Will eating lots of nuts make me put on weight?

Nuts do have a lot of fat in them, but they reduce you're appetite so you eat less, and they increase metabolism. And studies show that they cause little to no fattening (mainly the raw, unsalted ones). They have loads of health benifits, so go mad!

I spent about 2 or 3 days eating almost nothing but peanuts, and I got so constipated I was ready to die, as in casket. Thank God for milk of magnesia. It knocked the **** out of me. The first time was a huge relief, but the next three helped too. After that I kept going and going for almost a day. It was a minor inconvenience compared to being all stopped up.

Nuts are healthy but as you said they're high in calorie and protein. At least make sure they're not salted (natural). If you're afraid of overeating take two handfuls or less in a cup instead of eating them from the bag itself.