study groups with virtually no corresponding weight change differential.