This study will investigate whether growth hormone is modulated by the enzyme SIRT1 and by that is stimulating lipolysis on expense of IGF-I production. This is done in 10 healthy men on calorie restriction on 4 study days with fat and skeletal muscle biopsies.

It has been shown that calorie restriction enhances the length of life in yeast, worms, fish and rodent. Whether this elongation of life due to calorie restriction can be applied to humans is not known. However, it is a fact that calorie restriction will decrease the risk of developing metabolic disturbances such as diabetes, hypertension and atherosclerosis.

On the molecular level the specific relations are not fully understood. This study will investigate the possible connection between SITR1 and the relation to the GH/IGF-I axis and STAT5b in healthy men. The participant will fast 42 and 12 hours respectively, and have GH or placebo infusions. The design is a classical 2x2 design and will be randomized.

Knowledge of the interactions between calorie restriction, SIRT1, STAT5b and the GH/IGF-I axis will apply important information about the relations between aging, energy metabolism and metabolic disturbances.

Inclusion Criteria:

• healthy lean men
• age >18

Exclusion Criteria:

• metabolic disturbances
• alcohol drug abuse
• malign disease: current or previous