This human dietary intervention study with a cross-over design aims to investigate the effect of two different diurnal patterns of meal composition on peripheral circadian clocks and energy metabolism in healthy men.

In this cross-over study, healthy male participants are randomly allocated to one of two study groups: In study group (A) participants consume isocaloric carbohydrate-rich meals (65% Carbohydrates; 20% Fat; 15% Protein) in the morning and fat-rich meals (35% Carbohydrate; 50% Fat; 15% Protein) in the evening for four weeks. After a washout-phase participants consume isocaloric fat-rich meals in the morning and carbohydrate-rich meals in the evening for another four weeks. Study group (B) receives the same interventions in the reversed order.

Inclusion Criteria:

• BMI between 22 kg/m² and 34,9 kg/m²
• Normal glucose tolerance determined in a 75g-oral glucose tolerance test
• Impaired fasting glucose determined in a 75g-oral glucose tolerance test
• Impaired glucose tolerance determined in a 75g-oral glucose tolerance test

Exclusion Criteria:

• Shift workers or history of shift work
• Men suffering from diseases or conditions that might influence the outcome of the study. Of special interest are diseases that influence body weight regulation (enteropathy, malabsorption, hepatopathy, renal disease, endocrine disorders, diabetes mellitus, eating disorders, heart disease etc.). Also men suffering from coagulopathy, apoplexy and myocardial infarction are excluded from the study.
• Men suffering from psychiatric disease
• Planned changes in physical activity during the study
• Participation in other clinical studies within the last three months
• Weight changes > 2 kg within 2 months prior to screening day
• Men unable to give an informed consent
• Men unable to engage in the dietary interventions
• Men following a special diet