Graduated 1997, female, 5"3. 115lbs to 140lbs. I could lose a little, but I was really thin in High School, and I enjoy things like the much larger bust. I think I look pretty good. 
I graduated in '99 at about 140, and I weigh about 142 now, so I’m pretty OK. I’d like to loose about 10 vanity pounds, but it’s a stable, healthy weight and I should really just get over it already :).
About 15 pounds (145 -> 160), and it’s only been four years. Most of it happened in the second semester of my junior year of college, when my refrigerator broke and I had to go back to eating in the dining hall for every meal (I wasn’t very good about resisting the donuts and ice cream). I’m back at home now, where I don’t walk as much as I did at school (there aren’t any sidewalks around here) and my sister keeps making cupcakes, so I’m kind of doomed for a while.
(Female, 5’1")
I 'm 5’7" and weighed about 130 pounds in high school. I’m just a bit under 150 right now, but I’ve been as fat as 180, so I feel pretty good about myself right now, even though I don’t have much muscle mass. I’m 50 and a male, by the way.
I think when I granulated I was 155 or so. I’ve put on about 25-35 pounds (it fluctuates a lot), and I’ll say most of it is lard.
I’ve put on about 50 pounds since I graduated from high school. Two things contributed to that: I discovered the joys of weightlifting, and I discovered the joys of a dining hall. Now I’m out of college, between gym memberships, and holding a bag of candy in my lap. I feel…great.
I weighed about 123 when I graduated in 1971. I think I’m about 124 now, but it sure looks different at almost 55 than it did at almost 18. Sigh.
Close to 200 when I graduated high school. 16 years later, 120.
Susan
Probably 30 pounds - but also about three inches in height and got hips and breasts - so 15 lbs of it is finishing puberty. (I was a young high school graduate - but could still pass for twelve when I was a senior in high school - and I wasn’t THAT young - late bloomer).
Graduated in '01, and I’m almost exactly the same. I gained about ten pounds during undergrad, then lost it the year after I graduated.
About 30-35 lbs. very gradually over 20 years, though it seemed to pick up speed after age 30. I’d like to shed 10 to 20 of them, but not enough to work terribly hard at it.
I’m 6’4". When I left school, I was a bit over 11 stone - far too thin. I really didn’t put on weight for about 10 years; since then I’ve ballooned to 17 stone, mostly flab.
I weigh 30 lbs more. This is good, as I had 16% body fat back then.
I weighed 150 when I graduated, 170 after my first semester in college, and 185 at the end of my freshman year. At the end of the following year I leveled off at 220 which has become the average in the 14 years since. After a strict diet I got down to 199 for ONE DAY before gaining weight again. I quit smoking and ballooned up to 250 in two months.
I think a lot of the weight gain in my freshman year was natural, but a large part was my diet which consisted of pizza and beer…
Twelve years later, I’m somewhere between 5 and 15 kg lighter. I’m quite amazed that I can’t pinpoint it better than that. I do know the suit I wore is too big these days, though.
I’m a guy, 5’7" and change.
I was skinny as hell when I graduated High School more than 25 years ago. I think I was around 120 lbs.
I have gained at least 30 pounds since then, if not more.
Of course I have not grown any taller.
Graduated in 1973 at about 140 pounds. Now, I weigh 160. Yeah, I’m fat - I’m 5’6" - but I’ve been fatter than this. The only good thing I can say is that I’m not as fat as my dad or my grandpa or my great-grandpa all were.
I was about 75kg (165 lbs) when I was 18 (I am guessing that USians graduate High school about then - we kiwis only graduate when we finish a degree at university).
I was still that weight-ish when I got married at 23 - my suit pants were 84cm (32 inch). 19 years later of marriage, kids, sedentary IT lifestyle and good eating, I was 113kg (250 lbs) and pushing (to be truthful, holding in) a 112 cm waist (44 inches), and I felt like crap. My wife wanted to divorce the extra 50kg that she wasn’t legally married to. So I have dieted and exercised and am now back down to 93kg (205 lbs) - she will tolerate the 30kg extra given that it is mostly firm and trim.
And I am pretty happy, but I want to lose some more. But the rest is proving harder to shift, and more exercise just seems to add muscle mass (reducing my waistline but making my legs into tree-trunks) but not changing my weight.
I doubt I can lose all the rest - I have more bulk in the shoulders and legs and am definitely fitter than I was back then (I ran 6 miles on Sunday, something my 18 y.o. self could not do, and my premarriage 23 y.o. self could just manage cycling 5km to visit my fiancee most days), and once I trim down my abdomen I’ll be chuffed.
Si
I was underweight in highschool. 5’6’’ and 115 lbs. Since then I’ve not grown any taller but I started working out. I’m up to 165 lbs. It’s a OK weight for me but I’d be happier with 155 lbs as I’ve got a little more chub around the middle than I’d like.
I’ve probably lost about 15-20 pounds since high school graduation in 1987. I was about 185 then and 165-170 now.