Association between ultra-processed foods and adiposity: findings from a Tehran lipid and glucose study

A few cohort studies have assessed the relationship between ultra-processed foods (UPFs) and obesity; however, there is a knowledge gap about adiposity. We designed the present cohort study to investigate the relationship between UPF consumption and adult adiposity. The adiposity indices considered in the present study included: waist circumference (WC), WC-to-height ratio (WHtR), Clínica Universidad de Navarra-Body Adiposity Estimator (CUN-BAE) index, body roundness index (BRI), a body shape index (ABSI), and visceral adiposity index (VAI). This cohort study included 2734 adults from the Tehran Lipid and Glucose Study (TLGS). Five measurements were available at the baseline (2006-2008) and every three years until the end of follow-up (2018-2023). We applied the NOVA food classification to estimate our population's consumption of UPFs in servings per day. We used mixed linear regression to assess the association between the tertiles of UPFs as servings per day and changes in adiposity indices. The dose-response relationship between UPFs (serving per day) and outcomes was determined using a restricted cubic spline model. The mean age of participants was 39.8 years, and 54.1% were women. The median follow-up time was 11.9 years. The results of linear mixed models demonstrated a positive relationship between consumption of UPFs and weight (β = 0.17, P < 0.0001), body mass index (BMI) (β = 0.05, P = 0.002), CUN-BAE index (β = 0.08, P < 0.0001), WC (β = 0.16, P = 0.001), BRI (β = 0.02, P = 0.02), WHtR (β = 0.001, P = 0.005), and ABSI (β = 0.00006, P = 0.003) in the full model. There was no association between UPFs and the VAI (β = 0.01, P = 0.55). In the dose-response analysis, the association increased significantly after five servings per day. When we considered changes in each outcome per year, we found that the annual increases in weight by 0.12 kg, BMI by 0.04 kg m^-2, WC by 0.12 cm, CUN-BAE index by 0.06 unit, BRI by 0.02 unit, and WHtR by 0.001 unit were greater in the third tertile of UPFs compared with the first tertile. Our results support the positive association between UPFs and adiposity indices.