Why did so many people I went to school with (including me) gain weight in our 20s

In My Humble Opinion
1

Let me share what this thread isn’t meant to be, and I’m hoping it isn’t going to end up as. A thread where people assume that an individual’s level of sloth and gluttony is a perfect 1:1 correlation to a person’s level of bodyfat.

What I am asking is what hormonal and biochemical changes occur in a persons 20s that cause them to gain weight. I experienced it, and many many people I went to school with experienced it. Looking at the pics of people I went to school with, tons of people gained 50+ pounds between their late teens and early 30s. Genetics didn’t change. Environment didn’t really change. Its not like fast food didn’t exist a decade ago.

I don’t personally believe it is lifestyle, because we ate shit and barely exercised when we were young either (I exercised far more in my mid 20s than I did when I was a teenager, burning on average about 4000+ calories a week in activity in my mid 20s, and was way fatter in my 20s despite the extra activity. I ate what I wanted when I wanted both in my teens and 20s). So the ‘sloth and gluttony’ argument doesn’t make sense to me.

What exactly causes this transition? Is it common for people to gain weight in their 20s and early 30s? If so, why?

2

Well the simple explanation would be that excess calories consumed when young are used in part to help build their growing body. After your body matures, then it gets added as mostly fat.

On average (yes problems with this) people gain something like a pound a year. That is like 10 calories a day.

3

That is possible. But I read somewhere that caloric intake is very well regulated by the body if the body is left alone. I don’t have the name of the paper, but it claimed that a person’s intake and usage are balanced fairly well, down to less than 1% error (meaning a person’s body when it reaches equilibrium will increase metabolism and/or lower appetite if intake goes above usage, and do the opposite if the opposite happens and intake goes below usage).

So something happens in your teens and 20s where your body decides to increase its intake and/or lower its usage to cause weight gain. In our teens we had access to unlimited food, but we didn’t gain weight despite the fact that we could eat whatever we wanted, whenever we wanted. In our 20s we did gain weight from that.

Eating an extra 100 calories a day is 10 pounds a year, 100 pounds a decade.

4

Do you play sports regularly? Real sports, not NBA Live or Madden. Ride a bike? Run? Hike? Lift weights?

Burn more calories, and eat better food. The best thing is a workout buddy. Get someone who can keep you motivated to go outside and do whatever it is you do. You know, the guy who shows up at your door and tells you you are not skipping the pickup games at the basketball court again.

Don’t beat yourself up. Your peer group is not the first to gain weight in their 20’s.

5

Do the math and you’ll find that you’re eating more and exercising less. Metabolism slows as you age, but not very much, and not all at once. “Metabolism” and “genetics” are more excuses for weight gain than reasons for it. In reality, human metabolism just does not vary that much.

Memories lie. You remember eating more and exercising less as a teen because that’s what is most convenient to your self-esteem for you to believe, but it’s probably not true.

6

Like I was saying in the OP, when I was in my mid 20s I did 4000+ calories a week of activity. Several hours of cardio, lifting weights and several hours of walking each week. When I was about 16/17 I drove everywhere, spent all day sitting in school and didn’t get as much activity.

I’m not really interested in losing weight, that isn’t why I’m asking about this. I’m wondering if anyone has figured out what biological changes occur as you age that predispose you to weight gain. A person’s testosterone levels don’t drop until they are 30+. Growth hormone levels drop after puberty, but I don’t know how rapid the decline is. I don’t think thyroid levels change. But lots of people gain weight despite lifestyle not changing much.

I’m guessing changing levels of HGH play a role, but whether that plays a major or a minor role is a total WAG on my part.

http://www.deerantlervelvet.net/wp-content/uploads/2012/08/IGF-1-Deer-Antler-Velvet.jpg

IGF-1 also starts to undergo decline around age 20, that could play a role too.

7

Not to beat a dead horse, but you did gain weight as a teen. Because you are being compared to other teens - you aren’t considered to added on weight as in getting fat, but most teens are absolutely putting on weight. I also don’t believe activity is the same - who else does 4 days of phys Ed after leaving high school. I had basically a full time job and full time school in high school - im almost positive it was the high point of my calorie burning.

8

I know in my high school I had a lot of hidden exercise I never thought about. Just passing between classes was considerable exercise (my hs was 5 stories). You remember that you had to sit in class, and forget that you spent 10 minutes of every hour rushing off somewhere while carrying 25lb weights, aka, your backpack & textbooks. Carrying that backpack for one hour a day burns about 400 calories.

9

My weight gain was a result of getting a full time job, not living on a campus where I was required to walk at least 2 miles a day (plus the exercise I got running frequently) just to get around and having kids and not reducing the amount I ate after having them (calorie burn from breastfeeding only works so long, you know).

That said, it’s a hell of a lot harder now to lose weight than it used to be, probably because of age. I was losing weight really well earlier when I cut out most carbs; then I noticed I was turning into an absolute raging lunatic, called my doc about it who recommended I knock off the low-carb dieting and I suddenly was normal again. It sucks because that means I have to put more effort into finding other ways to lose weight (like exercising and trying to think of how to fit healthy carbs in - was much easier not to think about it when I just cut out a food group, dammit).

10

This. And it college there’s even more hidden exercise, as you’re usually walking between buildings to switch classes. I know I walked about 5 miles a day in college, simply due to how far my dorm was from the main campus, and how far apart the buildings on the main campus were.

Less hidden exercise + less formal exercise (no time for organized sports, no mandatory PE at work) + cessation of growth + keeping the same eating habits = weight gain in one’s 20s.

11

Maybe more disposable income and more places to use it to buy junk food (my school meals weren’t great but we were never offered Big Gulps or stacked burgers). Also being in work is more stressful than at school, with bills and commitments, so maybe you eat to relieve stress and so each meal isn’t as satisfying and you eat past being full.

And adults move less than teens, just look at some teens and see their nervous energy and the way they’re always moving around. All the time they’re moving they’re not eating. It might just be me noticing more but I see overweight adults eating way more often than I see teens eating.

12

For me, I’d add two items to the equation:

  1. No more restrictions on WHEN I could eat - not restricted to dining hall hours for obtaining food, desk job where I could grab a bag of chips out of the vending machine whenever I wanted, no opprobrium from co-workers for snacking (unlike the frowns you’d get from profs for rustling food wrappers in class)

  2. No more financial restrictions on WHAT I could eat. I no longer had to choose between going out to dinner and going out for drinks because I could afford both. More disposable income = less cooking at home, and richer, more calorie dense food choices in general.

13

I didn’t gain it until my late 20’s, but when I was in my early 20’s I worked retail on my feet and walked around campus as a grad student. In my late 20’s I got a desk job and bought a house and boom, gained weight. I didn’t believe anybody when they said that it would happen, but it totally did - I used to be that really skinny fast metabolism girl. Didn’t weigh over a hundred pounds until I hit that point, and then I let it slowly accumulate because I wasn’t in the habit of watching what I ate or getting much exercise.

14

I was a beanpole until age 40, when I went from under 140 lbs to over 180 in about 3 years. I had to adjust my habits a bit to stay at 180. Whatever happened to everyone else in their 20’s didn’t happen to me, at least, not then.

15

I’m assuming your lifestyle didn’t change much during that period. when I and others were young we had access to virtually unlimited western food, but didn’t gain weight until later.
I’m guessing something happens to the body to increase appetite and/or slow metabolism so the set point goes up with age and engaging in the same level of activity and having unlimited access to the same foods causes a higher set point. being thin requires far more conscious effort with age. if science figures it out maybe they can figure out the opposite.
a weight gain of 40 pounds in 3 years only requires an extra 150 calories a day. but again, it doesn’t explain why it happened at 40 and not 28 or 22 or 36.

16

Anecdotally, it happens when you buy a house or have a kid.

17

In my non-expert opinion, your body does control your weight more than just calories in - exercise = weight gain. People want to reduce it to that because it is simple, but we are not 100% efficient machines.

When I was a teenager, I was a scrawny kid, so I decided wanted to gain weight. I ate and ate. I ate all kinds of high calorie foods like milkshakes on top of too much of a fairly balanced diet. I ate to my limit. I gained about 4 pounds, then I hit a wall in which my body would not gain anymore.

It was obvious that my body was just pooping out the extra calories, because they were not staying in me. It decided it did not want them and so it got rid of them.

So, in my opinion, there are other ways that calories get out of your body than just burned.

ETA: Obviously now I am older and have a house, a kid, and a desk job. I can’t do this anymore.

18

I’ll put in another vote for “you are mis-remembering.”

Teenagers burn up a lot of energy in the course of a day. Think about high school- every 45 minutes or so, you get a bell that rings that makes you get up and go someplace else. Between changing classes, meeting friends during breaks, taking lab and gym classes, and generally just hanging out, you are getting a near constant stream of low-level activity in. This slows down a bit during college, but even then you are usually walking around campus a fair amount. Physical activity may feel more significant when you go to a gym and spend a set chunk of time on it, but it’s just as present when it is blended seamlessly into your day.

To give an example, I’m a pretty heavy daily walker and my pedometer tells me I average four miles a day just getting to work and getting errands done. If I were to go to a gym and run four miles, it’d register in my mind as a pretty intense workout. But calorie-wise, my daily walking around is basically the same thing.

In terms of food, teenagers may eat crap, but they generally don’t have unlimited access to crap. You are still mostly eating out of a house stocked with food your parents bought, which probably isn’t a bounty of your favorite things. As an adult, I stock my house with my favorite snack food, and if I eat the whole bag of chips in one sitting, nobody is going to yell at me. Snacking is another factor. Most high schools put some limit on snacking in the classroom, and your schedule doesn’t leave a ton of time for bored eating. As an adult, I can snack at my desk all day, and I often do find myself taking trips to the vending machine just to eliminate the tedium of office life. You usually see this effect start in college with the “Freshman 15,” as people discover the all-you-can-eat aspect of the dining hall. It’s a completely different scene than the snack bars, cafeterias and parent’s pantries of high school.

Finally, the people you are talking about may well have been putting on extra weight in high school and college, and it just takes a while for it to start being visible. If I start out am average weight (let’s say I’m 130 lbs as a 5"6’ woman), and I’m gaining an extra pound a year. By 20, I’m 135, which probably just melts in with normal growth and doesn’t look like much. By 25, I’m up to 145, which is starting to look robust but still fairly normal. By 35, however, I’m 155, which is noticeably large.

19

Full time jobs, often stressful and sedentary
Less time for leisure activity
Settling down and getting “comfortable” with a partner
Moving to the suburbs, leading to less walking
Have babies, sleep deprivation surrounding babies leading to comfort eating
Small children, their snacks, their leftovers, their treats
More money to spend on treats

20

human bodyweight is largely regulated by unconscious drives. there are variations both between people and within a person’s own lifespan. give a person access to the same foods and say eat what you want when you want, and people will end up at all different weights. you can consciously regulate your weight within reason. a vegan triathlete will weigh less than a couch potato who eats western foods. but if you need to be a vegan triathlete at 40 to weigh what you did as a couch potato at 18 something else is going on.
again, I’m not mis remembering. there is virtually no level of walking between classes that can account for a 50 pound weight difference. the weight difference between people who walk a lot in urban areas be suburban drivers is about 4-10 pounds. a study in Australia found people who bike or walk to work gain 2 fewer pounds over 4 years. that is almost nothing and doesn’t explain people gaining 30% extra bodyweight.
there is something other than gluttony and sloth behind this. I assume biology changes during that age but I don’t know how.