What causes obesity? A major new study is upending common wisdom

16 pointsposted 7 months ago
by elsewhen
(msn.com)

23 Comments

jbreckmckye

7 months ago

Summary (no gpt):

- Why are people in the West fat when people in developing nations are thin?

- Prevailing wisdom is that Westerners use fewer calories / have sedentary lifestyle

- Study compared calorie expenditures across societies and found this was false

- Cause is probably diet, maybe ultra processed foods, but not movement

- Data covered 4213 men and women across 34 countries

abracadaniel

7 months ago

The constrained total energy expenditure model is fascinating and counterintuitive. It seems the body adjusts its energy spending to keep it at steady state regardless of exercise. But, since exercise is still beneficial, it seems that too much energy spent on the “nice to have” processes are likely a source of the various diseases of sedentary life. It seems like the benefits of fasting are explained by this.

reverendsteveii

7 months ago

People who exercise have known this for years. The accepted wisdom in the gym has always been that you can't out-train a bad diet, and we've known for a really long time that outside extremes like marathon runners and swimmers the amount of calories burned by exercise is minimal and given the average American diet's relatively high total calorie count may slow down the rate of weight gain but won't stop it or cause weight loss. Between that and the way the body will adapt over time to continuous strenuous physical activity to become more efficient frankly idk how it became "common wisdom" that obesity is caused by a lack of activity. I think it might be less to do with the facts and more to do with the personal, individualist orientation of our loci of control. To do something about processed, calorie-dense but nutrition-poor foods and the absolutely bizonkerwonks portions we serve people would require slow, difficult collective action that will be resisted by a lot of people who have a lot to gain from the current arrangement of things. Saying "you personally are the problem and you personally are the only one who can do anything about it" empowers the individual over the short term and for relatively modest goals but sacrifices our ability to achieve anything that requires cooperation.

SirMaster

7 months ago

>the amount of calories burned by exercise is minimal

What evidence is there for this? All the things that calculate approximate calories burned for various exercises tell me that it's not minimal.

I burn about an average of an extra 500 calories a day doing exercise type activities. Playing pickleball, cycling, jogging, etc.

Losing 1 pound is about 3500 calories, so 500 calories a day burned is about 1 pound a week which is not insignificant or minimal in my opinion at least.

I kept my diet the same, and added about 500 cal average of exercise per day and have been seeing my weight dropping by a few pounds a month.

Obviously diet is the biggest factor, but if you just eat less and sit around all day, you body will adapt to the lower calorie intake and slow your metabolism down too and you will have to eat so little that you will never feel full or satisfied (so you will probably not be able to keep that up for long) and you will feel like crap and have no energy if you don't combine with exercise, at least in my experience.

Kirby64

7 months ago

> What evidence is there for this? All the things that calculate approximate calories burned for various exercises tell me that it's not minimal.

Minimal meaning that the amount of exercise you need to do to burn substantial amounts of calories is quite high. Your example of 500cal would be something like an hour of moderate intensity jogging, which would be a lot of exercise for someone to do every single day.

Meanwhile, eating 500cal takes like... 5 minutes? Less?

> Obviously diet is the biggest factor, but if you just eat less and sit around all day, you body will adapt to the lower calorie intake and slow your metabolism down too and you will have to eat so little that you will never feel full or satisfied (so you will probably not be able to keep that up for long) and you will feel like crap and have no energy if you don't combine with exercise, at least in my experience.

Metabolic adaption is largely overblown. You definitely will burn less calories as you lose weight, but that would happen exercise or not. The only difference there is that exercise tends to build muscle, which would burn more calories and offset some of that loss. The fact of the matter is, if you end up losing substantial amounts of weight, you will need to eat fewer calories to maintain that same lower weight forever.

In my experience, if you're losing weight then you are often going to feel not full. It's just a natural human reaction to caloric deficit. There's tricks to making it not be as impactful (e.g., eat more whole foods, less junk, etc) or medication to make it less of a problem (i.e., GLPs), but expecting to be able to lose weight and always feel full just by adding exercise is wishful thinking.

SirMaster

7 months ago

>which would be a lot of exercise for someone to do every single day.

Well I already disagree here at this point I guess. For me that is like the minimum on average. When I'm playing pickleball I'm plying like 3 hours, if i'm cycling I'm cycling like 2 hours, and if i'm jogging i'm jogging like an hour.

Humans are built to be active, not sitting in an office all day, and for a healthily lifestyle I don't think this asking too much IMO to do an hour of moderate exercise a day on average.

I kind of feel like crap when I am not exercising and feel like I have a lot more energy when I do exercise nearly every day. That's my experience with it at least.

Kirby64

7 months ago

For someone that is doing little to no exercise every day, asking someone to do an hour of moderate intensity jogging or possibly multiple hours of lower intensity activity (e.g., pickleball) is asking a lot.

Advocating for folks to exercise is a worthy cause, but you're setting people up for failure by advocating for adding a minimum of 7 additional hours a week to their schedule.

EDIT addition: Realistically, adding something like 30 mins of exercise a few times a week (3-4) is more achievable. And in that regard, it doesn't really burn meaningful calories. Maybe an additional 500-1000 a week if you're actually pushing yourself, but beginners often don't.

SirMaster

7 months ago

Well of course you don't just jump from 0 to that much a day/week. It would and should take a newcomer a few months to ramp up to that level, but I believe that most people can support that amount of activity.

I mean sure I agree that 500-1000 cal a week in exercise would be minimal which is precisely why I think people should have a more ambitious goal to work into their life even if it takes months to get to that level.

Kirby64

7 months ago

Can vs. want to. You're suggesting people get a new hobby, essentially. Not everyone wants to do that much exercise. Also, like I said, if your diet isn't fixed then no amount of exercise is going to overcome that. You'll just eat more to compensate.

ezoe

7 months ago

Unfortunately, human body doesn't work like a mechanical engine which input fuel and output work.

If you increase your calories consumption by exercise, our body reduce the calories consumption of non-vital activities to keep the calorie consumption budget.

Unless you're running ultra marathon every day, you can't increase calorie consumption that much.

SirMaster

7 months ago

Then why do I feel more energetic and alert during downtime when I am in general exercising regularly compared to when I am not? Also my resting heart rate is a little higher when I am exercising a lot. Also my muscles are rebuilding themselves between all my lifting exercises. All of this must be increasing my resting calorie burn rate I would think.

reverendsteveii

7 months ago

>Then why do I feel more energetic and alert during downtime when I am in general exercising regularly compared to when I am not?

Because feeling tired is a very complex interplay of emotional, hormonal and environmental signals and not simply a lack of fuel.

>Also my resting heart rate is a little higher when I am exercising a lot.

Weird, almost everyone else's goes down as the heart becomes stronger and more efficient during strenuous exercise, then that more efficient muscle is doing the same job the older, less efficient one did

>Also my muscles are rebuilding themselves between all my lifting exercises. All of this must be increasing my resting calorie burn rate I would think.

This part is true, and it's why serious bodybuilders trying to get as large as possible run a bulk/cut cycle. First they eat an excess of calories while working out very intensely, causing them to gain a lot of both muscle and fat, then they eat at a calorie deficit while keeping up as much of the intensity as possible. The calorie deficit leads to weight loss but the continued usage of the muscles causes the body to still try to prioritize maintaining their bulk. The way it was explained to me was "pack it on, then shrinkwrap it". This is also why serious bodybuilders take their sleep very seriously as well, as that's the part where your body actually does the repairing, rebuilding and increasing the mass of muscles that were damaged through strenuous use.

SirMaster

7 months ago

>Weird, almost everyone else's goes down as the heart becomes stronger and more efficient during strenuous exercise, then that more efficient muscle is doing the same job the older, less efficient one did

When I was sedentary for years my resting heart rate was 52, now that I am exercising an hour a day or more on average it's more around 60 or slightly higher even after I am sitting or laying at rest for a few hours, and even on full rest days.

ChatGPT seems to think that there are some possible reasons it could be:

1. You May Be Observing Temporary Increases Due to Training Load (Acute Stress Response) When you increase your activity levels—especially if the exercise is intense or you're doing it consistently every day—your sympathetic nervous system (fight or flight) activity may remain elevated for longer periods. This leads to a temporary increase in resting heart rate, particularly on days following hard workouts.

Why this happens: Exercise is a stressor, and though it’s beneficial, it still requires recovery.

Your body might be in a state of acute fatigue or incomplete recovery, especially if you're training hard and not taking enough rest days.

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2. Your Baseline “Sedentary” Heart Rate Might Have Been Artificially Low You mentioned a resting heart rate of 52 bpm while sedentary, which is low—borderline bradycardic, in fact (clinically, under 60 bpm is considered low, though not necessarily dangerous, especially for athletes).

Here’s a key insight: low doesn’t always mean "better." When sedentary individuals have low resting heart rates, it's often due to:

Low overall metabolic demand (not much physical exertion).

Potential autonomic imbalance, where the parasympathetic ("rest and digest") system is more dominant simply because the body isn’t being taxed.

Genetic predisposition toward lower heart rate—some people just naturally run low.

So it's entirely possible that your previous 52 bpm was:

An artifact of a low metabolic state, not high cardiovascular fitness.

Reflective of a body in conservation mode, not necessarily an efficient, strong heart.

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3. Your Resting Heart Rate Is Reflecting a “New Normal” of Increased Baseline Activity Now that you are exercising regularly, several things happen:

Your basal metabolic rate (BMR) may increase slightly due to changes in muscle mass and hormonal shifts.

Your autonomic nervous system may stay slightly more activated throughout the day.

You may be experiencing increased cardiac output demand at rest due to new muscle tissue and more oxygen-hungry body mass.

Put simply, your resting metabolic and cardiovascular “idle” is slightly revved up compared to before, but that doesn’t necessarily mean your heart is less healthy. In fact, it may now be more responsive, more adaptable, and faster to respond to changes in demand (a good thing).

It makes me think at least that I am burning more calories at rest now than I was before.

I don't think I should be concerned. I have noticed all sorts of improvements from lower blood pressure to more energy and more alertness and a clearer mind etc.

reverendsteveii

7 months ago

How many measurements did you take over what course of time? 8 bpm can be explained by normal variance or any number of things that might slightly elevate your heart rate. Hell, last time I went for a physical they measured it 3 times while taking my blood pressure and I was able to generate a 15bpm difference between the first and last measurement just by sitting quietly and box breathing. I was also nowhere near as low as 50bpm despite being in the best shape of my life. Hell, my dad runs marathons like most people run to the store and he wasn't at 50bpm resting on his best day.

I'd also be interested to see if it flatlines, continues to increase or decreases as you maintain this program but alas I don't think imma get a longitudinal study out of a fellow workout nerd on hackernews.

edit: also for the sake of politeness let me thank you for allowing a stranger to interrogate your diet and exercise regimen on the internet. Please know that I'm not trying to call you out, the human experience is so vast that it's easy for both of our stories to be 100% true but there also has to be some sort of common element to your experience and mine

SirMaster

7 months ago

I measure it pretty often, and consistently and I make sure to at the same times of the day and under the same conditions.

I take my blood pressure often and that machine also measures it. That's actually how I first noticed it. For years my resting rate was always 52 like clockwork if I was like fully at rest for awhile and took a measurement.

Now it's never lower than 60 and usually around the mid 60s.

So I don't know. I went from it always being like 52-54 at rest, to I can't ever get a reading below 60 anymore, so I am pretty sure something has changed. The only thing I changed was going from an extremely sedentary lifestyle to a pretty highly active one. It's been a little over a year though since changing my activity lifestyle and noticing this change, and it hasn't seemed to change or go back down yet.

I continue to take readings and use my same BP cuff so I should notice when I start getting readings into the 50s and low 50s again if I ever do.

I mean I am not sure why it was ever so low before, when I was in pretty bad cardiovascular shape, but no doctor ever gave it any concern.

The best I could find about how my heart behaved was something i've seen some call "aerobic deficiency syndrome". Yes my resting rate was low, but with even fairly light activity, my heart rate would skyrocket up fairly high and stay at that level while I maintained the activity. Like there was a big disconnect between how some people can use the test of whether they can easily hold a conversation to estimate their HR target level, but mine was way off that. I could easily hold a conversation yet my HR was 140+

I am 37 years old, and so Zone 1 or Zone 2 (where it's said you can comfortably hold a conversation) is around 92-110 (1) or 110-128 (2) bpm, but I could easily breathe and talk at 140+, so I knew something was up.

Now after this year+ of consistent activity, my HR does not skyrocket up like this anymore under these light loads, and also comes down much faster.

BizarroLand

7 months ago

Calories in Calories out, but that is only accurately calculable if you have an accurate idea of how many calories you are sending out, and if you are obese or formerly obese, the online calculators are likely not accurate for you at all.

One thing that is overlooked is that losing weight can permanently or at least semi-permanently decrease BMR, your Basal Metabolic Rate.

Your BMR is the calories you burn just to be alive, and is the foundation of almost every calorie counting system in the world.

At my worst, as a 33 year old 250lb 6'1" man, my BMR was at 1,836 Calories/day when it should have been at 2,133 Calories/day as diagnosed by a dexa scan and calorimetry test.

A 300 calorie a day decrease in my BMR from losing 100 lbs meant that I have to either find a way to increase my total metabolic burn or I have to permanently cut almost an entire meal from my diet for the rest of my life.

This was helpful and harmful in a way. It explained why when I was eating 500 calories a day under what my calculator said I should be eating I was barely losing a pound or two a month instead of a pound a week like I should have.

I was also tired and hungry all of the time, no energy, irritable and unhappy because so much weight loss had changed the way I function.

But when I quit the diet, I put on weight like crazy. I put on like 20 lbs in a couple of weeks and I didn't eat that much more than usual.

I've been checked for thyroid issues and diabetes, fortunately clear there, just a literally slowed metabolism as a consequence of losing 100 lbs.

There are things I can do to speed it back up, like going to the gym and putting on as much muscle as possible, but that also takes time and effort and work and it requires overeating and gaining weight at the same time.

Basically, once you're on a diet, you're always on a diet for the rest of your life, and the more weight you lose, the harder it becomes to lose weight if your metabolism is altered by your diet in the process.

If you're having trouble losing weight, get a Dexa scan and calorimetry test. That will identify where the fat is in your body and how many calories your body burns just sitting there doing nothing.

Once you have that data you can more accurately plan your diet to stay close to the 500 calorie/day limit to healthily lose weight. Just make sure you get re-scanned every 20 lbs or 6 months, it's not that expensive and gives you good information.

reverendsteveii

7 months ago

I've been on that journey. When I decided to lose weight I started by just tracking and I was at about 3200 calories daily. The trackers aren't perfect, of course, but given my height, weight and (nonexistent) activity level my maintenance calories hovered around 2500. Now it's down to 2200, 50 pounds later after two years of hard cutting and recomp (1800 cals/day).

>Basically, once you're on a diet, you're always on a diet for the rest of your life

If your diet is maintenance? Yeah, sorta. People get this idea that they'll get getting fit out of the way and then it's done and they stay fit forever and can go right back to the lifestyle that gave them a body other than what they want. Fit has to be what you do, esp because we live in a society where more is more and the average person is wildly overconsuming from a raw calorie perspective. That's why I hate weight loss as a goal even though that's precisely the goal that started me into the fitness lifestyle. People think that you set the goal, hit the goal, and then you're done forever and that's just not a mindset that will bring success in this.

>There are things I can do to speed it back up, like going to the gym and putting on as much muscle as possible, but that also takes time and effort and work and it requires overeating and gaining weight at the same time.

First off, cardio will do more for you boosting your base metabolism than lifting and it doesn't cause weight gain. It not only boosts your base metabolism but it burns calories immediately.

Second, I think you're a bit too focused on weight as the metric. This is a Goodhart's law problem ('when a metric becomes a target it ceases to be a good metric') and one that I had to overcome. For the first six months or so I was eating very little, working out twice/day (20 minutes resistance in the AM, then 20 minutes on the exercise bike in the early afternoon), and I wasn't losing weight. It sucked. Until I tried on a pair of pants that hadn't fit in years and they slid right on no problem. Turns out that I had naively discovered what the bodybuilding community calls a recomposition or "recomp". That's when you maintain a calorie deficit but still train to gain muscle. You won't lose weight as a number on a scale as quickly, and muscle growth is noticeably slower when you're in a calorie deficit (though not non-existent as long as you sleep well and get your protein), but your shape changes. Fat gets replaced by muscle. I also figured out that I wasn't winded when I went up a flight of stairs anymore and was even able to finish my first 5k having not really lost any weight. I did eventually drop from 210 to about 160 at 5'6" which is more than modest but less than a miracle, but honestly I reached a point in the 170s where I stopped caring about my weight and started caring about my abilities instead.

> my BMR was at 1,836 Calories/day....I was eating 500 calories a day under what my calculator said I should be eating

Holy shit dude 1300 cal/day is absurd. I'm 40, 5'6" and was 210 when I started and 1800 cal/day was a hard cut for me. 20%ish, right near what they say is the max you can maintain long-term. Even losing almost a quarter of my body weight now my daily only dropped to 1700. I'm not here to tell you about your life but those numbers just don't jive with my experience at all. You're bigger than me and younger, it would be an outlier if your BMR was less than mine all other things being equal like level of exercise

FWIW given the data you posted and assuming no exercise the mayo clinic puts your BMR at 2350, which means a hard cut would come in between 1800 and 1900 cals/day. Idk precisely how they define "somewhat active" but if you meet that measure it increases to 2500 and 2000 for a hard cut. Can I ask how you arrived at the figure of 1800 cal/day for your BMR given that the tests you had done set it at 2100?

BizarroLand

7 months ago

The 1836 being my BMR was discovered by going to a dexafit clinic and getting a BMR calorimetry scan. I had assumed based on weight and age that my bmr was 2100ish, so I was setting my daily calories at 1600 + whatever I burned through exercise.

When that all comes out in the wash, that meant that I was only burning 200ish calories a day, so it would take almost 3 weeks to lose a pound.

jbreckmckye

7 months ago

When I trained for a half marathon, I didn't lose any weight. I just became very hungry.

(And, unfortunately, when I injured myself, I kept being hungry - and gained mass)

reverendsteveii

7 months ago

I spent a year powerlifting and lost absolutely no weight, then spent 2 years powerlifting while restricting myself to 1800 cals/day and lost weight. If we're doing personal anecdotes.

If we're doing hard data, I think you're overestimating the impact of taking 500 calories a day off of the average American's diet, which comes in at around 3800 calories/day (https://www.ers.usda.gov/data-products/chart-gallery/chart-d...). Assuming 3300 net calories per day after exercise, one would have to be in the neighborhood of 400 pounds for that to be below maintenance level assuming 40 y/o moderately active based on the mayo clinic calorie counter (https://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-...). Hell, I ride a bike 6 miles and lift weights every day, have done for two years, and my maintenance calories are still only in the 2200-2300 range, which means if my diet was average I'd be exercising every day and still putting on pounds rather quickly. Tldr - I think your results are an outlier because you've underestimated how much better your existing diet is than the average.

SirMaster

7 months ago

It shouldn't matter what the diet is. 500 cal a day is 500 cal a day and that adds up for most people on average to 1 pound a week. Whether it's 1 pound a week that you are now not gaining or 1 pound a week that you are now losing, or something in between, it's still ~1 pound of body comp worth of calories which IMO is not "minimal".

I never said exercising 500 calories a day means you will lose weight, I just disagree that: "the amount of calories burned by exercise is minimal" I still don't think it's minimal.

If you burn an extra 500 cal a day on average that will be about 50 pounds a year of "difference", whether that's you gaining less weight or losing weight that's all up to your total calorie intake of course.