Interesting question. I think what you're looking for would want to have a neutral pH, minimum calories, low fat, salt and sugar... What you're after is a glass of water. But drinking too much water CAN have adverse effects (including death in extreme cases). Another risk is that you fill up on just one food and miss out on essential vitamins and minerals.
I reckon celery dipped in a very mild salsa wouldn't have too much of an effect in large amounts, depending on the salsa. I'm guessing you wouldn't want much onion, garlic, chili, lime, sugar or anything actually good in the salsa:
Chopped bell pepper
A little water
All mixed together in a bowl
If you're feeling hardcore you could add a little:
Chopped red/spring onion (avoiding the outer layers of the red onion and the bulb of the spring onion)
Chopped mild chillies
A TINY bit of lime juice (WARNING: LIME JUICE IS ACIDIC AND EXCESSIVE USE CAN LEAD TO CALCIUM DEFICIENCY AND GOUT)
A TINY bit of salt (WARNING: SALT RAISES BLOOD PRESSURE LEADING TO HEART ATTACK, STROKES AND KIDNEY DISEASE)
There's quite a lot of fibre in massive amounts of that though, which in excess can lead to constipation. Read these before you eat your bodyweight in celery:
Finally, a consumption management trick I heard from a coffee-addicted friend who was watching her sugar intake: Every time she put a teaspoon of sugar in her coffee, she'd also put a teaspoon of sugar in a jar. That way she could see how much she had used over the days and weeks.
If you're adding something like oil, salt or sugar to something that you're eating constantly then you might want to monitor your consumption that way. Apparently, after a week of that, my friend was shocked into halving the sweetness and frequency of her coffee.
Well, that depends on if you want to try a pico de gallo or a cooked version.
I'd go with the pico for a beginner, because you can always graduate to a cooked version later.
Essentially you'll want some good quality hothouse tomatoes (as ripe as possible), a sweet onion, fresh lime if possible, cilantro if you fancy it, and your favorite chile or Mexican hot sauce (I suggest Valentino if you're going the hot sauce route).
Optionals: jarred chipotle or green chiles in addition to fresh.
The rest is dead easy: very fine dice on the tomatoes and onion with a 4:1 ratio of tomato to onion. Add in chopped cilantro, lime juice, salt and chile to taste. Optional additions: cumin, Mexican chile powder. I usually go with a dash of Mexican chile powder because why the hell not.
Let marinate, adjust salt and heat.
Eat with tortilla chips.
For cooked versions it's essentially the same as above but you can add bell peppers or pineapple or whatever when you put the ingredients to the heat.
rice is great if you're hungry and want 2000 of something
When I used to pick apples for a living, I would sometimes be too tired the night before to get a sandwich made for luch, so I'd eat all of the bird damaged or excessively small apples that would be normally thrown to the ground to fill myself. I was usually eating around 25 or more a day on days like that. Perpetual diarrhea.
The diarrhea will have been from bacteria in and on the bad apples, not from the apples themselves. Apples have fibre, so if anything, too many apples would've left you constipated.
I know you didn't say it was from the apples, I'm just saying.