Inclusion Criteria:  Diagnosis of type 1 diabetes for at least 1 year Hemoglobin A1c level < 10% within the past 2 months Provision of signed and dated informed consent form by the adult (if person is at least 18 years old) or parent and assent form if the participant is <18 years old. Stated willingness to comply with all study procedures and availability for the duration of the study Male, female, transgender, nonbinary are all eligible Diagnosis of type 1 diabetes for at least 1 year Insulin pump use for at least 2 months. Ability to perform daily blood ketone checks, wear a continuous glucose monitor, willing to wear an activity monitor, willing to adhere to the study diets and keep a diet journal. For females of reproductive potential: use of highly effective contraception for at least 1 month prior to screening and agreement to use such a method during study participation and for an additional 4 weeks after the end of the dietary intervention. For males of reproductive potential: use of condoms or other methods to ensure effective contraception with partner  Exclusion Criteria:  Current use of glucose-lowering agents other than insulin Unstable psychiatric disorders, including eating disorders Weight loss medications within the last 6 months Pregnancy or lactation, or planning pregnancy within the next 6 months BMI < 19 kg/m2 for individuals 18 years of age or older BMI < 5%ile for individuals under 18 years Weight less than 49 kg or 108 pounds Other medical conditions that may interfere with glucose metabolism and insulin sensitivity