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Comment by dfjkdksjds789 | Hacker News Reader

Super useful outcome, especially given I find that people think that after reaching even young ages 24, 25 even begin thinking that metabolism has some extreme drop off right after reaching young adulthood

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It’s an inevitable outcome of a culture so focused on age. I watch twitch streamers in their 20’s talking about how they’re old already. Narcissism isn’t just a social phenomenon spread online, I think it actively contributes to many public health concerns we’re seeing today.

I agree with your observation, but at the same time, I do think that what a lot of these people might be expressing is their observation of the disconnect between their socially implanted expectations (you're an adult when your 18/21! you are now -mature-), and their experience reality. Which is that for many (most?) people who go through the typical North American education pipeline through university/college (and I'm only making this limitation because that's my experience, and the experience of most of my friends), that looking back, they were definitely not "mature" at 18/21. They probably weren't even mature when they graduated undergrad or started their first full time job out of school.

Everyone has a different point, but they typically recognize somewhere in their 20s that 'oh wow, we keep changing and maturing'. And the first, most basic way to express this observation is with a pretty crude 'oh wow I'm old'. I think eventually, most people can move beyond that first reflexive observation.

I some times make the following observation:

When I was 15, I thought I had grown up quite a lot and looked back on my 10-year old self as someone who was just getting started.

When I was 20, I thought I had grown up quite a lot and looked back on my 15-year old self as someone who was just getting started.

When I was 25, I thought I had grown up quite a lot and looked back on my 20-year old self as someone who was just getting started.

When I was 30, I thought I had grown up quite a lot and looked back on my 25-year old self as someone who was just getting started.

Now that I'm 37, I think I have finally grown up and my 30-year old self was just getting started. But I recognize that my 42-year old self will probably look back on me and still see the same pattern.

6 years ago I was an idiot.

6 months ago I was an idiot.

Last week I was an idiot.

...

Glad I'm smarter now.

So the results show that on average, metabolism is stable from 20 years onward. That means that there actually is a drop from 18 to 25 (it's there for men at least when you look at Fig 2). Now think about where most people will be anchoring their perception of "adult" from (it's going to be some value in that range). That means that there will absolutely be plenty of people who experience a real decline in metabolism in the years following their "personal adult threshold".

Now, that's a pretty small drop, so definitely the other life transition (probably starting an office job, living alone) will probably play an even larger part to any weight related changes. But even given a hypothetical case where someone kept the exact same activity level, the amount of metabolism decline over that period is probably small enough to delay the onset of any noticeable body composition change (like order of 10 pounds) for a few years, adding to the mid to late 20s experience.

Such rumors are created and spread by people who want an excuse rather than a solution. This wont help them since they want to cling to their excuses, but it can help others ignore those rumors.

I found the misconception useful because it prompted me to invest time in improving my diet in my 20s, before it was too late. Even if my metabolism has stayed the same since then, the no-vegetables-or-fruits approach would have caught up with me at the same time "low metabolism" would.

Anecdata: I ate 3500-4000 calories a day of mostly junk in high school and college. I lifted weights some. I (barely) “had a six-pack”. No sports, only incidental cardio.

Around age 21 or so, I decided to try to drop a couple pounds and make it a really cut six-pack. I ate a strict 1400 calorie diet (packaged food to make it easy, no cheating at all) for about three months. I started running a couple times a week. I’d reckoned this would only take a month or so. Found the calorie deficit pretty easy, actually. Three months in, the scale showed one pound of loss.

Discouraged, I returned to my old eating habits.

I immediately gained about 15lb. Had to drop soda completely to stabilize it (i didn’t drink much alcohol then). Slowly got worse through my 20s. By 30, not turning into a blimp required a careful diet. No more 4k+ calories of pizza, soda, and potato chips without (visible) consequence.

My metabolism 100% for-sure changed in my 20s, a ton, not gradually. But I may have killed it, and perhaps I would have been able to keep doing what I was doing another couple decades otherwise (I would bet zero dollars on it, but hey, I guess the science disagrees, I just find it literally incredible)

Teens are growing until early 20s that’s why they can and do eat so much. When you stop growing you enter into your adult metabolism.

I started gaining weight/fat in my mid 20s and had to adjust my eating habits from what was normal in the preceding 8-10 years

Sure, hgh+T is a hell of a combo, but TFA claims a gradual change from teen metabolism in one’s 20s. I experienced a switch-flip that cut north of a thousand calories of apparent metabolism in a matter of months.

but the article says it's gradual. gaining 20+ lbs in a year not gradual.

same here but at a later age

this seems to agree with a lot of people's personal accounts. A switch is flipped in which the body for whatever reasons starts hording energy. maybe it is stress from family life or work related... who knows...The weight comes on so fast... it's nuts how much weight some people gain starting at 25 or so. Guys who were 130-180 lbs lean in college now 240+ lbs all a sudden at 30+.

I don't buy your anecdote.

Those are the figures people always estimate. Always the same story: 4000 calories when they were skinny, and now they can't lose weight on 1500 calories when their maintenance intake is 2600.

Then you make them log their food for a week and they are eating 3000 calories when they swore they ate no more than 2000. In my 20s I worked at a personal trainer in a gym that made people log their food and 100% of people said the same thing you just did.

If you couldn't lose weight on 1400 calories then where exactly was the energy coming from? Cue the "starvation mode" meme where people claim their body becomes so efficient that it only needs 1400 calories to maintain their 270lb body.

> 4000 calories when they were skinny, and now they can't lose weight on 1500 calories when their maintenance intake is 2600.

4000 is a conservative estimate. Four pop tarts, an entire large pizza (all you can eat buffets FTW), two liters of soda, and an entire large bag of chips was, like… a totally normal day for me. There’s probably also be some cookies or hostess donuts in there, too.

> If you couldn't lose weight on 1400 calories then where exactly was the energy coming from?

No clue, but I didn’t cheat once and ate fixed meals of pre-measured calories every day. So.

According to the paper this is "Fat-free mass-adjusted expenditure", and testosterone DOES start to slowly decline after around age 25. The trouble people have with starting to gain weight easier as they enter their 30s and 40s is caused by this since they'll lose muscle mass as such hormones decline, which causes fat gain assuming similar food intake and activity levels, this effect is not included by adjusting for fat-free mass.

I also think 30-40 is more likely caused by life just being more complicated! Juggling kids is basically a full time job, and many families are two income families. Hard to hit the gym when your child, who cannot be left alone, increases your effective work hours to 80-90/week minimum no vacation no breaks.

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