Just Bento

There are man sized bentos which are around 900 ml. Or you can use container that suits your needs, I usually go for this option if I am packing soup or salad (400-500 ml of either is just not enough for me).

haha i just saw an ad on the main page for "manly bento boxes" which i thought sounded kind of funny...but thanks i'll definitely have to check those out

All the sites that sell bento boxes sell ones with bigger capacities. I know that Bento&Co classify their bento boxes by size and I know there's one bento that's at least 1L!

I have some large boxes, not necessarily bento boxes, just plastic ones that have lids that clip shut, to use for things like salads and packing multiple onigiri for a trip. The large size Sigg box pictured here is great for this. (Though I don't recommend packing it as a regular bento, with rice and so on. I tried that once for a bento-for-two on a long trip from the south of France to London via train, thinking it may do us for two meals...and a good third or more was still left over!)

I have a three tier metal tiffin from to-go ware (http://www.to-goware.com/store/cart.php?m=product_detail&p=51). It has plenty of room for food ... one container for a full-size sandwich, one for a large salad, and one for 2+ pieces of chopped up fruit. Everything clips together for easy travel. If you packed this thing with more dense foods like pasta,rice, or meat dishes, I can't imagine you wouldn't have enough room for even a huge appetite.

While the "manly bento boxes" may be the way to go with your big appetite, you mght also look at the kind of food you are packing into your bento box. My husband has both an 800 ml and 900 ml box and sometimes he can't finish the contents at one sitting; and other times I have to supplement the main box with a small snack box. A green, leafy salad might leave you a little unsatisfied, but a salad with a variety of fiber-dense vegetables, legumes, and a protein might be just right. And don't forget to pack a small, sweet treat (a chocolate mint, a perfect little clementine, or one crunchy cookie) to finish the meal. "Small" and "treat" are the operative words here.

I got a lovely 800ml bento from Casa Bento - I'm 5"11 and fairly active, and while I want to lose weight the little 500ml boxes aren't enough food for a tall woman like me!
My husband is also pretty active & doesn't like the 'faff' of a bento box, so he has a lock & lock tupperware inside a lunchbox coolbag. His bento goes in the tupperware and everything else fits into the bag, so no hassle.
I do agree with the others about calorie dense foods though - it really does depend on what and how you pack up!

The Gel-Cool Earth 2 tier boxes are 1L together. (each tier is 500ml).