I was 6 foot 1 but 170 to 175. For 9 years my weight never changed back and forth more than 3 - 5 pounds. Even though I have ran serious for the past 7 years, high school/college and post college, the weight never changed until working 40 hour weeks outside this past couple months and 15 hours in a hot kitchen at a restraunt.
I now weigh 158 - 162 and am running about 110 a week. Personally I am glad for the change. I eat and drink enough to nutritionally I am fine. Don't waste your money on protein powder if you don't have to. You are at a good running weight for your height, be happy for that. If you are not a serious runner than suck up plenty of protein. From what I have heard you shouldn't take more than about 30 grams of protein at a time, otherwise you are just wasting it due to your body not being able to take it in.
Stay hydrated. Good luck.