help with the name of this book

[milewalker]

hi, I've been trying to find the name of a book I read while at secondary school (I can even remember the picture on the front but the name escapes me) so thought i'd ask incase any of you read it.
I remember it was about an overweight lady who decided to start jogging/running but she felt to big to do it during the day so did it evenings while wearing normal clothes and a raincoat and she carried a dog lead so if anyone saw her she could say her dog ran away (there was no dog)
further on in the book she travelled the world an ate chocolate covered bees. that's all I can remember but would love to read it again now.
I think of her quite often and wonder if she kept running. thanks in advance if anyone has any idea what this book is