Rising obesity and shifting disease patterns in Saudi Arabia: a nine-year population-based analysis of chronic disease burden and multimorbidity profiles

Obesity represents a major and growing public health challenge in Saudi Arabia and is commonly accompanied by a broad range of chronic conditions. Understanding population-level changes in body mass index (BMI) distribution and associated disease burden over time is important for surveillance and health system planning. This study aimed to describe temporal trends in BMI categories and examine their associations with chronic disease burden among adults in southern Saudi Arabia over a nine-year period. We conducted a retrospective cohort study using electronic health records from the Armed Forces Hospitals Southern Region between January 2017 and April 2025. The dataset included 74,881 adult patients with a total of 956,547 visit entries. Body mass index (BMI) was calculated and categorized based on World Health Organization criteria. Chronic conditions such as type 2 diabetes, hypertension, heart failure, asthma, and others were identified from diagnosis records. Multivariable logistic and negative binomial regressions were used to evaluate the association between BMI and disease risk. Latent class analysis was performed to identify distinct multimorbidity profiles. Nearly half of the study population fell into obesity categories, with 26.6% in class 1, 13.3% in class 2, and 6.5% in class 3. Obesity rates rose consistently over the study period. Higher BMI was strongly associated with increased odds of chronic diseases. Compared to individuals with normal BMI, those in obesity class 3 had 2.47 times the odds of type 2 diabetes and 2.60 times the odds of hypertension. Multimorbidity also rose with BMI, and age was a significant independent predictor. Latent class analysis revealed three distinct disease profiles, with the most burdened group being older and having the highest average BMI. In this large healthcare-based population, obesity prevalence increased over time and was associated with a graded burden of chronic disease and multimorbidity. Associations varied by age and sex, highlighting heterogeneity in obesity-related disease patterns. Although causal inferences cannot be drawn, these findings provide important population-level evidence to support ongoing surveillance and the development of age- and sex-responsive prevention and clinical management strategies in Saudi Arabia and similar settings.