The Surwit diet series is most often used for obesity and diabetes research. Using hydrogenated coconut oil (>99% saturated fat) as the main source of fat, these diets are somewhat unique in that they contain no fiber and have higher sodium levels compared to what is commonly found in purified diet formulas. The four diet series contains two high-fat (58 kcal%) and two low-fat (10.5 kcal%) diets, with sucrose and corn starch alternating as the main carbohydrate source.