Using an animal model, the research team designed the study to mimic human Western- and Mediterranean-type diets that could be controlled and analyzed over a sustained period of time. Long-term diet studies involving people usually rely on self-reported dietary intake collected via questionnaires with nutrient intake only estimated.
Non-human primates were randomized to either a Western or Mediterranean diet. The Western diet consisted of lard, beef tallow, butter, eggs, cholesterol, high-fructose corn syrup and sucrose, while the Mediterranean diet consisted of fish oil, olive oil, fish meal, butter, eggs, black and garbanzo bean flour, wheat flour, vegetable juice, fruit puree and sucrose. The diets had the same number of calories.