A healthy quality Mediterranean-like diet partially modifies the association between obesity and cardiovascular disease (CVD) mortality, according to a study from Uppsala University, Sweden.
Higher body mass (BMI) accounted for 4.0m deaths globally in 2015 and more than two-thirds of those deaths were due to cardiovascular disease (CVD). Studies have suggested that other factors, including healthy dietary patterns, might modify the higher risk of CVD associated with higher BMI. In this study, researchers studied BMI, diet and mortality among 79,003 Swedish adults enrolled in the Swedish Mammography Cohort and Cohort of Swedish Men. Adherence to a Mediterranean-like diet (mMED) was assessed on a scale of 0 to 8, integrating information on intake of fruits and vegetables, legumes, nuts, unrefined or high-fibre grains, fish, red and processed meat, and olive oil. Information was also available on age, physical activity, smoking and socioeconomics of the cohort participants.
Over 21 years of follow-up, 30,389 (38% of participants) died. Among overweight individuals, the group with the lowest hazard ratio (HR) of all-cause mortality were those with high mMED (HR 0.94; 95% CI 0.90-0.98 compared with those with normal weight and high mMED). Obese individuals who also had high mMED did not have a significantly higher mortality compared with those with normal weight and high mMED (HR 1.03; 95%CI 0.96-1.11). Conversely, individuals with a normal BMI but low mMED had a higher mortality (HR 1.60; 95%CI 1.48-1.74) than those with normal weight and high mMED. For CVD mortality, which represented 12,064 of the deaths, the findings were broadly similar. However, while CVD morality associated with high BMI was reduced by adherence to a Mediterranean diet, it was not fully countered. Moreover, lower BMI did not counter the elevated CVD mortality associated with a low mMED.
“These results indicate that adherence to healthy diets such as a Mediterranean-like diet may be a more appropriate focus that avoidance of obesity for the prevention of overall mortality,” the authors say. “Nonetheless, a healthy diet may not completely counter higher CVD mortality related with obesity.”
Abstract
Background: It is unclear whether the effect on mortality of a higher body mass index (BMI) can be compensated for by adherence to a healthy diet and whether the effect on mortality by a low adherence to a healthy diet can be compensated for by a normal weight. We aimed to evaluate the associations of BMI combined with adherence to a Mediterranean-like diet on all-cause and cardiovascular disease (CVD) mortality.
Methods and findings: Our longitudinal cohort design included the Swedish Mammography Cohort (SMC) and the Cohort of Swedish Men (COSM) (1997–2017), with a total of 79,003 women (44%) and men (56%) and a mean baseline age of 61 years. BMI was categorized into normal weight (20–24.9 kg/m2), overweight (25–29.9 kg/m2), and obesity (30+ kg/m2). Adherence to a Mediterranean-like diet was assessed by means of the modified Mediterranean-like diet (mMED) score, ranging from 0 to 8; mMED was classified into 3 categories (0 to <4, 4 to <6, and 6–8 score points), forming a total of 9 BMI × mMED combinations. We identified mortality by use of national Swedish registers. Cox proportional hazard models with time-updated information on exposure and covariates were used to calculate the adjusted hazard ratios (HRs) of mortality with their 95% confidence intervals (CIs). Our HRs were adjusted for age, baseline educational level, marital status, leisure time physical exercise, walking/cycling, height, energy intake, smoking habits, baseline Charlson’s weighted comorbidity index, and baseline diabetes mellitus. During up to 21 years of follow-up, 30,389 (38%) participants died, corresponding to 22 deaths per 1,000 person-years. We found the lowest HR of all-cause mortality among overweight individuals with high mMED (HR 0.94; 95% CI 0.90, 0.98) compared with those with normal weight and high mMED. Using the same reference, obese individuals with high mMED did not experience significantly higher all-cause mortality (HR 1.03; 95% CI 0.96–1.11). In contrast, compared with those with normal weight and high mMED, individuals with a low mMED had a high mortality despite a normal BMI (HR 1.60; 95% CI 1.48–1.74). We found similar estimates among women and men. For CVD mortality (12,064 deaths) the findings were broadly similar, though obese individuals with high mMED retained a modestly increased risk of CVD death (HR 1.29; 95% CI 1.16–1.44) compared with those with normal weight and high mMED. A main limitation of the present study is the observational design with self-reported lifestyle information with risk of residual or unmeasured confounding (e.g., genetic liability), and no causal inferences can be made based on this study alone.
Conclusions: These findings suggest that diet quality modifies the association between BMI and all-cause mortality in women and men. A healthy diet may, however, not completely counter higher CVD mortality related to obesity.
Authors
Karl Michaëlsson, John A Baron, Liisa Byberg, Jonas Höijer, Susanna C Larsson, Bodil Svennblad, Håkan Melhus, Alicja Wolk, Eva Warensjö Lemming
[link url="https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003331"]PLOS Medicine abstract[/link]