I like how true-to-life this is. Most any girl can relate to it, as most are always looking to lose weight or are at least on a diet. Megan seems very realistic as well.

I just wanted to point out a couple of things. Most BMI readings aren't really "overweight" until you hit 30...I believe. At least most doctors don't really worry about it. I've been at 28 before and have never been close to hitting 178 pounds. Of course, every body is different too. Just thought I would mention it if you want to revise the numbers at some point.

Overall, you have a very promising first chapter!