Why can't people just be happy for me?

So I'm trying to lose weight. I've been telling my friends to let them know and to seek encouragment and motivation. They ask what I'm doing. And what I'm doing is eating right and working out by running and light weight lifting. I've been told this is the best way for me to lose weight.

And according to my friends I'm doing everything all wrong. That it doesn't matter what I eat. Or I need to ONLY do cardio. But I think what I'm doing is the going down the right path but everyone has such a big head, they telling me it's wrong and I need to do what they think is right.

Why can't people just be happy for me?

Do I need better friends?