The purpose of this study is to determine if an exposure to light in the morning has a positive influence on self-chosen exercise intensity on a bicycle ergometer in overweight and obese patients.

Inclusion Criteria:

• Body Mass Index 25 - 35 kg/m2

Exclusion Criteria:

• Women who are pregnant or breast feeding,
• Other clinically significant concomitant disease states (e.g., renal failure, hepatic dysfunction, cardiovascular disease, etc.),
• Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant
• Previous enrolment into the current study
• Participation in other studies in the last four weeks
• Systolic blood pressure > 170 mmHg, diastolic blood pressure > 100 mmHg
• Shift work in the last two months
• Travels across time zones in the last four weeks
• Use of photosensitisation drugs
• Clinical manifest depression
• Cardiovascular diseases which reduce age-appropriate exercise capacity