Ned is horrified by Camp Lean-Too's strict policies, but soon finds he's not alone: Richard Napoli, Darryl "Hog" Hawkins and Max Cohen are veterans of the camp who are more than happy to help Ned through the hard times ahead. Together, the four boys find ways to cheat the system and indulge themselves without getting caught. Somehow they all manage to lose weight despite their candy bar binges and stolen cheese sandwiches from the camp kitchen.
The real trouble starts when Ned realizes he wants to lose weight the right way, but it's not going to be easy with Grandma always cooking up her delicious, fattening meals and confections. But when there's a will, there's a way.
May have been the inspiration for the 1995 film Heavyweights.
This story contain examples of:
- Ambiguously Jewish: Grandma Rose.
- Big Brother Mentor: Jamie is literally this to Ned, with his parallel storyline of trying to do better on the track team
- Big Eater: Nathaniel "Ned" Robbins in Jelly Belly starts out as this. His friends at summer diet camp — Richard, Hog and Max — are straight examples, especially Richard. And Richard's parents.
- Bratty Teenage Daughter: Elizabeth, who's always snide about Ned's weight.
- The Bully: Phil Steinkraus, who's always mocking Ned over his weight, stealing his lunch, and saddles him with the cruel nickname "Jelly Belly".
- Calling The Old Lady Out: Ned tries to avoid this when he talks to Grandma about his diet, but she doesn't listen and he ends up yelling and hurting her feelings. Luckily, he apologizes and she agrees to help him lose weight.
- Cold Turkeys Are Everywhere: Ned Robbins is on a strict diet and has to put up with his family chowing down on delicious, high-calorie foods, like spaghetti and breaded veal with blueberry pie for dessert, while he's stuck eating nothing but lean, broiled meats and vegetables. Even when he becomes more serious about losing weight and eating healthier, staying away from junk food is still an effort in and of itself.
- Comfort Food: Deconstructed. Big Eater Ned struggles with his weight throughout the book, not helped by the conflicting food messages he receives from his family. His parents tell him he needs to lose weight, but Grandma Rose continues to make him fattening meals and sweets as she truly believes food equals love.
- Determinator: Once Ned decides he truly wants to lose weight, he goes at it full throttle.
- Diet Episode: The first half of the book is this, right down to the boys getting caught sneaking candy and snacks. Subverted when Ned gets serious about losing weight and is better able to withstand temptation.
- Embarrassing Nickname: Richard's parents call him "Roly". Likewise, Phil Steinkraus tauntingly refers to Ned as "Jelly Belly".
- Fat Camp: Where half the story takes place. While it's not the sadistic kind, and protagonist Ned would actually like to be thinner, he hates the place and befriends kids who have no intention of losing weight or keeping it off if they do.
- Food Porn: The book has this in spades. Considering the story's told from the perspective of a kid who loves to eat, it's to be expected.
- Four-Temperament Ensemble: Ned is Melancholic, Richard is Choleric, Hog is Phlegmatic and Max is Sanguine.
- I Am Big Boned: Ned's grandma insists he's not fat, he's just big-boned like her. Even after Nathaniel himself tries to get her to acknowledge that he really does need to lose weight and that she could help by not cooking so much food for him. At least one of the kids at camp has parents who are the same way.
- If It Tastes Bad, It Must Be Good for You: Almost all of the food at Camp Lean-Too fits the bill, as does Ned's diet dinner shortly before he leaves for camp. Later subverted when Ned realizes how tasty and filling some healthier foods can be.
- Little Miss Badass: Ned's friend Libby, afraid of the class bully? Hell no!
- Known Only by Their Nickname: Hog is only called "Darryl" twice throughout the book. Ned himself is rarely ever called by his real name, either.
- Phoneaholic Teenager: Ned's sister Elizabeth. As one line describes it:Last year she got her own telephone, and like Jamie says, "We haven't seen her since."
- Supreme Chef: Grandma Rose, big time. Also Richard's mother.
- Through His Stomach: It's implied that Grandma and her late husband's relationship was built heavily on this trope. A non-romantic example has Ned mentioning how Elizabeth's boyfriends often ignore her in favor of Grandma's freshly baked pies or cakes.
- Trademark Favorite Food: Max Cohen's Hershey Bars, Ned's fondness for Milky Way bars.