Dieting attempts modify the association between quality of diet and obesity

Evidence on the nature of the relationship between obesity and the quality of diet remains controversial. Likewise, the possible effect of dieting attempts on this association is poorly understood. This study investigates the possible modifying effect of dieting attempts on the association between the quality of diet and obesity. The authors hypothesize that among dieters the association may be biased. The study was based on a Finnish cohort, including 5910 men and women aged 30 to 99 years, with information on diet and body mass index (BMI). Using data from a food frequency questionnaire (FFQ), an Alternate Healthy Eating Index (AHEI) applicable to the Finnish regimen was formed. Obesity was defined as a BMI ≥30 kg/m2. Information on dieting attempts was collected using a questionnaire. The statistical analyses were based on linear and logistic regression. We found a positive association between the quality of the diet and obesity, the relative odds of obesity between the highest and lowest quintiles of AHEI being 1.48 (95% CI, 1.20-1.82) after adjustment for confounding factors. However, in the interaction analysis of dieting attempts and AHEI, no association was observed in non-dieters (OR, 0.92; 95% CI, 0.69-1.24) but among dieters a slightly elevated risk was found (OR, 1.40; 95% CI, 0.98-1.98). We found no association between a high quality diet and obesity among non-dieters, but a tendency for a positive association in dieters. Dieting thus seems to modify the association between diet and obesity, which should be further studied using a longitudinal design.