The study is a year-long health-behaviour intervention in obese, male truck-drivers to lose weight moderately by 10%, using monthly individual counseling. The investigators hypothesize that lifestyle modification (increased physical activity, changes in eating habits, and improved schedule for sleep) through weight loss improves daytime alertness and quality of sleep, reduces daytime sleepiness, and improves cardiovascular risk factors and health-related fitness.

Daytime sleepiness, i.e., being fatigued at work is an important risk factor for traffic accidents involving commercial vehicles. Sleep-related disturbances and daytime fatigue may be partly related to obesity, which is common among truck drivers. This study is a randomised 12-month health-behaviour intervention in obese, male truck-drivers. We hypothesize that lifestyle modification (increased physical activity; decreased energy intake; and improved schedule for sleep), aimed to reduce weight moderately by 10%, improves daytime alertness and quality of sleep, reduces daytime sleepiness, and improves cardiometabolic health and health-related fitness. The primary aim is weight loss. We will recruit 140 participants aged 30-62 years and with abdominal obesity. The participants are randomised into an intervention (INT) and control (CON) group, for 12 months. The INT group gets individual lifestyle counseling monthly. After 12 months, the CON group receives weight-loss counseling for 3 months. Assessments (psychological vigilance test, sleep duration, dietary intake, physical activity, metabolic syndrome, health-related fitness) take place at months 0, 12 and 24. We expect to develop counseling strategies (leading to weight loss through changes in lifestyle) that can be used to improve sleep, alertness and cardiometabolic health in occupational health care.

Inclusion Criteria:

• male
• age 30-62 years
• long-distance truck or bus driver (on average continuous driving for at least one hour daily outside the city center)
• irregular working hours (on average at least once weekly between 0600-1800 hours)
• waist circumference at least 100 cm
• sedentary: leisure physical activity no more than 30 minutes twice weekly at moderate intensity, and no medical contraindications to increase physical activity

Exclusion Criteria:

• no moderate or severe sleep apnoea with CPAP therapy or with previous surgical operations in the neck area (e.g., UPPP)
• no regular use of sleeping medicines (on average not more often than once weekly)
• no severe sleep disorder
• greatly elevated resting blood pressure (> 180/120 mmHg)
• no diabetes mellitus with medication