Vegan diet, processed foods, and type 1 diabetes: A secondary analysis of a randomized clinical trial.

Background and aims: Plant-based diets lead to weight loss and improved insulin sensitivity. However, some plant foods are highly processed, raising the question as to their effect on body weight and insulin sensitivity.

Methods and results: Fifty-eight adults with T1D were randomly assigned to an ad libitum low-fat vegan (n = 29) or a portion-controlled group (n = 29) for 12 weeks. Three-day dietary records were analyzed using the NOVA system, which categorizes foods from 1 to 4, based on degree of processing. A repeated measure ANOVA, Spearman correlations, and a linear regression model were used for statistical analysis. In the vegan group, the consumption of animal foods decreased in all categories, significantly so in categories 1, 2, and 4. Animal foods in category 1 decreased in the vegan group; effect size: -192 g/day (95 % CI -297 to -88); p < 0.001. Concomitantly, the intake of plant-based foods in category 1 increased in the vegan group; effect size: +334 g/day (95 % CI -24 to +693); p = 0.07. No significant changes were observed in plant-based foods in categories 2, 3, and 4 in either group. Changes in animal foods in category 1 were positively associated with changes in body weight (r = +0.52; p = 0.001) and negatively with changes in insulin sensitivity (r = -0.46; p = 0.005). A 140-g/day reduction in the consumption of animal foods in category 1 was associated with a 1-kg weight loss.

Conclusions: These findings suggest that replacing animal products with plant-based foods may be an effective weight-loss strategy in people with type 1 diabetes, even when processed foods are included.

Trial registration: ClinicalTrials.gov number, NCT04944316.