...and calories, unfortunately. 2 cups of peanuts and you've nearly hit the recommended 2000 calories for the day. Nuts are certainly good for you, but not in "significant quantities". As they say, everything in moderation.
Consuming more calories than you're expending causes you to gain weight, and for most (but not all) people that's probably bad for you. I often supplement small meals with large amounts of nuts and it's the calories - in the form of fats, including many heart-protective fats - that I'm after.
I believe I'm better off getting those 2,000 calories from nuts than from, say, meat or refined sugar. But obviously everyone's bodies and personal health situations vary.
answer: because his money in was greater than his money out.
doesn't really explain much, does it?
specifically, calories in/out doesn't explain: satiety, insulin resistance, muscle anabolism/catabolism, or cravings.
there's much more to it then in/out. yes, thermodynamics applies. no, humans are a bit more complicated than a terrarium.
Okay, I challenge you to eat zero calories and still maintain weight.