lunarsongbird - you're going to regret asking that question after you read my answer
I remember my first diet very well. It was January of 1970, I was 18, a freshman in college, and I had put on the freshman 15 - maybe 20. Anyway, I counted calories and I allowed myself 1000 a day. Someone had told me that I could lose weight doing this, so that's what I did.
I had a calorie-counting book (no internet, iphone apps, or anything else like that back then) and I had to guesstimate my calories on many things. I also had to eat almost all my meals in the school cafeteria, so I ate a lot of the same things over and over again. I distinctly remember cutting my ice cream bar in half each day, and my table mates marveled at this. They took turns taking the other half.
I was so obsessive about it that I mapped out how long I was going to stay on the diet and how much I was going to lose by then. I met my goal, and I even remember the day I STOPPED THE DIET. My first day off the diet was Saturday, April 11, 1970 and I even remembered what I had to eat - a muffuletta sandwich from the local Pasquale's Restaurant in Hattiesburg, MS.
Lest you think I'm crazy for remembering all this, there's a reason I do - Saturday, April 11, 1970 also happened to be the launch of Apollo 13. I planned to watch it while eating my first "non-diet" meal. And that was important to me because my high school classmate and at that time across-the-hall dorm mate was the younger sister of one of the astronauts. (Fred Haise) She and her roommate had gone to the launch.
I won't go into all the details of what happened beyond that date, particularly after everything went to h*** on Monday, the 13th, other than to say it was a very eventful time in my life where I found myself "up close and personal" to an historic event. I will say that my friend ended up having to use my phone to call home to find out what happened (long story) so I found out about the explosion far sooner than most of the rest of the world.
So to sum up, my first diet coincided with history!