The purpose of this study is examine the effect of different fat types on postprandial glucose control in patients with type 1 diabetes.

Subjects will have several admissions and, in random order, will receive lunches with identical carbohydrate content but different fat content: lunch A will minimal fat content, lunch B will contain added butter, lunch C will contain added olive oil, and lunch D will contain added cheese. Total fat content in lunches B-D will be the same. Subjects will receive identical insulin doses (calculated using the subject's usual insulin-to-carbohydrate ratio) for the meals.

The investigators hypothesize that, despite identical carbohydrate content,the lunches higher in saturated fat will lead to more postprandial hyperglycemia than the lunch containing minimal fat and the lunch high in monounsaturated fat.

The hypothesis is that from time points 0-180 minute area under the curve for Lunches A, B, C, and D will be the same, whereas from time points 180-360 minutes for Lunch B and D will be greater than that of Lunch A and C.

Subjects for this study will be adults with type 1 diabetes who use insulin pump in their diabetes self-management. Prior to admission the the clinical research center the basal rates and insulin-to-carbohydrate ratio of the subjects will be optimized using standard clinical procedures.

Subjects will be admitted to the clinical research center in mid-morning following a light breakfast at home. Subjects will have several admissions and, in random order, will receive lunches with identical carbohydrate content but different fat content: lunch A will minimal fat content, lunch B will contain added butter, lunch C will contain added olive oil, and lunch D will contain added cheese. Total fat content in lunches B-D will be the same. Subjects will receive identical insulin doses (calculated using the subject's usual insulin-to-carbohydrate ratio) for the meals. Blood samples for measurement of plasma glucose and insulin levels will be drawn for the subsequent 6 hours. We hypothesize that postprandial glucose levels 3-6 hours after start of the meal will be higher following lunches B and D, compared to lunches A and C.

Inclusion Criteria:

• Adult patients (aged 18-75 years) with type 1 diabetes > 3 years.
• On insulin pump therapy.
• A1c < 8.5%.

Exclusion Criteria:

• History or symptoms suggestive of gastric dysmotility, celiac disease, pancreatic exocrine dysfunction or other conditions that cause malabsorption or maldigestion.
• Eating disorder.
• Diet allergies.
• Special diet restrictions, such as vegan or any nut allergy.
• Medications know to affect insulin sensitivity (such as glucocorticoids) or affect gastrointestinal motility (such as reglan).
• High-titre insulin autoantibodies with delayed insulin kinetics.
• Women who are breast feeding, pregnant, or wanting to become pregnant.