The internal arm-wrestling match. Strangers and acquaintances are not the only people who treat the newly fit person differently. You may find your relatives and friends treat you differently as well. I'm jealous because you've done it, and I can't. They may view they way you keep yourself well as self-centered and narcissistic.
Family members can also have trouble dealing with a dramatic physical change.
My kids think I'm a fanatic. Family members can have the same issues as friends, but being healthy and fit can get right to the roots of what holds your family together. For some families, being together means stuffing your face. Auntie doesn't understand why you want to go for a 30-minute walk after dinner rather than have dessert. Cousins and uncles may be disappointed that you don't want to stay for the football game.