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How Your Metabolism slows down when you try to lose weight (nbcnews.com)
31 points by paulpauper on Feb 18, 2023 | hide | past | favorite | 47 comments



I'm glad to see there is more research getting publicity for things like this.

There are a lot of people out there that have never dealt with trying to lose a lot of weight who think it's all just as simple as "calories in and calories out", "it's the first law of thermodynamics, man!"

It's like saying that running a marathon is easy, just keep running and don't stop!

It is so much more complex and there are a lot of factors and more variation between people than many realize. Obesity is a true epidemic and over simplifying the problem is not helping us solve it.


CICO is good enough almost all of the time. The complications and exceptions don’t really disprove it. Most people should start there.

As someone who has lost a lot of weight and gotten very strong, and coached a significant number people in their efforts: calorie tracking works… you need to be truthful in your effort.

The micro- level issues or margins of error in CICO are irrelevant to the macro- margins required by someone who has to reduce body fat by 50 lbs, or 100 lbs, or more. If you always record something wrong, and aren’t losing the weight, you’ll still need to make an adjustment to what you’re eating to accomplish the weight loss. There’s nothing magical about 2500 calories eaten or recorded, but there is something definite about losing 5 lbs over a period of time. That’s the baseline metric. The CICO is just an adjustable control.

As an example: most people aren’t willing to cook 90% of their meals for a couple of years. Restaurants generally won’t feed you reasonable portions (or proper vegetables), which is fatal to the cause when you need to lose a significant amount of weight. Routing around those baseline truths isn’t an accurate response to the challenges. Most fit people in the gym… the ones who are there at 6am, aren’t eating out — or calorically freely —all the time either.

The problem isn’t really the science of fat loss, but the world of crappy food products and restaurant meals. Restaurants do not follow a sustenance model.


Yes, tracking calories and measuring results does work, but I have found it to be an ever moving target. The more weight I lose, the more I have to restrict and/or the harder I have to work to burn the same amount of calories. And it certainly doesn't work over smaller ranges like 5 lbs. It's pretty easy to gain or lose 5 lbs simply by retaining or losing water which seems to fluctuate a lot based on more or fewer carbs/sugar. I have to see closer to 10 lbs loss to get a good direction.

As for the micro level issues, I agree they don't really matter in the scheme of tracking everything and losing weight, but where they do come into play is comparisons. If my body burns "just" 100 calories fewer per day than someone else, that person and I can follow the exact same diet and exercise and all else being equal, I will gain 12 lbs per year while they maintain their weight.

And I have heard so many people brush off these small variations among people as insignificant. But 50 or 100 calories a day is actually very significant.


> Obesity is a true epidemic and over simplifying the problem is not helping us solve it.

A "Lapalissade". Saying an issue is more complex than its synthesis doesn't make the issue more understandable.

You won't deny we never seen any person in a labor camp or lost on a desert island coming back obese, no matter their genetics.

So yes, everyone is different and for some it is less easy than for others. But obese people should stop trying to make it sound like their body is going against the laws of thermodynamics...


While I agree, is it possible that we don't see people come back overweight because those who struggle to meaningfully metabolise their fat reserves just die first?


I have heard a story but it could well be apocryphal. This happened during the second world war. A bunch of random people from different social classes were forced to be without food for a considerable time. Some overweight aristocracts died of starvation first. Somebody probably knows the actual source.


Well if you watch enough seasons of Survivor you’ll undoubtedly see the pattern. Overweight people dominate because they clearly have their reserves of energy. Super fit gym rats tap out very early as they struggle in the physicality without their usual food/protein allotments. They simply have no fat reserves to get them through.


No obese person is claiming they are breaking the laws of thermodynamics. What they are claiming, either accurately or not, is that the rules of thumb and assumptions used to estimate their calories in and out are not giving them very accurate estimates.


Obese people just need to refrain their argument. Instead of saying “it’s a disease, genetics, etc that prevent me from losing weight even when I drastically reduce my validly count” (this is simply a losing argument) and instead argue “genetics makes it very very difficult to stop my mind from Cindy sky thinking about food and thereby reducing my caloric intake. I’m simply unable to stop eating. Genetics makes it impossible to stop.”

If they did that we could stop arguing about CICO and all this thermodynamics crap. Going against those is a losing battle. Just focus on your inability to stop eating and you’ll get way more supporters.


No, I think you need to realize that someone who is overweight could literally be eating the same or less than you and working out the same or more than you and still become overweight. That's all I'm trying to get across. You simply need to realize that biological variation is enough that some people with much stronger willpower than yourself may in fact become obese while you remain a healthy weight.


Significant biological variation is real, but very unlikely to mark the different between obese and healthy weight.

It’s an enormous divide between those two categories, and we have about a thousand behavioral contributors — mant of them social and difficult to escape —- that plainly play a bigger role than biological variation.

If you can’t manage to lose those last 20 pounds, it might be some underlying metabolism or gut difference. If it’s 59 or 100 pounds, then there’s almost certainly something else at play and an honest diet and activity survey are very likely to raise concerns.


I think anyone can do it, barring some serious medical reasons. But my point is, for some it is very easy, others not so much. I say this as someone who could drop 30 lbs easily with diet and exercise when I was younger, but now find it much more difficult.

And the variation can amount to quite a bit. All it takes is time. An excess 100 calories a day adds up to 10 excess lbs in a year. 5 years down the road and you are 50 lbs overweight.


You should be more measured, that would make your argument more acceptable. You cannot product 10kg of fat from eating 1kg of broccoli...

Moreover : so how ex-obeses who became more "average" do ? A genes therapy? And I am not referring to people who had some surgery but those who could lose tens of kgs.

From another angle : so obese people weighting 200 kg also eat like anyone else, but just have a very inefficient metabolism? NO.


Of course not. But one person could eat 10 kg of food and gain 5 lbs, while you eat 10 kg of food and gain 4 lbs all else being equal.

And yes, you can become overweight eating the same thing as someone else simply by having a more efficient metabolism. Unless you believe that there is absolutely no variation between humans, which would be ridiculous. All it takes is a 1% difference in BMR to amount to 25 excess pounds over a year's time all else being equal.


It might not be easy but it absolutely is as simple as calories in and calories out. All the other factors combined can still not override the first law of thermodynamics.


In a very basic sense it’s true. The first law of thermodynamics must be followed. But it’s a meaningless statement without explaining what people actually mean by calories in and calories out.

When people say calories in and calories out, calories in is meant to represent calories consumed as food, and calories out is meant to represent calories lost through physical efforts (exercise, and basic daily activity).

The problem, however, is that both sides of it are incomplete. There are parts of calories in that will never get absorbed by the body. If the same person consume the same amount of calories in donuts, or alternatively in lettuce, they will almost certainly gain more weight eating donuts than lettuce even if their “calories out” is the same, because a lot of the calories in the lettuce will never be absorbed by their body and will simply exit as fiber in the first place.

Then even looking at the calories out side, a lot of digestion isn’t even done by our bodies. It’s done by stuff like gut bacteria. Someone who has a healthier gut biome will likely not gain as much weight eating exactly the same foods and exercising exactly the same amount as someone who doesn’t have as healthy a gut biome.

Then there are dieting patterns. Most extreme diets, for example, drive the body to enter starvation mode and lower its BMR, so even two people doing the same amount of exercise and eating the same foods, if one of them does it in a way that makes their body think they’re starving and the other does it in a way that does not, the latter will lose more weight since their BMR will be higher.

Calories in and calories out is supposed to convey the idea that all that matters are the calories you’re eating, and the exercise you’re doing. But this is wrong because the nutritional value of the calories you’re consuming, the timing and frequency with which you’re eating, your gut health, your BMR etc are all also extremely, arguably more, important factors in weight loss.

And all of that is without even considering the impacts of certain types of foods and exercise on your mental health and satiety.

Calories in vs calories out is only accurate in the most basic and meaningless physics sense in the context of weight loss. And yet most people telling others to lose weight offer it as prescriptive advice.


> There are parts of calories in that will never get absorbed by the body. If the same person consume the same amount of calories in donuts, or alternatively in lettuce, they will almost certainly gain more weight eating donuts than lettuce even if their “calories out” is the same, because a lot of the calories in the lettuce will never be absorbed by their body and will simply exit as fiber in the first place.

That's accounted for in the "calorie in". Only the useable calories matter.


Then you misunderstand. Usable calories is your calories in if your body was 100% efficient. Some of that food will simply pass all the way through and end up in the toilet. I would suspect that skinny people who seem to not gain weight no matter what they eat probably have less efficient digestion than others.


Yes but it’s a moot point. The obese people that aren’t losing weight are not eating very low calorie diets but diets with poor nutrition. If only that were the case. They’re simply not able to reduce their caloric intake. Full stop

So whole nutrition is important it’s simply a moot point for obese people.


People are very much in control of the calories they take in. The fact that absorption and BMR varies between individuals is irrelevant. An individual can either reduce their intake and lose weight or they can indulge in hand-wringing about metabolism and gut health.


Of course, but the point is, reduce their intake by how much? And for how long? And does everyone function well long term in a calories deficit?

Like I said before, running a marathon is simple, just run and don't stop running until you finish it. So why don't more people run a marathon?


The change in BMR is terrifying because it doesn't seem to subside. 6 years after "The Biggest Loser" the contestants regained more than 2/3 of what they had lost (not even total body weight) but their RMR is still in starvation mode.


There is only calories in and calories out. Did you go a week without losing any weight? You consumed too many calories. Whether you chalk that up to "muh metabolism" or some kind of magical universe defying intervention, the end result is that you consumed to many calories to lose weight. Dial things back by 500 and see what the scale says next week.

No amount of mocking "the first law of thermodynamics, man" makes it not true. For everyone complaining about the complexity of losing weight, the gym bros just keep weighing out their chicken and broccoli to great result.


See, you are a perfect example of what I was talking about. You seem to know just enough to be very confident in what you are saying, but you are very, very wrong. Another user in an above thread lays out some of the minutia that comes into play.

Calories in: What kind of calories? When you eat them, how fast you cut them, how your body reacts to the restriction, how your gut biome reacts, how your brain and willpower reacts, how your family and friends react....

Calories out: what is your actual resting burn, how does that change as you adjust calories in, how does it change as you adjust the type of calories in, how does your resting burn react long term to weight loss....

It's as simple as calories in, calories out, just like the theory of relativity is as simple as e=mc2.


One test is worth a thousand opinions. Again, for everyone championing the theoretical complexity of theoretical weight loss, there are "dumb" gym bros, of whom I am among, who somehow defy all Complex Science™ and continuously gain and cut weight.

No amount of saying "it's complicated" makes it actually more complicated than just cutting another 500 cals from your meal plan.


Sure, you can always start cutting until you lose weight, but how much you have to cut and how difficult it will be to do so is all a part of it. I can easily drop 20 lbs in a few months by cutting. But it is not easy and as of yet, it has proven impossible to keep off as I have bounced back to my original weight 4 times over a 10 year period. As I reach that 20 lbs lost, I find my willpower begins to wane just as my metabolism starts to settle on the new caloric intake levels. Which means to continue weight loss, I will need to cut even more.

In contrast, I have a skinny brother that just doesn't "really feel hungry that often" and drinks multiple tall glasses of grape juice every day and eats ice cream every night.


Not all calories are equal. Calories from carb rich food are metabolized different than calories from “healthy“ fat rich food. Metabolism of former also raises insulin + glucose in blood stream, which influences obesity more than later.


The only way those differences really matter, as long as you are getting enough protein that you arent catabolizing muscle mass, is in what they do to how much you eat and perhaps exercise. Even if an insulin spike makes you crave junk food and not want to go for a walk, it's all still CICO to more than a first approximation.


Not to mention how different foods might affect different hormone levels and even the microbiome in your gut which seems to have a lot of affect on the brain as well as other systems.


But the body is supposed to regulate calories in and calories out automatically. You aren't supposed to know how many calories you are inputting or outputting. So pointing at this just means there is something wrong with the control loop built into the human body.


I think more likely our modern food system is causing this. We have all these calorie dense foods and methods of processing them that make them more and more delicious and calorie dense.

Take ice cream for example. It needs to be over-sweetened so that when you eat it, and the cold dulls your senses, it still tastes sweet. Most people find melted ice cream to be sickly sweet. But we have tricked our taste buds into eating a lot of it due to the cold. Same thing happens with lots of sweet foods that are offset with sour or salty flavors.


It's kindof ironic that despite it being quite simple, and there being around 100 years of freely available science explaining why it's not true, some people just can't stop saying "calories in - calories out"


I started reading and listening to Jason Fung’s explanation of body internal system [1]. What actually influences weight is hormonal cycles. I am experiencing positive results so far, working on this explanation.

Take steps to reduce not only amount of insulin presence in blood stream, but reduce its sustained presence. Reduce visceral fat.

The problem is solved by mix of correct nutrition, moderate physical lifestyle and intermittent fasting. Never by “dieting” or sustained calorific deficit.

Fasting should not be primarily thought of as reducing calories. Rather as creating longer gap inside body without insulin running though blood stream and toggling body to use fat as metabolism source. Weight loss (from fat reduction, not muscle) is secondary benefit.

[1] https://youtu.be/RL8x7FTSo-Y


The only way those interventions work though is because their net result is less calories consumed versus expended. It's cool if that works for you, but if you've lost weight you very much have sustained a caloric deficit.


Incredibly stupid study. 800 calories a day is not a diet, it is starvation. Of course metabolic rate is going to slow way down.


I think it has more to do with how fast you lose it than how few calories you eat. The Biggest Loser contestants ate 1200-1500 calorie diets and still had abnormally low BMR even 5-10 years out.


You've mentioned the biggest loser study a few times, but my understanding is the metabolic adaptation of BMR is thought to be due to their dramatic increase in physical activity, not just the caloric restriction

https://onlinelibrary.wiley.com/doi/epdf/10.1002/oby.23308


Yes, that is what I was referring to. Although I think it was though to have more to do with the dramatic weight loss rather than the increase in physical activity or caloric restriction.

1200-1500 calories is a very reasonable daily restriction.


For weight loss, through a decade of research and trial and error, here's what I have found.

- eat more than your BMR (basal metabolic rate) but less than your TDEE (total daily energy expenditure) in order to maintain your BMR as you lose weight

- the gap between BMR and TDEE can be increased with exercise

- cardio burns calories but weight/resistance training helps build/maintain muscle mass as one's body drops weight, hopefully more from fats

- every week or so, resetting one's system by eating a very high calorie or carb heavy meal helps jolt the system as well as one's mindset. I personally find it easy to stick to good eating habits if I eat like shit once a week (on purpose, rather than accident).


This was one of my hopes for the new "weight loss drugs" like smeglitude, etc. But in reading about them they don't seem to act on metabolic rate, but just really cut the desire to eat food. So they work by calorie restriction at the end of the day vs actually changing metabolism?

Am I wrong here?

After reading the reviews of the drug, I decided to just do calorie counting of everything entering my mouth. Down 20 pounds so far in a month or so...


Things that change your actual metabolic rate are scarier. Like DNP. Ultimately the increased calorie expenditure needs to be spent somewhere and if it isn't just heat then it would have be be a large increase in NEEE (i.e. you get jittery) or I dunno, maybe you just get the compulsion to go on runs or do chores or just perfuntory tasks (like meth heads)


Old news, more low quality posts.


This [1] presentation by Robert Lustig is dense packed with quality insights.

Surrounding daily life with sugar, carbs is the root.

[1] https://youtu.be/dBnniua6-oM


Well yes, if I was 110 kg and go down to 80 kg, then my BMR will go down of course, as there is “less body” to support so to speak.


Yes, but how much will it go down? Will it go down proportionally? What more and more studies are finding is that it goes down very significantly and can stay very low for many years, making it near impossible to keep weight off.

The "Biggest Loser" study found that many of the people who lost weight on the show had a BMR much lower than other people of similar characteristics, but who had always been that size.

In other words, many times, the smug skinny person saying it's as simple as "calories in / calories out" doesn't realize that the people they are preaching to have to eat fewer calories and/or workout more than the lifelong skinny person has ever had to just to maintain a similar weight. Simply because at some point in their life, even 5-10 years prior, they were once overweight.


In my personal experience, yes it does go down quite a bit. But I also wonder if having a lower than average BMR to begin with predisposes to becoming overweight.

To make matters worse, how much you burn during exercise goes down substantially as well.

But in the end, the only thing I found for myself to work is to always track my weight and what I eat. So I’m always in control basically, no matter if my BMR is average or lower (or higher). And that’s all that counts at the end of the day.


That's it, and some of the coverage of the biggest loser followups I simply find hard to believe, like one contestant years later having to limit food to 800 cal a day to maintain a healthy weight. I'll be my life savings that wouldn't be borne out if they put the patient in a metabolic ward and actually measured expenditure.




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