The GOAL (Good Ageing in Lahti region) Program Life-style change implementation trial to prevent type 2 diabetes was set to examine and enhance the effectiveness of life-style change counselling in the primary health care. In the intervention, specific nutritional, physical activity and weight loss objectives shown effective in diabetes prevention in an earlier randomised controlled trial are used as a benchmark, embedded in a structured group counselling model with an empowerment-oriented approach and adapted into the primary health care setting. In the trial, effectiveness and process are evaluated, the analyses including gender and socio-economic differences. Participants were 361 middle-aged (50-65 yrs) adults at an increased risk for type 2 diabetes, recruited in 16 primary health care centres in Paijat-Hame, Finland. Intervention and data collection took place in year 2003.