Is it possible to survive a day spending 1000 yen only for food?

Depends on the circumstances, are we talking about a standard 3 meals a day? If so then no. You could probably afford enough for just one meal, with a small bit of change left over but that would be it.

Edit: When I meant meals I had meant full, balanced meals. You could possibly get 2 dinner packs from a convenience store (which are cold) for about 1000 yen

If I can live with 2000 yen a week, you can survive with 1000 yen a day. Just go to your nearest 100yen store and pick out 9-10 food items. That should last you at least a day, maybe 2 if you buy in bulk (As in those big liters of water, an entire loaf of bread, etc) and plan out your meals accordingly. Here's a sample meal plan:

1) Breakfast: A piece of bread (Or multiple slices of white bread) and something to drink (210 yen)
2) Lunch: A pack of instant noodles and 1-2 rice balls (315 yen)
3) Dinner: A pack of white rice w/ pack of curry, a fruit of your choice, and something to drink (420 yen)

And you still have 55 yen left over

Thats alot of carbs!

While im aware that 'times can get tough' in some countries in regards money, wages etc. I think at least having solid and somewhat balanced meals would be important. Down the line if you don't you may run into other problems and might have to visit the doctor (which will cost you even more money in the long run).

You could have decent solid meals on a limited budget. But you would have to be willing to:
- Cook for yourself
- Shop around for places that have decent prices/deals
- Look out for special offers. As far as im aware, supermarkets do 25-50% off deals for items late in the evening. Which would be a better time to shop.

Carbs won't be an issue because I can guarantee that he'll lose a good 10 pounds by the end of the first month. If he's only doing this for a short term (1-3 months), then it's perfectly fine. The meals won't be half bad, he'll still have enough to eat a solid meal from time to time, it'll save him tons of money, and it's a guaranteed way to lose weight.

I do agree that it's pretty bad long term (Over 5 months) and will have a negative impact on your health. But if this is your only option, then I suggest you take lots of vitamin supplements on a daily basis and find a way to borrow more money.

Ok thx guys, you help me alot :] I heard snakes are tasty ^^