Combined lifestyle interventions (CLIs) that target both physical activity (PA) and diet have been shown to improve PA and health of adults who are overweight; however, optimal amount of guidance remains unclear. This study evaluated the effects of adding PA group sessions to a standard CLI in primary care in the Netherlands. 411 participants (BMI 34.5 ± 4.4 kg/m2) in thirty locations were randomised into a one year CLI or CLI+. CLI comprised individual meetings with lifestyle coach (LSC) and physiotherapist, and group meetings with dietician. PA group sessions were added in CLI+. Primary outcome was minutes of moderate to vigorous PA per week. Secondary outcomes of PA, diet and cardiovascular risk factors (i.e. waist circumference, HbA1c and blood pressure) were evaluated after 12 and 24 months with multilevel analyses. Data were collected from 2010 to 2015. Significant between-group effects were only found for waist circumference, which was significantly lower at twelve months in the CLI+ group (p = 0.011), no other between-group differences were found. Several within-group changes were significant. After participating in the intervention, walking time increased with 83 ± 35 min/week and 100 ± 38 min/week, and BMI decreased with 0.7 ± 0.3 kg/m2 and 1.5 ± 0.3 kg/m2 in CLI and CLI+ respectively (p < 0.001). Diet, HbA1c and systolic blood pressure changed favourably in both groups. Adding PA group sessions did not elicit added, sustained benefits. A programme with individual meetings with LSC and physiotherapist, and group meetings with dietician can be sufficient to facilitate a healthy lifestyle and reduce cardiovascular risk factors in a population with overweight.