So as a teenager, I was carrying 5-10kg of books and walking back and forth between classes every 40 mins.
As an undergrad I was travelling across campus multiple times a day, spent hours on my feet in labs, did multiple heavy grocery shuttles and also spent a lot of time partying.
In my first job, I was still getting up 5-6 times a day for meetings and had a decent walk/cycle built into the commute. but in my first remote job, I could be sat in the same spot for 8-10 hours without moving. And because I wasn't drinking water I wouldn't need to go to the bathroom... /facepalm I'd also be so engrossed that sometimes I'd forget to turn on the lights...
So even though I do more than an hour of intense exercise a day, my activity outside of those exercise hours has cratered from when I was a teenager and was constantly running around.
As an undergrad I was travelling across campus multiple times a day, spent hours on my feet in labs, did multiple heavy grocery shuttles and also spent a lot of time partying.
In my first job, I could be sat in the same spot for 8-10 hours without moving.
A year in to my first job I had added 15kg (~30lbs ~2stone) - while consuming way less food and alcohol than my university days.
So look to your unhealthy lifestyle's accumulated effects in your body, atherosclerosis, obesity, pre-diabetes, hypertension, specific nutritional deficiencies, physiological mental health... And make a robust effort to improve your lifestyle, and you'll start to feel like you did, 10, 20 years ago.
Speaking from personal experience, I'm 50ish and after getting a health scare which triggered me into aggressive corrective action a few years back, I've overcorrected. My allergies have ameliorated back to old levels, I can drink beer again, and I can recover from a night out like I used to be able to in my 20's, I'm able to maintain a serious athletic schedule. Obviously most of the time I now eat really well, but my body's youthful tolerance to harm has been recovered.
Def noticing amongst my friends a few new allergies/intolerences manifesting as we get older
For some context am reasonably healthy and actually had to increase my sodium intake because I had over corrected on reducing salt consumption and was getting hyponatremic after training
Then we went away to University and in his mid-20s the poor guy suddenly, almost overnight, put on a ton of weight.
Therefore all their data is based only on fat-free mass, i.e. total body mass minus fat mass.
So all their conclusions are not influenced by the amount of fat vs. muscle.
So we could easily expect the average person's metabolism to increase as well, simply to support the extra body mass regardless of composition.
Balancing out the two effects can only really be determined through careful statistics, and is going to be extremely variable per-person.
https://examine.com/articles/does-metabolism-vary-between-tw...
https://www.brainfacts.org/brain-anatomy-and-function/anatom...
Does this change over time also?
My ex-gf was one of these people and would routinely tell people about how she could eat anything and not gain weight. But when I would go on a severely calorie-restricted diet I was still eating more than she did on a normal day. I don’t think she was lying about being able to eat anything, I think she just didn’t realize how little she actually ate.
In every case I guarantee they eat a normal amount of calories but feel like they eat a lot because they eat slightly more calories than normal in a single meal.
Like me eating two entrees at dinner at 16 and wowing everyone even though I skipped breakfast before school to play Runescape and had a tiny school lunch.
Their mitochondria use UCP1 [1][2] to generate more heat when producing ATP, thus wasting energy that would otherwise be converted to fat.
So to answer you question, hormones
Surely there is a correlation to the causation?
The head-bone is connected to the neck-bone etc...
You cannot study figures in isolation and expect them to yield some meaningful results while ignoring the influence of other figures upon those results.
- Kids move around a lot, and they're still growing/developing
- Teenagers move more constructively i.e. sports, and they're still growing/developing
- Adults move a bit less, and have almost stopped growing/developing
- Older adults try do keep moving, but with other life responsibilities it gets hard to put the same time in
- Older adults become less and less bothered about moving
- Even older adults have acquired illness and injuries and can't move as much
Seems quite simple and obvious no? - Maybe...
Those that don't fit the mould have some other reason that makes then more of an outlier to the norm.
If life today didn't offer as much assistance as the past, we would all be a lot more healthy - not to mention more active, you know walking and manual work etc...
Not to forget that the abundance of food (good and bad) will have a bearing on the results. Maybe the older people that can't afford as much food are the outliers - and better benchmark.
Unless you are suffering from malnutrition, or you are overeating the wrong sort of food (good and bad) then your metabolism, unless affected by biological factors should be pretty stable.
Isn't this what being in homeostasis means?
Doesn't the body adapt to effects of S.A.I.D. - Specific Adaptations to Imposed Demands.
https://cdn.vox-cdn.com/thumbor/U1RxtW9oglcck-2g2X_SrKzIA44=...
It seems that others don't fully support their findings either.
https://www.science.org/doi/10.1126/science.abe5017#eletters...
These critics don’t seem to disagree with the core claim about average metabolism across the lifespan.
"We compiled measurements of total energy expenditure (TEE) and basal metabolic rate (BMR) from human endurance events and added new data from adults running ~250 km/week for 20 weeks in a transcontinental race. For events lasting 0.5 to 250+ days, SusMS decreases curvilinearly with event duration, plateauing below 3× BMR. This relationship differs from that of shorter events (e.g., marathons). Incorporating data from overfeeding studies, we find evidence for an alimentary energy supply limit in humans of ~2.5× BMR; greater expenditure requires drawing down the body’s energy stores. Transcontinental race data suggest that humans can partially reduce TEE during long events to extend endurance."
However, after the honeymoon period the experience made him realize that not everything is explained and fixed by testosterone. He still had some mental health issues, he still had to work for gains at the gym, wasn’t suddenly full of boundless motivation. All this despite being put toward the upper end of the range for a long time.
This seems to be playing out with a lot of young people going to TRT clinics: The TRT clinics are prescription writing factories that will find an excuse to give almost anyone TRT. They make claims that the normal ranges are wrong and the only correct result is to be at the top of, or above, the reference range. They start people on insane beginning doses like 250mg/week because it gives them a rush to feel like it’s “working”, especially before their natural production shuts down.
The clinics also try to lock people into getting their prescriptions from the clinic in a subscription model. They basically get people hooked, literally dependent on testosterone because their endogenous production has shut down, and then require them to order the testosterone through their pharmacy to continue receiving the prescriptions. If they go to a family doctor, the family doctor will probably decline to continue writing such high dose prescriptions because high doses generate significant side effects, so the person returns to the TRT clinic.
It’s really bad out there. I think we’re headed for tighter regulation of these clinics soon, or at least I hope so. Every time I listen to the radio I get several ads for different clinics every hour promising men they will lose weight, be better in bed, have more energy, conquer the world.
That said, permanently messing with your hormones as a younger person for no good reason is insane and I would try to talk anyone I knew out of it.
Fun fact: I had an endocrinologist at the University of Minnesota medical clinic tell me that going on TRT wouldn’t affect my fertility. Cue IVF 8 years later…
For some it's not really convincing. They look at it like doctor perscribed steroids.
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.
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.
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)
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.
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
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+.
And still weigh much more than when younger.
Proving that its not metabolism would imply that our weight gain in later life is a combination of other factors. I would bet good money on the increase in sedentary leisure activities, the reliance on motorised vehicles and a lack of energy to be active.
I would bet on those long before anything as nebulous as diet or intake volume.
We can reverse that, like we can revere many ways we slowly decline, just need a right mindset. Spend a really active vacation or start a new sport and lack of energy of yesterday will be gone, to certain extent. One can always do some dramatic change in lifestyle to see a dramatic change in body, weight, strength, stamina etc.
I see as people get older their mental model of how they behave and think often mimics somebody much older than their actual age, acting as if they are completely powerless to greater evil forces of muscle atrophy and weight gain. It simply ain't true but going against it is certainly harder than just complain.
1. We eat out more as adults. Our skinny kid/teen selves didn't even have the money/vehicle/norm to eat out much less do it daily like we can as adults. This also includes eating out during our lunch break. Every time we eat out that's an easy 1000+ calories.
2. When you live with a partner, every time they ask "wanna eat something?" and you say "yes", that's a moment you wouldn't have eaten had you been a bachelor. We'll even say yes when we aren't hungry.
It's funny how much we want to believe in factors out of our control.
Actually the main thing that changed for me is I started compressing all my eating into 1-2 meals per day. That way I could track it. Before I couldn't tell you if "I haven't changed my diet" because it was a continuum of eating from morning till night. I have no idea what changed over time, couldn't even tell you for one week. Once I "bounded" it I was able to bring my weight down quickly.
Btw, sorry if this sounds snarky, it seemed like flagging this as anecdotal was the right way to start so I copied it.
A diet that contains a high nutritional content will prevent you from over-eating due to satiety signals (unless you have a hormone issue) rather than eating to the point of feeling "stuffed" - if someone is eating to the point of feeling "stuffed" then it would suggest that they are not eating food with a high nutritional content, or that they have some disorder that is interfering with their normal eating process.
If you look to the animal kingdom, the lion kills the zebra, feeds then walks away, the next in line feeds, then walks away, etc, etc... no animal eats until they are "stuffed" - if they did then they would become another animals prey because they are too "stuffed" to move!
No wonder some countries consider it rude to clear your plate of food. (too bad the Brits do this the other way around!) lol
if this were true it would be possible to create a diet full of foods with such satiety signals and the obesity crisis could be fixed. way easier said than done. 7-grain bread is very nutritious yet a loaf is easily 1000+ calories. Easy to overeat on it given it's just mostly air.
If you are eating 3000 calories of healthy food and you used to eat 2400 calories of junk food, why would you weigh less now?
Inactivity alone does not explain it. Consider for example Bill Gate...according to his resume, in which he lists his precise height and weight, in his 20s he weighed just 125 pounds. It's evident he has put on a lot of weight, all in his mid-section, well before he turned 60. His job literally entailed sitting at a computer all day coding. If anything, given his philanthropy efforts and retirement, he is more active now than he was in his 20s when working full-time at Microsoft. Is he eating more? I doubt it.
For so many people, celebrities for example, a switch is flipped in which there is sudden weight gain after the age of 30 or so, like John Travolta, Stevie Wonder and others. Because celebrities are photographed, you can see the weight progression and the abrupt jump in weight. Even with money for personal chefs and trainers, not gaining weight is hard.
I can personally attest that if I ate the same quantity of food now as I did at 20 I would gain weight, and no I'm not 60. And I am just as active , maybe more so. So yeah not buying this study.
So, four paragraphs all based on this assumption.
Why couldn't it be the case that a 20yo obsessive computer nerd eats less than a lavish billionaire?
I assume they don't help much when you're young, because you're already healthy as a youth.
Presumably waiting until you're on your deathbed to start high-intensity intervals is not the best idea either.
Supposing a person had a limited budget of "anti-aging firepower" in the form of pills, exercise, etc. -- what age would be most impactful to apply it?
https://peterattiamd.com/outlive/
I wouldn't think of this from a limited budget perspective. Much of what you can do is cheap or free. It doesn't cost anything to go to sleep earlier.
The first outlier I see is female health and PCOS, starting in mid 20s for women.
The next outlier I see is insulin resistance and pre and diabetes based metabolism decline.
From a hormone perspective, nose, ear, chin (femalr), and head hair seem to be going under significant change.
You go from a more active young person that eats just enough to get back to hanging with friends to binge drinking in an instant. Then you go from that to a much lazier, snackier lifestyle of 9-5.
Yeah, people on the whole do get fatter in their 30s, but that’s very easily linkable to lifestyle.
That by our early 20s our metabolism has already slowed (sugary food, alcohol, precipitous drop in activity)
I did notice a decline in metabolism/muscle mass in the past several years, so I took to walking rather than driving in the city/neighbourhood and eating more and regularly which seems to have brought my levels back up somewhat. Now I look like someone who only goes to the gym on leg days.
That we maintain a baseline temperature doesn't tell you that metabolism alone is all that regulates it, there are other factors.
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