When I left home for the first time, in 2011 (some of you now feel old), I realized that I could eat anything I wanted. I had a certain budget -- made some money, and received some per month. I realized that peanut butter was among the easiest forms of caloric intake I could get. A jar doesn't need to be refrigerated, you can eat it with a spoon only, tastes pretty good, and it is cheap!
So for a period of approximately 5-6 months from mid-fall to early spring 2011-2012, I ate nearly nothing but peanut butter. Essentially, I would go through a family sized jar (approximately 1 liter/5500kcal) of peanut butter every 3-5 days. This is a serious bargain, and it is livable, as you get a huge amount of fat and protein from the PB. I didn't eat breakfast (late-ish classes), and drank a lot of coffee.
I would have about a liter of coffee, and 20-30 tablespoons of peanut butter.. so somewhere hugely north of 150 grams of fat and 60-90 grams of protein from peanut butter per day. I would say I had more than 30 days that year where I ate peanut butter only + small snacks like celery, apples, carrots, etc. On off days, I would get a huge kimchi plate or stir fry at the korean place.
You could eat 10-20 tablespoons of peanut butter in one sitting depending on your size. Afterwards you will start to get sick. I would have to drink a lot of water along with the meals, since I would wait to eat until I was hungry, then eat a lot of PB all at once. I think if you have more than half a liter at a time you would vomit, but I never tried. It also wasn't tenable for me to go longer than a few days without a non-PB meal. You start to feel weird cravings after a couple days. There's not enough amino acids, minerals, etc. in PB to form a complete diet.
** a side note about diabetes: I am type 1 diabetic, so I chose peanut butter because it has a low glycemic profile. The sugars in PB and their constituents break down slowly, and the fat creates insulin resistance at a steady, predictable rate. I hate giving insulin shots, so I would have a large long-acting insulin shot 2x per day, and eat peanut butter / coffee the rest of the day. The lack of simple sugars and carbohydrates in my diet, combined with insulin resistance from fat/protein, meant that I could control the sugars with a minimal number of short-acting insulin shots. Then, I was taking 50u (0.5mL) of long acting insulin per day; now (still adult size) I'm taking 30u per day -- that is a small child's worth of long acting insulin per day to account for the peanut butter.
Throughout, I weighed about 140-150lbs, and exercised sporadically (2x or so per week, down to 1x/wk that winter). I took up smoking cigarettes because my roommates were chinese. I didn't date at all those months, drank intermittently, and did very well academically.
I had about a 60/40 split of crunchy to smooth -- I think I prefer crunchy to smooth, but both have their place. Also I love peanuts and peanut butter still!