Original articleMediterranean diet, Dietary Approaches to Stop Hypertension (DASH) style diet, and metabolic health in U.S. adults
Introduction
Obesity is associated with an increased risk of type 2 diabetes and cardiovascular disease (CVD) [1], but not all obese individuals are equally susceptible to cardiometabolic risk. Within the same category of body mass index (BMI), a subgroup of obese individuals who have normal metabolic characteristics has been identified as metabolically healthy obese (MHO) phenotype, compared with metabolically unhealthy obese (MUO) phenotype [2], [3], [4]. In addition, a subgroup of normal weight individuals who are susceptible to metabolic abnormalities has been referred to as metabolically obese normal weight (MONW) phenotype [5], [6], [7].
It is well known that the Mediterranean diet and the Dietary Approaches to Stop Hypertension (DASH) style diets are associated with lower risk of cardiometabolic disease [8]. Both dietary patterns are hypothesis-driven diets characterized by key components: the Mediterranean diet relies on the dietary habits adopted by population living in the Mediterranean area and is characterized by high content of fruit, vegetables, legumes, fish, nuts, and unsaturated fatty acids from vegetable sources including a large amount from olive oil [9], [10]; the DASH diet takes into account macro- and micro-nutrients demonstrated to be effective in reducing risk of hypertension [11]. Underlying mechanisms for cardiovascular health benefits of Mediterranean diet and DASH style diet are complex, but can be explained by the improvement of cardiometabolic profiles including insulin resistance, lipid profiles, blood pressure, and inflammatory markers [12]. Therefore, it is plausible that adherence to Mediterranean diet and DASH style diets might be positively associated with a metabolically healthy phenotype.
Several studies have explored associations between dietary factors and metabolic phenotypes. However, these reports have been limited to MHO phenotype [13], especially without considering dietary pattern [14], or with specific age groups [15]. A few studies have reported associations in MONW phenotype in non-US population [16], but with limited generalizability [17]. Several studies demonstrated that dietary factors are related to metabolic phenotype in both obese and normal weight population [18], but only focused on women [19], or single foods such as olive oil [20]. However, limited data exist on the relationship of Mediterranean diet and DASH diet with metabolic phenotypes, especially for a potential differential association by age groups with substantially different cardiovascular risk.
It has been suggested that the risk of developing coronary heart disease significantly increases after 45 years in men [21] and in postmenopausal women [22]. In addition, it is reported that the association between Mediterranean diet and atherothrombotic biomarkers is largely different between men <45 years and men ≥45 years as well as premenopausal and postmenopausal women [23]. Another study showed that the Healthy Eating Index score was associated with MHO phenotype only in younger age group [13].
Therefore, we aimed to identify the association of Mediterranean diet and DASH style diet with MHO and MONW phenotypes in a nationally representative U.S. population, with a priori hypothesis that this association should be different according to the two age groups exhibiting a substantial difference in cardiovascular risk; less than or greater than 45 years in men; before or after menopause in women.
Section snippets
Study population
We used data from the Third National Health and Nutrition Examination Survey (NHANES III), 1988–1994 for this analysis. A complex multi-stage stratified clustered probability sample design was used to achieve a nationally representative sample of the civilian, non-institutionalized US population. The survey included personal interviews, physical examinations, and laboratory measurements.
We included 3858 normal weight (18.5 ≤ BMI < 25 kg/m2) and obese (BMI ≥ 30 kg/m2) adults aged 20–90 years
Statistical analysis
Descriptive statistics were computed for the sample across the presence or absence of MHO phenotype and MONW phenotype in each age group. Continuous variables were presented by mean (SE: standard error) and compared using linear regression analyses. Response variables that were non-normally distributed were log-transformed to meet normality assumptions. Categorical variables were expressed by percentage with SE and were compared using Rao-Scott χ2 tests. We used the appropriate survey
Results
MHO and MONW phenotypes were observed in 40.5% and 10.2% in the younger age group; 19.0% and 40.5% in the older age group, respectively. General and clinical characteristics according to the presence or absence of MHO and MONW phenotypes in both age groups are shown in Table 1 and Supplemental Table S2. MHO individuals were less likely to be non-Hispanic white; had more favorable metabolic parameters in both age groups, and were less likely to have CHD family history and DM parental history in
Discussion
In this nationally representative sample of U.S. adults, the Mediterranean diet and DASH style diet were favorably associated with metabolic phenotypes in the younger age group that included men <45 years and premenopausal women. More specifically, MDS was positively associated with MHO phenotype, whereas the DASH index was inversely associated with the MONW phenotype, independent of a wide range of potential confounders. MDS and DASH index were not associated with MHO and MONW phenotypes in
Conflict of interest
None of the authors reported a conflict of interest related to the study.
Statement of authorship
YMP, ATM, SES, TTF, JZ, and LJH: project conception, development of overall research plan; YMP, KH, and JZ: statistical analyses; YMP: writing of the manuscript; YMP, ATM, SES, TTF, JZ, LJH, LSH, HSK: interpretation of the data and critical revision of the manuscript for important intellectual content. YMP and ATM: had primary responsibility for final content. All authors read and approved the final manuscript.
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