I will add my voice to the quantity of available food debate by saying I had a problem getting enough especially in rural areas of Cambodia, Vietnam and Laos which were my favourite parts to visit, it was difficult to find enough and on a four month tour of SE Asia went from just over 140 pounds to 130, I am 5' 8" tall but don't let it put you off it will not kill you but you might need to take the bus sometimes.