You make a fair point on the quality of the research technique. I did skim through the study and conclusions and don't deny double blind randomized control trials are historically the golden standard of scientific evidence (http://ebm.bmj.com/content/early/2016/06/23/ebmed-2016-11040...). Other randomized control trials have found polyunsaturated fat in place of saturated fat reduces Coronary Heart Disease events (see this meta-analysis of 8 randomized control trials, n=13,000+ http://journals.plos.org/plosmedicine/article?id=10.1371/jou...).
It's no doubt an interesting study and makes me question recommendations to consume oils. Still, based on current scientific evidence, there is good reason to be cautious about consuming more butter / saturated fats as is being advocated in numerous comments on this thread. As a reminder to those reading, there is strong evidence to supports nuts are a much better source of fat for health than both oils and saturated fat. Here's a meta-analysis of two cohort studies of 110,000+ that found nut consumption is inversely associated with total and cause-specific mortality (http://www.nejm.org/doi/full/10.1056/NEJMoa1307352).
It's no doubt an interesting study and makes me question recommendations to consume oils. Still, based on current scientific evidence, there is good reason to be cautious about consuming more butter / saturated fats as is being advocated in numerous comments on this thread. As a reminder to those reading, there is strong evidence to supports nuts are a much better source of fat for health than both oils and saturated fat. Here's a meta-analysis of two cohort studies of 110,000+ that found nut consumption is inversely associated with total and cause-specific mortality (http://www.nejm.org/doi/full/10.1056/NEJMoa1307352).