Aim: This study aimed to assess whether group-based lifestyle counselling offered to a high-risk population subgroup had any effect beyond individual multifactorial interventions on fasting plasma glucose (FPG) and 2-h plasma glucose (2hPG) changes. Methods: In a population-based study of 6784 participants, 4053 were determined to be at high risk based on a risk estimate of ischaemic heart disease or the presence of risk factors (smoking, hypertension, hypercholesterolaemia, obesity, impaired glucose tolerance). Of these subjects, 90% were randomized to high-intensity intervention (group A) and 10% to low-intensity intervention (group B). All participants went through health examinations, risk assessments and individual lifestyle counselling. Participants in group A were further offered group-based lifestyle counselling. The intervention was repeated after 1 and 3 years. A total of 2738 participants free of diabetes at baseline (1999-2001) and with at least one FPG and/or 2hPG measurement during 5 years of follow-up were included in the analyses. Differences in changes of plasma glucose between groups A and B were analyzed using multilevel linear regression. Results: For FPG, crude 5-year changes were significantly different between the two groups (group A: -0.003 mmol/L vs group B: -0.079 mmol/L; P= 0.0427). After adjusting for relevant confounders, no differences in FPG changes were observed (P= 0.116). Also, no significant differences in the 5-year changes in 2hPG between the two groups were observed (group A: - 0.127 mmol/L vs group B: -0.201 mmol/L; P= 0.546). Conclusion: Offering additional group-based intervention to a high-risk population subgroup had no clinical effects on changes in plasma glucose beyond those of individualized multifactorial interventions.