Miracle Dieter Miyuki

Jaoanese Title: ミラクルダイエッターMIYUKI

Plot
Yukimi, a chubby junior high student, discovers a magical dumbbell that can transform her into Miyuki, a beautiful and slender young woman in a revealing costume. But she must do battle with an evil three-star chef who tempts young girls with calorie-rich treats and dubious weight loss products, and keep her identity secret from her family and schoolmates.