Better Diet Quality Linked to Lower Heart Risk in Overweight Adults, Study Finds

A new study of 672 overweight and obese adults in Iran suggests that the quality of what people eat, measured by a structured scoring system known as the Lifelines Diet Score, is closely linked to a suite of biochemical and anthropometric markers that cardiologists use to gauge hidden cardiovascular danger. The research, published in BMC Endocrine Disorders, found that people whose diets scored highest carried significantly lower levels of atherogenic risk than those whose diets scored lowest, even after accounting for age, sex, education, smoking, physical activity, and total energy intake. The finding matters because it extends the evidence base for a diet quality metric originally developed in a Dutch population into a Middle Eastern clinical setting, where dietary patterns, food availability, and obesity-related metabolic profiles differ substantially from those of Western Europe.

The study was conducted as a cross-sectional investigation, meaning that researchers measured diet and cardiometabolic markers at a single point in time rather than following participants over years. Participants were recruited from outpatient endocrine clinics in Zanjan, a city in northwestern Iran, and the work was approved by the Ethics Committee of Zanjan University of Medical Sciences under the Declaration of Helsinki, with all participants providing written informed consent before enrollment. The single-author study, led by Mohammed Yousif Merza of Hawler Medical University in Erbil, received no external funding, and the author declared no competing interests.

To capture habitual eating behavior, the researchers used a validated 168-item food frequency questionnaire asking participants to recall their intake over the previous year. From those responses, the team calculated the Lifelines Diet Score, or LLDS, a metric built from 12 food groups. Unlike some diet indices that simply reward or penalize foods based on arbitrary thresholds, the LLDS scores food groups according to their relative intake within the study population, weighting both healthful groups such as vegetables, fruit, whole grains, legumes, nuts, dairy, fish, and unsweetened coffee and tea, and unhealthful groups such as red and processed meat, butter and margarine, sugar-sweetened beverages, and alcohol. Participants were then sorted into tertiles, or thirds, of diet quality, allowing the investigators to compare those with the highest scores against those with the lowest.

The primary outcome was the Atherogenic Index of Plasma, abbreviated AIP, a composite measure derived from blood lipids that reflects the balance between pro-atherogenic and anti-atherogenic fractions of circulating fat. AIP is typically calculated from triglycerides and high-density lipoprotein cholesterol, and higher values are associated with a greater burden of small, dense LDL particles, which are considered particularly damaging to arterial walls. Because it integrates two routine laboratory measurements into a single number, AIP has become an increasingly popular surrogate marker in epidemiological studies of cardiovascular risk, especially in settings where advanced lipoprotein testing is unavailable.

Beyond AIP, the study examined five correlated secondary indices that capture complementary dimensions of metabolic dysfunction. The triglyceride-glucose index, or TyG, is a simple proxy for insulin resistance computed from fasting triglyceride and glucose values. The Lipid Accumulation Product, or LAP, combines waist circumference with triglycerides to estimate lipid overaccumulation in central depots. A Body Shape Index and the Body Roundness Index use waist measurements alongside height and weight to estimate the risk conferred by central adiposity beyond what body mass index alone reveals. Finally, the Visceral Adiposity Index, or VAI, integrates body mass index, waist circumference, triglycerides, and HDL cholesterol into an indirect estimate of visceral fat dysfunction. Together, these indices map glycemic, atherogenic, and adiposity-related pathways of cardiometabolic risk.

The results were consistent across the board. Participants in the highest tertile of diet quality had lower body mass index, smaller waist circumferences, lower fasting blood glucose, lower triglycerides, lower liver enzymes, and lower values on the cardiometabolic risk indices than participants in the lowest tertile. Lower circulating liver enzymes, including alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyl transferase, are often interpreted as indicators of reduced hepatic fat accumulation and better liver health, which is itself tightly connected to insulin sensitivity and lipid metabolism.

In the primary adjusted statistical model, which controlled for age, sex, education level, smoking status, physical activity, and total energy intake, the highest versus lowest LLDS tertile was associated with a lower AIP, with an unstandardized regression coefficient of -0.041 and a 95 percent confidence interval spanning -0.063 to -0.019, a difference that reached statistical significance at P less than 0.001. Inverse associations were also observed for TyG, LAP, ABSI, BRI, and VAI, meaning that better diet quality tracked with lower values on every one of the secondary indices examined. The consistency of direction across markers that tap into different physiological pathways strengthens the plausibility of a genuine relationship between overall dietary pattern and cardiometabolic health in this population.

The investigators also ran a clinical sensitivity analysis, designated Model 3, which added baseline clinical-status variables and medication use to the adjustment set. In this more conservative model, the inverse association between diet quality and AIP persisted, with an unstandardized coefficient of -0.036 and a 95 percent confidence interval of -0.058 to -0.014, and a P value of 0.001. The fact that the association survived additional statistical control for clinical conditions and medications suggests that the relationship is not simply an artifact of sick participants eating differently or taking lipid-lowering drugs, although sensitivity analyses in observational research cannot eliminate every possible source of confounding.

The authors are careful to note the central limitation of the work: because the design is cross-sectional, the associations observed do not establish temporal or causal relationships. It remains possible that people with healthier metabolic profiles find it easier to eat well, or that unmeasured characteristics such as income, food security, or psychological wellbeing simultaneously shape both diet and cardiometabolic health. Reverse causation is a perennial concern in nutritional epidemiology, and only prospective cohort studies or randomized interventions can determine whether improving diet quality actually lowers these risk indices over time. The study’s authors explicitly call for prospective research to establish the longitudinal and clinical significance of the findings.

Even with those caveats, the study adds a meaningful data point to a growing international literature on diet quality scoring. Iran faces a substantial burden of obesity and cardiometabolic disease, and dietary patterns in the region have been shifting toward higher intakes of refined carbohydrates, sugar-sweetened beverages, and processed foods. Demonstrating that a validated European diet quality metric behaves as expected in Iranian adults with excess weight provides a foundation for future longitudinal work in the region and for clinicians who wish to frame dietary counseling in terms of overall pattern rather than single nutrients. As surrogate markers such as AIP and TyG continue to gain traction as accessible windows into cardiovascular and metabolic risk, studies like this one help clarify which populations stand to benefit most from population-level improvements in the food environment and individual-level dietary change.

Subject of Research: Association between diet quality measured by the Lifelines Diet Score and cardiometabolic risk indices in overweight and obese adults

Article Title: Diet quality assessed by the Lifelines Diet Score and cardiometabolic risk indices in overweight and obese Iranian adults: implications for cardiometabolic physiology

Article References: Merza, M. Y. (2026). Diet quality assessed by the Lifelines Diet Score and cardiometabolic risk indices in overweight and obese Iranian adults: implications for cardiometabolic physiology. BMC Endocrine Disorders. https://doi.org/10.1186/s12902-026-02608-0

Image Credits: AI Generated

DOI: 10.1186/s12902-026-02608-0

Keywords: Lifelines Diet Score, diet quality, Atherogenic Index of Plasma, cardiometabolic risk, obesity, insulin resistance, TyG index, visceral adiposity, nutritional epidemiology, Iran, cross-sectional study, triglycerides