A 2015 study in the Journal of the American College of Cardiology found that 76 people who followed the Paleo diet for 60 days (as well as those who followed vegan, Mediterranean and DASH plans for the same length of time) lost an average of 9 pounds and showed improvement in their blood pressure levels. The effects were greatest and most sustained among people who also attended regular diet support group meetings.
Another downside: If you have had chronic health issues (especially gut related), you may find that reintroduction actually teaches you that you're sensitive to most foods. It turns out peanut butter, gluten, and most dairy are now off limits. That rots!! But I'll live. I feel so, so much better without them, as I learned. And wouldn't you rather know why you feel crappy all the time?

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.”