The investigators will conduct a randomized clinical trial to evaluate the efficacy of Lovaza (formerly known as Omacor) in reducing triglyceride levels in youth ages 10-19 years old whose baseline triglycerides range from 150 mg/dl to 1000 mg/dl. Seventy subjects will be recruited at baseline and randomized to the treatment condition, Lovaza 4 grams/day for 6 months or the control condition, a corn oil placebo, 4 tablets a day for 6 months. Participants in both the treatment and control groups will receive the standard of care, which is dietary advice to follow a low, refined carbohydrate and low saturated fat diet that emphasizes increasing intake of fruits and vegetables and eating 2 servings per week of fishes rich in omega-3 fatty acids, consistent with the American Heart Association recommendations. The primary outcome will be change in fasting triglycerides from baseline to 3 months. The investigators hypothesize that patients who receive LOVAZA will have significantly greater reductions in plasma triglyceride levels when compared to patients on placebo at 3 months.