The purpose of this study is to investigate the short-term effects of a reduced fat plant-based diet on biomarkers of inflammation, oxidative stress and cardiovascular risk. This plant-based diet consists of whole grains, fruits and vegetables and little amounts of nuts and seeds, with no limitations on the amount of food intake. Animal products are not allowed. The results of the plant-based diet will be compared with the diet recommended by American Heart Association. This diet also emphasizes fruits and vegetables, but allows healthy fats, low-fat meats, fish and low-fat dairy in moderation. The results of the study might be useful in understanding whether or not plant-based diets are protective against cardiovascular disease.

Scientific Question: In obese, hypercholesterolemic (>169 mg/dl) 9-18 year olds and one of their parents are biomarkers of inflammation, oxidative stress and cardiovascular risk significantly reduced after a randomized 4 week trial of a reduced fat, vegan diet, or the American Heart Association (AHA) diet (which also encourages fruits, vegetables and whole grains, but permits low fat meat and dairy, and fish)? Rationale: "Cardiovascular disease remains the leading cause of death in North Americans, but manifest disease in childhood and adolescence is rare. By contrast, risk factors and risk behaviors that accelerate the development of atherosclerosis begin in childhood, and there is increasing evidence that risk reduction delays progression toward clinical disease". Myeloperoxidase is an early biomarker of inflammation, oxidative stress and cardiovascular risk in prepubertal obese children and is over expressed in children with hypercholesterolemia. Trimethylamine N-oxide, global arginine bioavailability ratio, arginine methylation index, paraoxonase 1 gene, and F2-isoprostane are all also associated with future major adverse cardiovascular events. Studies have suggested that a low-fat, vegan diet is effective in promoting weight loss, lowering body mass index, improving lipoprotein profiles, insulin sensitivity and in preventing cardiovascular disease in overweight individuals. Vegetarian diets have been shown to not only prevent but also to reverse heart disease in adults. Dietary habits (e.g. vegan/vegetarian versus omnivore/carnivore) are associated with significant alterations in intestinal microbiota composition and function. The diet-microbe interaction may play a significant role in the cardiovascular protective effects of a vegan/vegetarian diet. One small report of 15 adults on a reduced fat, vegan "Engine 2 Diet" for four weeks reported decreases in mean total cholesterol from 197 mg/dl to 135 mg/dl and mean LDL cholesterol falling from 124 mg/dl to 74 mg/dl.

Innovation: This is the first randomized trial comparing a low fat vegan diet to the standard AHA diet. If one diet proves superior in this brief pilot study, future larger long term studies will be needed to clearly define the health implications of our results.

Methods: Obese hypercholesterolemic children ages 9-18 will be identified by reviewing medical records and recruited initially by letters. Child, parent/guardian pairs will be randomly assigned to either the reduced fat vegan diet or the AHA diet.

During the 4-week study, participants will be asked to attend a group teaching and cooking session once a week on Saturday to learn about their assigned diets. The participants will also be requested to record their diet history on 2 weekdays and 1 weekend day before and again during the 4 weeks of the study.

Inclusion Criteria:

• Children ages 9-18
• BMI > 95th percentile
• Hypercholesterolemia (>169 mg/dl)

Exclusion Criteria:

• Pregnant women
• Patients already on vegetarian diets