The purpose of the study is to evaluate the safety of short-term (6 month) low or very-low carbohydrate diets in prepubertal children 2 to <12 years old with type 1 diabetes. Participants will be randomized to either low carbohydrate diet (carbohydrate makes up 30-39% of total daily calories) or very-low carbohydrate diet (carbohydrates are 20-29% of total daily calories). The investigators will evaluate metabolic effects of these diets by measuring the counter-regulatory hormone response to hypoglycemia at baseline and again at 3 months. Other outcomes include diabetes control as measured by HbA1c, growth and weight gain, lipid profiles, and body composition.

The purpose of the study is to evaluate the safety of short-term (6 month) low or very-low carbohydrate diets in prepubertal children 2 to <12 years old with type 1 diabetes. Participants will be randomized to either low carbohydrate diet (carbohydrate makes up 30-39% of total daily calories) or very-low carbohydrate diet (carbohydrates are 20-29% of total daily calories). The investigators will evaluate metabolic effects of these diets by measuring the counter-regulatory hormone response to hypoglycemia at baseline and again at 3 months. Other outcomes include diabetes control as measured by HbA1c, growth and weight gain, lipid profiles, and body composition.

Participants will be admitted to the Clinical Research Center at baseline and 3 months. Gradual reduction in serum glucose to under 80 mg/dL will be achieved by an increase in their insulin infusion rate through their insulin pump. Plasma glucose, catecholamines (epinephrine, norepinephrine), glucagon, and serum ketones are measured at baseline and after glucose is below 80 mg/dL. All subjects will have lipid evaluation and body composition (DXA scan) at baseline and 6 months. Subjects' growth will be evaluated by comparing their height and weight z-score before and after the 6 months of diet intervention. Change in growth velocity will also be assessed. During the study, participants not already using continuous glucose monitoring will be placed on Dexcom G5 to monitor blood sugars regularly. Subjects will also be monitoring serum ketones at home regularly.

Inclusion criteria

• Prepubertal children 2 to <12 years old (i.e., before 12th birthday)
• Type 1 diabetes for at least 6 months
• Patients must be using insulin pump therapy
• Not presently on low carbohydrate diet

Exclusion criteria

• On low or very low carbohydrate diet
• History of endocrine or metabolic disorder that could affect counter-regulation (well-controlled hypothyroidism is acceptable if on stable dose of l-thyroxine for ≥3 months)
• History of metabolic disorder affection lipid metabolism
• Severe hypoglycemic event in past 3 months