Interesting article. Doesn't mention 5:2 specifically, but follows same program. Washington University is a very well thought of for their medical studies in the US.

http://www.stltoday.com/lifestyles/health-med-fit/health/will-fasting-help-you-lose-weight-live-longer-wash-u/article_b9859e45-f825-5f4f-ab79-a05223120e91.html