The blood glucose fluctuates greatly in T1DM patients, especially in the middle and late stages of the disease, and carbohydrate (CHO) is the main determinant of postprandial glucose response (PGR). Based on the previous investigation to understand how nutritional habits affect blood glucose control, we will conduct dietary intervention studies in T1DM patients to explore whether the adjustment of dietary pattern is beneficial to blood glucose control, and further explore the relevant mechanism through the detection of related metabolic indicators.

1. Main Objective: To evaluate the effect of changes of carbohydrate intake on glucose control in patients with type 1 diabetes.

1. Primary endpoint: difference of time in range (TIR) between the 2 groups.
2. Secondary endpoint:

1) difference of coefficient of variation (CV), mean amplitude of glycemic excursions (MAGE) , large amplitude of glycemic excursions (LAGE) between the 2 groups; 2) difference of change in HbA1c，GA，1,5-anhydroglucitol (1,5-AG) from baseline between the 2 groups; 3) difference of change in incidence of hypoglycemic events (%), severe hypoglycemia and nocturnal hypoglycemia events from baseline between the 2 groups; 4) difference of change in insulin dose (IU/kg/day) from baseline between the 2 groups.

2. Secondary objective: To explore the possible mechanism of dietary intervention to improve blood glucose control in patients with type 1 diabetes.

1. Effects of dietary intervention on intestinal microenvironment and microflora of type 1 diabetes patients;
2. Effects of dietary intervention on immune function of type 1 diabetes patients;
3. Effects of dietary intervention on metabolomics of type 1 diabetes patients.

Inclusion Criteria:

1. Those who agree to participate in the study and sign informed consent;
2. Diagnosis of type 1 diabetes mellitus (ADA2024);
3. Age of 18~70 years;
4. Dependent on exogenous insulin therapy, the treatment plan remains unchanged within 2 months (the type of insulin cannot be changed, and the dose can be adjusted according to plasma glucose);
5. Body mass index (BMI) of 18~25kg/m2;
6. HbA1c ≤11%;

Exclusion Criteria:

1. Honeymooners with type 1 diabetes mellitus;
2. Women who are pregnant or plan to become pregnant;
3. Patients who are vegetarians or are undergoing weight loss;
4. Patients who are users of oral hypoglycemic drugs (alpha-glucosidase inhibitors, DPP-IV inhibitors, etc.);
5. Patients who are users of glucocorticoids within 30 days;
6. History of severe food allergy;
7. Patients with acute complications such as DKA or HHS within six months;
8. Patients with gastroparesis, inflammatory bowel disease and other complications;
9. Patients with large albuminuria(albumin-to-creatinine ratio>34.09mg/mmol) and renal insufficiency(creatinine>200umol/L);
10. Patients with uncontrolled hyperthyroidism and hypothyroidism(Uncontrolled hyperthyroidism is defined as abnormal TSH and T4. Uncontrolled hypothyroidism is defined as TSH > 10mIU/L.);
11. History of heart disease, coronary heart disease and arrhythmia;
12. Serious of liver dysfunction (ALT or AST>3 times the upper limit of normal);
13. History of malignant tumors; History of tumors or surgeries affecting digestion and nutrient absorption; Patients with a history of benign tumors, which is judged by the physician to be not suitable;
14. Patients with uncontrolled other immune system diseases or uncontrolled infections;
15. Alcohol abuse, drug abuse, mental disorders or other conditions unfit to be an observer in drug tests;
16. Patients with any disease likely to interfere with study participation or evaluation.