Forage is a stupidly simple calorie journal. There's just one page, with today's food & exercise register. If you know what you're eating and just want to keep track, Forage is a lightweight utility without any fluff.

There are a lot of fancy apps with nutrition advice and barcode scanning and exercise databases. They're probably much better for most people, but this is the tool I wanted (and it doesn't take 10 taps to enter things).

Note: Forage is just a tool. Only change your diet with medical advice.