Pencil Thin

I have the hardest time with yoga and pilates–I do them here and there and don’t feel like they are doing anything! My sister, who is in awesome shape, swears that anytime she hits a plateau this really jump starts her metabolism again. I am doing all kind of work out videos and loving them but wonder if I should incorporate yoga in here? I have pilates videos and they really hurt my neck no matter how I try to do them which has me wondering if yoga would be a better option. I want you to tell me your stories and opinions! I am trying to boost my metabolism and have a healthy heart. I do not need to exercise to burn lots of calories but just need my metabolism to START! I am always open to other workout ideas if you have any you want to share.