Childhood obesity is associated with type 2 diabetes mellitus. We aimed to determine the effects of lifestyle modification programs on fasting plasma glucose (FPG) levels in overweight children. We queried six relevant electronic databases and manually searched for studies published before December 2016. Overweight/obese children who underwent a lifestyle modification for more than 6 months were included. A total of 3923 children from eight randomized controlled trials (RCTs) were included. Compared with the control group, the lifestyle modification group had significantly lower FPG levels by 1.3 mg/dL. The mean differences were significantly decreased for both secondary outcomes; BMI z-score decreased by 0.16 units and insulin levels decreased by 2.4 mU/L. The metaregression showed that the follow-up duration was associated with FPG levels and BMI and insulin levels and half year is a suitable follow-up duration for this population. This study showed that lifestyle modification programs may be effective in reducing the FPG levels of overweight/obese children. Further high-quality RCTs with longer follow-up periods are needed to evaluate the long-term effect of this complementary approach for diabetes mellitus prevention on overweight/obese children.