QUOTE : A meta-analysis of four cohort studies following the diets, diseases, and deaths of more than a quarter million people found that those who eat lower-carb diets suffer a significantly higher risk of all-cause mortality, meaning they live, on average, significantly shorter lives.4188 The risk of cardiovascular disease specifically appears to depend on the source of fat. In a Harvard study of heart attack survivors, those who adhered more to a lower-carb diet based on animal sources of fat and protein had a 50 percent higher risk of dying from a heart attack or stroke, but no such association was found for lower-carb diets based on plant sources.4189 These studies were based on low-carb scoring systems, though, so they speak more to the risks of lower-carb eating rather than a truly low-carb ketogenic diet.