I would guess that it woulddepends on the local economy. If a loaf of bread is worth $1 of a local fiat currency, and the local exchange rate for BTC is about $1=0.000015BTC, then I'd guess that you might be able to get about 3-5 days if you're frugal. It also depends on the buying power of your local fiat. For example, USD will get you more BTC per dollar than the Philippino Peso.