Obesity, metabolic syndrome, and type-2 diabetes mellitus are common in Muslim patients living in Germany, most of whom are of Turkish origin. Lifestyle interventions must be tailored to religion and ethnicity. We tested the body weight-reducing effect of a 30% calorie-reduced intake diet, adjusted to individual energy expenditure, eating habits, and food preferences in a Turkish-background cohort. Eighty subjects were randomized to activity advice only or to a step-count device to monitor and document physical activity before and after the 12-week intervention. Fifty-three patients completed the study. Lifestyle interventions were effective in these Muslim subjects. Body weight was reduced by 6%; activity monitoring provided a modestly increased effect to 8%. Blood glucose, HbA1c, triglycerides and cholesterol improved also substantially. Subjects receiving metformin could reduce their dosage. Our data show that Muslim Turkish patients respond to interventions if these are tailored to their needs.