Importance: Diet and exercise represent the mainstays of obesity treatment. No systematic review has been conducted comparing the effect of dietary and exercise intervention in reducing metabolic risks in overweight children. Objective: To compare the effects of diet-only intervention with those of diet plus exercise or exercise only on weight loss and metabolic risk reduction in overweight children. Evidence Review: English-language articles from 1975 to 2010 available from 7 databases were reviewed. One person searched the databases. Two independent reviewers assessed abstracts and articles against the following eligibility criteria: randomized controlled trials conducted in overweight and obese children aged 18 years or younger, comparing dietary intervention with a diet plus exercise program or an exercise-only program. Study quality was critically appraised by 2 reviewers using established criteria. The main outcome measures were body mass index, body fat percentage, lean body mass, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, fasting glucose, and fasting insulin. Findings: Fifteen studies were identified and included. Based on the small number of short-term trials currently available, both diet-only and diet plus exercise interventions resulted in weight loss and metabolic profile improvement. However, the addition of exercise to dietary intervention led to greater improvements in levels of high-density lipoprotein cholesterol (3.86 mg/dL [to convert to millimoles per liter, multiply by 0.0259]; 95% CI, 2.70 to 4.63), fasting glucose (−2.16 mg/dL [to convert to millimoles per liter, multiply by 0.0555]; 95% CI, −3.78 to −0.72), and fasting insulin (−2.75 μIU/mL [to convert to picomoles per liter, multiply by 6.945]; 95% CI, −4.50 to −1.00) over 6 months. The diet-only intervention caused greater reductions in levels of triglycerides (at the end of active intervention) and low-density lipoprotein cholesterol (at subsequent follow-up). Conclusions and Relevance: This review provides insights into the impact of dietary and exercise interventions on metabolic risk reduction in the pediatric population. However, further studies are required to confirm the evidence with rigorous design, appropriate sample size, longer duration of follow-up, and better strategies to improve compliance and achieve long-term sustainability.