A 14-item Mediterranean diet assessment tool and obesity indexes among high-risk subjects: the PREDIMED trial

Abstract

Objective: Independently of total caloric intake, a better quality of the diet (for example, conformity to the Mediterranean diet) is associated with lower obesity risk. It is unclear whether a brief dietary assessment tool, instead of full-length comprehensive methods, can also capture this association. In addition to reduced costs, a brief tool has the interesting advantage of allowing immediate feedback to participants in interventional studies. Another relevant question is which individual items of such a brief tool are responsible for this association. We examined these associations using a 14-item tool of adherence to the Mediterranean diet as exposure and body mass index, waist circumference and waist-to-height ratio (WHtR) as outcomes.

Design: Cross-sectional assessment of all participants in the "PREvención con DIeta MEDiterránea" (PREDIMED) trial.

Subjects: 7,447 participants (55-80 years, 57% women) free of cardiovascular disease, but with either type 2 diabetes or ≥ 3 cardiovascular risk factors. Trained dietitians used both a validated 14-item questionnaire and a full-length validated 137-item food frequency questionnaire to assess dietary habits. Trained nurses measured weight, height and waist circumference.

Results: Strong inverse linear associations between the 14-item tool and all adiposity indexes were found. For a two-point increment in the 14-item score, the multivariable-adjusted differences in WHtR were -0.0066 (95% confidence interval, -0.0088 to -0.0049) for women and -0.0059 (-0.0079 to -0.0038) for men. The multivariable-adjusted odds ratio for a WHtR>0.6 in participants scoring ≥ 10 points versus ≤ 7 points was 0.68 (0.57 to 0.80) for women and 0.66 (0.54 to 0.80) for men. High consumption of nuts and low consumption of sweetened/carbonated beverages presented the strongest inverse associations with abdominal obesity.

Conclusions: A brief 14-item tool was able to capture a strong monotonic inverse association between adherence to a good quality dietary pattern (Mediterranean diet) and obesity indexes in a population of adults at high cardiovascular risk.

Figure 1. Multivariable-adjusted odds ratios (OR, 95% confidence intervals) for abdominal obesity (waist-to-height>0.6) by adherence to the Mediterranean diet.

Adjusted for sex, age, smoking and centre.

Figure 2. Adjusted differences in BMI for 7 selected items in the 14-point score of adherence to the Mediterranean diet independently associated with BMI.

Olive oil: Use of olive oil as the main culinary lipid (first item of the score). Adjusted for sex, age, smoking, centre and for all the 14 items. For 1) red/processed meats, 2) sugared soda drinks, 3) commercial bakery, sweets and cakes the inverse of the item was used (i.e. a higher consumption was associated with a higher BMI).

Figure 3. Adjusted differences in % waist-to-height ratio (95% confidence intervals)¹ for selected items in the 14-point score of adherence to the Mediterranean diet independently associated with the waist-to-height ratio.

Olive oil: Use of olive oil as the main culinary lipid (first item of the score). ¹A waist-to-height ratio = 1 is taken as 100%. Adjusted for sex, age, smoking, centre and for all the 14 items. For 1) red/processed meats, 2) sugared soda drinks, 3) commercial bakery, sweets and cakes, the inverse of the item was used (i.e. a higher consumption was associated with a higher waist to height ratio).