This is my first pair of Fit Flops. My feet are medium width and these fit my foot exactly, so I agree with other reviews that say these are really only for medium or narrow feet. The "gym in a shoe" claim is ridiculous. I have noticed absolutely no difference from my regular slippers/flip flops on that front. I am disappointed b/c of course I so wanted it to be true that I'd be burning extra calories and/or feeling a burn walking around in these shoes. I over-pronate, but I don't really have too much trouble wearing other shoes. I was hoping these would help my recovery between runs by absorbing shock or something as I walk... so far no noticeable difference. I guess I already have pretty good posture, which I'm glad about, but really I have noticed no difference in my posture/how I hold myself wearing these shoes versus other shoes. They didn't require any "getting used to" to walk in or anything. So these shoes are cute and comfortable, but certainly not living up to the hype in my mind. Also, the strap hits the top of the foot pretty close to the ankle, and is a little tight. The tag says if it's TOO tight, it means you have high arches (which I do) and that this means the shoes don't fit properly and to size up or try another style. I don't think these are too tight for my high arches (my feet did not slip back in the foot bed as the tag warns may happen), but they are definitely snug. I think since they're leather they'll stretch a teeny bit and that will make them more comfortable. I'd consider getting another pair if they were on sale, this time knowing from experience that they are just regular comfortable slippers/flip flops and not something that will help tone my legs in some magical way.