The existing studies about weight loss are limited by small sample size, short duration (<6 months), focus on very low calorie diet program or surgically induced weight loss program only. However, none of them have applied lifestyle modification program (LMP) which emphasizes on long term lifestyle and behavior change. Therefore, the investigators plan to conduct a randomized controlled trial among Chinese OSA patients by comparing the efficacy of LMP against usual clinical lifestyle advice alone on the improvement of OSA symptoms.