Introduction: Insulin resistance has been proposed to accelerate progression to type 1 diabetes (T1D) in antibody positive relatives of affected individuals. We hypothesised that overweight individuals with confirmed T1D would be less likely to present with diabetic ketoacidosis (DKA), signifying an earlier onset of T1D, due to concomitant insulin resistance.

Methods: The ADDRESS-2 study recruits incident clinician-assigned T1D cases within 6-months of diagnosis and systematically assesses pancreatic autoimmunity by GAD-65, IA-2 and ZnT8 antibodies. People with at least two positive antibodies were selected to confirm diagnosis of T1D and categorised for adiposity according to BMI (adults) or Z-scores (children). Odds ratios (OR) for presentation with DKA were compared, adjusted for potential confounders and sub-analysed by whether adult or child at recruitment.

Results: 31% (969/ 3132) were positive for two or more pancreatic antibodies. Of these 44% (424/969) presented with DKA. The proportions with DKA varied significantly by adiposity: 59% underweight (16/27), 47% normal (280/601), 39% overweight (103/263), 30% obese (19/63) and 40% severely obese (6/15) (p=0.02). When adjusted for age, being overweight or obese was associated with lower risk of DKA in adults (OR 0.58, p=0.006; 0.44, p=0.03, respectively) not children (OR 0.9, p=0.81; 0.51, p=0.12, respectively). Higher adiposity category was associated with higher daily insulin-requirements independent of age, with obesity associated with a 4 unit/day increase (p=0.03) and severe obesity, 11 units/day increase (p=0.008).

Conclusion: Adults with T1D are less likely to present with DKA if overweight or obese. Despite smaller proportions of DKA, insulin requirements are higher. These data suggest that, in adults, T1D presentation is unmasked by the insulin resistance of obesity prior to absolute insulin deficiency and ketoacidosis.