I'm looking for manga where the main character engage in a healthy diet. It doesn't have to be a cooking manga, but if it is it'd be awesome.
I've read What Did You Eat Yesterday? and Cousin.
I don't really care what the genre is, as long as the manga isn't too silly.

Not to be rude... but what possible interest could anyone possibly have in what a character is eating... just seems so bizarre and insignificant..

You could try tough.

There's way more bizarre request then that.

Maybe this? http://www.mangaupdates.com/series.html?id=1256
I haven't read it all, but where I'm at, the main character is a big health freak and sometimes tells the reader health tips.

hmm, Lol. interesting request as everyone else has said.
I can't think of any manga with healthy diet at a main theme or focus but some sports/martial arts manga focus on that to some extent.
In Full Contact , the karate students all eat inordinate amounts of food... not necessarily extremely healthy as I remember it, but I thought that I would mention it because it was part of their training regimen. So it likely isn't unhealthy.
Sorry, I haven't read that many cooking manga. But most of the ones I have read focus on unhealthy food (bread, pasta).
Oh, I remembered a parody magical girl manga that kinda focuses on healthy eating. Its called Miracle Dieter Miyuki, maybe that's a bit closer to your request. Or maybe I completely forgot the point of the manga.
haha, And just to be contrary there's 1 Pound no Fukuin in which the character fails to keep a healthy diet...did I mention that he was a boxer?

Cooking Papa ?

Maybe Kui Tan . It's about a detective who solves cases via eating. Although it's not really about healthy eating, you could give it a try, and some cases do mention healthy vs no healthy food.

It may sound strange but check out KAJIKAWA Takurou's Nobunaga no Chef. It is set in the Sengoku period but the main character has modern knowledge on ingredients and cooking and educates people about healthy and tasty food.

If I recall correctly Hatsukoi Lunch Box by KODAKA Nao and SHIORI only consisted of healthy recipes.


________________
"Stories are what death thinks he puts an end to.
He can't understand that they end in him, but they don't end with him."
- Ursula K. Le Guin, Gifts

To be savoured:
- Blood Alone by TAKANO Masayuki
- Otoyomegatari by MORI Kaoru
- Gangsta. by Kohske
- Seishun Kouryakuhon by AKIZUKI Sorata

It's cause I usually see characters in manga chow down on junk, unhealthy food. I just wanted to see a change, if there's any where the character actually cares about their health and got a slim body. Sorry if that bored anyone.

Thanks guys for recommending me stuff, tho some of them I've already read.