Metformin and physical activity are often recommended as the first therapeutic agents to improve glycemic control for prediabetes and type 2 diabetes (ADA). It has been reported that metformin decrease plasma concentration of non-esterified fatty acids in patients with type 2 diabetes which might be associated with the inhibition of lipolysis in adipose tissue. However, the inhibition of lipolysis during physical exercise, would not be probably beneficial. Thus, the effect of metformin on lipolysis during exercise is investigated in this protocol. As the lipolysis regulation is often impaired in obese and diabetic patients, the healthy lean men were chosen for this pilot study. Glycerol will be analyzed as a measure of lipolytic rate in adipose tissue and in plasma. Lactate levels will be observed. Our findings should provide a new background about the combination of physical activity and metformin medication.