The purpose of this study is to characterise beta cell function in subjects who despite taking part in a diabetes prevention program (life style intervention with diet and exercise) exhibit impaired glucose tolerance and beta cell dysfunction.

We have identified a subgroup of individuals with a good compliance to lifestyle intervention to prevent diabetes who lose body weight and increase insulin sensitivity, however they remain impaired glucose tolerant. These individuals show a deterioration in insulin secretory function.

We will identify a highly selected group of subjects with prediabetes that displays a large defect in insulin secretory function.We will study 50 individuals who display these characteristics and 50 subjects who do not display these characteristics. Their insulin secretion capacity in response to different secretagogues (glucose, GLP-1, arginine) will be studied. We expect to detect new pathophysiologic aspects that lead to beta cell failure particularly in this group.

Inclusion Criteria:

• Impaired glucose tolerance
• BMI 16-40 kg/m²

Exclusion Criteria:

• chronic disease
• anemia
• therapy with insulin or cortisone