While there is wide variability in the way the paleo diet is interpreted, the diet typically includes vegetables, fruits, nuts, roots, and meat and typically excludes foods such as dairy products, grains, sugar, legumes, processed oils, salt, alcohol, or coffee.[additional citation(s) needed] The diet is based on avoiding not just processed foods, but rather the foods that humans began eating after the Neolithic Revolution when humans transitioned from hunter-gatherer lifestyles to settled agriculture. The ideas behind the diet can be traced to Walter Voegtlin,:38 and were popularized in the best-selling books of Loren Cordain.
The WHO trial (so named because the international team of principal investigators contained World Health Organization members) tested the potential of clofibrate, a “pre-statin” cholesterol-lowering agent, to reduce heart attack morbidity and mortality. The investigators ultimately concluded that clofibrate "cannot be recommended as a lipid-lowering drug for community-wide primary prevention of ischaemic heart disease.” Nevertheless, clofibrate remained in use until 2002, when it was pulled for increasing cancer rates. In their review of studies such as the WHO trial, Uffe Ravnskov and David Diamond observe, “Despite the largely disappointing findings from 50 years of cholesterol lower[ing] trials, the indictment and conviction of cholesterol as the causal agent in CVD [cardiovascular disease] has stood the test of time. … [Yet] the grand effort to reduce cholesterol as a strategy to improve health has failed.”