"Fitness." Merriam-Webster.com. Merriam-Webster, n.d. Web. 28 Dec. 2013. <http://www.merriam-webster.com/dictionary/fitness>.
I don’t know what prompted you to send me the dumbest message I’ve received in at least 6 months, but nowhere in the Merriam-Webster dictionary definition of “fitness” do I find the word “skinny.” Even synonyms for the word “fitness” focus 100% on health attributes as opposed to size attributes. So I’m sorry if you have this deep seeded complex that refuses to allow you to accept that, from all standpoints of medicine, science, and flat out fact, fitness is irrelevant to body size. That really sucks for you that your brain is struggling to let you come to terms with that. However, it is also 100% not my problem.
tl;dr: Blow it out your ass.