I've been trekking in Nepal on 6 occasions in my life and only once have I experienced a stomach upset and diarrhea, which I attributed to eating an uncooked salad in a restaurant in Pokharra. Bottled water and cans of beer are widely available in Nepal. If one avoids eating uncooked food and one eats only fruit which has been peeled, one should be fine.
Lucky you. I followed all that advice, was incredibly careful with what I ate, and still got tremendously sick. Unfortunately it's very hard to control the hygiene practices of all those involved in preparing your food :-(
Did you not have any indication of what probably caused your sickness? I remember clearly the occasion when I once got sick in Nepal. I'd ordered a meal in a restaurant in Pokhara and was presented with a salad side-dish of lettuce, tomatoes and cucumbers etc, which was uncooked.
My initial reaction was that I shouldn't touch the dish. However, I was in a modern restaurant that clearly catered to the tourists, so I took a gamble on the assumption that the staff would understand that causing the tourists to get sick would not be good for business.
Within a few hours of completing my meal, I began to feel sick and soon developed a type of dysentery. The uncooked salad was the most likely culprit.
I'm not sure how easy it would be to contract a sickness due to plates and/or cutlery being rinsed in unclean water, or due to the waiter or cook not having washed his hands after visiting the toilet, or due to a fly settling on one's food.
Other precautions I take include, always checking that the bottled water I buy is properly sealed; never accepting ice that is sometimes added to a drink, because the ice may not have originated from boiled or bottled water; and always using bottled water to clean my teeth.