This study evaluates the prevalence of gastric emptying (GE) in type 1 diabetic patients (DM1) free of chronic complications in comparison with a group of healthy control subjects. The investigators will also assess the relationship between GE and glucose control (HbA1c, postprandial glucose variability), gut peptide hormones (GLP-1, GIP, and ghrelin), and gastrointestinal symptoms.

In addition, in patients with delayed GE the investigators will investigate the effect of "tailored" pre-prandial insulin bolus administered by means of insulin pump in reducing postprandial glucose variability, evaluated through continuous glucose monitoring system.

Diabetic patients with a delayed GE will be studied in 2 separate occasions in euglycemic condition and under CGM. On both occasions, they will have to take a standard meal poor of lipids (rice 60 g; yellow squash 200 g; extra virgin olive oil 7 g; adult veal lean cuts 90 g; bananas 180 g; ordinary bread 75 g).

On the first occasion pre-prandial insulin will be administered as single bolus calculated on the basis of carbohydrate counting and each patient's insulin/glycaemic load.

On the second occasion the amount of pre-prandial insulin will be the same as the first one test but fractioned into a double-wave bolus. The "tailored" insulin bolus will be defined according to the individual pattern of GE, as follows:

• GE T1/2 121-180 min= 60% as bolus + 40% during following 2 h
• GE T1/2 >180 min= 40% as bolus + 60% during following 4 h Glycemic variability will be assessed by the means of Continuous Glucose Monitoring System and the following indexes of glucose variability will be calculated: number of hypoglycemic events, number of hyperglycemic events, standard deviation of glycemia, glycemia variation coefficient, mean range of daily glycemia, interquartile range, M value, mean amplitude of glycemic excursions (MAGE), low blood glucose index (LBGI), high blood glucose index (HBGI).

Inclusion Criteria:

• DM1;
• Use of insulin pump;
• Disease duration ≥ 3 years.

Exclusion Criteria:

• Presence of chronic complications of DM (including cardiovascular autonomic neuropathy);
• BMI ≥ 30 kg/m2;
• Presence of chronic diseases other than DM1;
• Diseases that interfere with GE;
• Medications that interfere with blood glucose homeostasis (except insulin) and GE.