The moderating role of central adiposity, sex and age, on the association between animal- and plant-based protein intake and the 20-year cumulative incidence of type 2 diabetes: the ATTICA cohort study (2002–2022)

PURPOSE: The aim of this study was to evaluate the role of central adiposity, sex and age, on the association between total-animal and total-plant based protein and the 20-year cumulative incidence of type 2 diabetes (T2D), among apparently healthy adults participating in the ATTICA cohort study (2002-2022). METHODS: The present analysis included data from 2,000 individuals free of atherosclerotic cardiovascular disease and T2D at baseline (age 43 ± 13 years; 51% women). Total, animal-based, and plant-based protein intake were measured, through a validated food frequency questionnaire. RESULTS: The 20-year cumulative incidence of T2D was 26.3% (95%CI [24.4, 28.3%]). Total red meat intake was consistently associated with increased incidence of T2D in both sexes, with RRs ranging from 1.08 to 1.11 per 30 g/day increment (p's < 0.05), after adjustment for confounders. Among females, a higher intake of animal-based protein was significantly associated with increased incidence of T2D (RR 1.24, 95%CI [1.04, 1.48]), with no significant associations among males. The adverse association between animal-based protein intake and T2D was strongest among females with increased WHR (RR 2.06, 95%CI [1.21, 3.49]); no significant association was observed in males, regardless of WHR status. Among younger females (< 65 years) with increased WHR, the association between animal-based protein and T2D incidence was equally strong (RR 2.06, 95%CI [1.21, 3.49]), and plant-based protein intake retained a highly significant protective association (RR 0.24, 95%CI [0.08, 0.68]). CONCLUSIONS: Long-term animal protein intake, especially red meat, increases the likelihood of developing T2D, particularly in women with central obesity; plant protein appears protective in metabolically vulnerable subgroups.