[Pocha Pocha Suieibu](https://www.mangaupdates.com/series.html?id=51960) by Tooyama Ema.
Released by [Wonderland Translations](http://wonderlandtranslations.net/).
Oota Katsuyo is a 15-year-old girl just entering high school. She’s short and plump, thanks to being the daughter of a family that runs a tonkatsu shop. She’s followed her crush from middle school to the same high school, and she’s devastated when she finds out he’s not interested in chubby girls. As she’s looking for ways to lose weight, the free-spirited president of the swimming club, Itou Hatsume, and her serious and demanding vice-president, Kaji Rinko, are looking for new members to supplement their roster of two. When Katsuyo meets Kaitani Ayumi, a rail-thin girl with an appetite that matches her own, Ayumi drags her to the swimming club to join up. Will Katsuyo have problems measuring up to the demands of the swimming club, or can she make a big splash?
More info [here](http://wonderlandtranslations.net/pocha-pocha-suieibu/).