You and your site helped me identify a book a few years ago, and I’m hoping you can help again! I have a lot of details but can’t manage to search in a way that pulls up this book.
This book is from the 70s or 80s, I read it in probably the mid to late 90s. It was paperback and a realistic, contemporary, coming-of-age YA fiction. It’s from a boy’s POV and mostly takes place during the summer before going into high school. I think the main character has been chubby his whole life, but spends the summer working really hard doing landscaping with his friend, and by the end of the book he’s surprised that he’s way taller, stronger, and not chubby anymore. He’s had a major crush on this hot, thin girl and ignores her chubby friend (who he DOES notice has beautiful brown eyes). I think that he and his friend spend the summer trying to surprise the hot girl when she’s sunbathing so that she’ll sit up without her top on. I think that something crazy happens at the end of the book (like an escaped dog, or someone being chased through the yard), and she DOES sit up but the main character misses seeing it? But his friend does and is gobsmacked lol. Anyways, the chubby girl by the end of the summer ALSO gets thinner while she’s away at camp and is suddenly all sexy in a new swimsuit. The main character doesn’t recognize her at first, but then recognizes her beautiful brown eyes. He kisses her and they start the new school year.
Lost Classics of Teen Lit: Name That Book! 
Pretty sure this is “The Biggest Klutz in Fifth Grade” by Bill Wallace.
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IT IS! As soon as I read “Fat Pat Berry the Twinkletoes Fairy” in the Goodreads description, bells went off! Side note: I cannot believe that the characters were in 5th grade.
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One Fat Summer by Robert Lipsyte?
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I thought it was”One Fat Summer” too! And the girl was not overweight but she had, according to the story, an incredibly large nose. Over the summer, he loses weight doing his job and she has rhinoplasty. At the end of the summer, the two besties (“Two things we never talk about: my fat and her nose”) meet up on the beach and despite the fact that they are both now being pursued by multiple others, realize they have been exactly right for one another all along.
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