Having trouble staying dedicated without immediate results

Hey guys!

I know weight loss isn't an immediate thing, and improving your health isn't an immediate thing. But I guess one of my biggest faults is that I *love* instant gratification. I've tried to lose weight before, and even if manage to lose a few pounds, when a few weeks go by and I don't notice my clothes fitting well (or...sometimes I actually feel bigger after a few weeks of working out) I get incredibly discouraged and usually just stop.

I want to lose weight. I want to run a marathon. Right now my BMI is on the high-end of normal. My body fat percentage is about 30%, which is also the high end of "normal" (or at least I think so?). I'm just trying to lose maybe 20-25 pounds of fat? Even less would be fine. I just want to be healthy.

I've been seeing a nutritionist, and I think my diet has improved a lot (green smoothies, more protein, less sugar!) but I always forget about water.

What do I do when I can't stay motivated or on track? I do have a history of disordered eating, and it's so easy to just not eat for a few days and see that I've lost three pounds (I know it's not healthy, I know they come right back, that's not what I'm trying to do here). How do I stay on track, MFP? How do I FINALLY change my lifestyle for the better, and get on track to becoming healthier?