Inclusion criteria:  Type 1 diabetes Men and women ≥ 18 years of age Stable insulin regimen for past 3 months  Exclusion criteria:  Type 2 or gestational diabetes Body mass index ≥ 40 kg/m2 HbA1c ≥ 12.0% Smoking or drug abuse during the past six months Alcohol consumption of more than 2 drinks per day or the equivalent, episodic increased drinking (e.g., more than 2 drinks per day on weekends), or a history of alcohol abuse or dependency followed by any current use Unstable medical or psychiatric illness Already following a low-fat vegan diet Pregnant or breastfeeding, or plans of pregnancy within the study period Lack of English fluency Unable or unwilling to participate in all components of the study Evidence of an eating disorder