Energy expenditure and obesity across the economic spectrum, McGrosky et al. 2025

[Jonathan Edwards]

The intriguing thing is that even for people who gain a lot of weight - say four stone over five years - the excess of intake is a very small percentage. Since people are of different sizes and levels of activity this small percentage is much smaller than the likely difference in requirements between people. We don't expect everyone to eat the same amount at all. The problem is eating just a bit more than that particular person needs in the context.

 

[Trish]

I don't think we can ignore other factors than calorie intake. Calorie expenditure matters too. Someone who moves about more, even if they don't think of it as 'exercise' and someone who spend more time in cold environments so needs to use energy to retain body heat can gain or lose weight without changing their diet.

I have had to cut back my intake as my ME/CFS has become more severe and I can't move around as much as when well. According to my Fitbit, I'm burning about 1,100 calories a day. Less on crash days. When I was younger and fitter before ME/CFS that was a slimming diet.

At the extremes like endurance sports and polar explorers, calorie needs are huge. Tour de France male cyclists need to stuff in 6000 calories a day and have detailed diet and energy tracking by their teams.

But even comparing 2 people who seem to have the same calorie consumption and similar lifestyle may vary greatly in actual activity and exposure to cold.

On a different angle, I never blame people who can't stick to reduced calorie diets, as I've been there myself at various phases in my life where the harder I tried to diet, the more difficult and depressing it became. It's a complicated issue.

 

[Jonathan Edwards]

I don't think we can ignore other factors than calorie intake. Calorie expenditure matters too.

Yes, that is the equation. One has to equal the other. And weight gain is always due to a slight excess of intake over the needs at the time for that person.

But even comparing 2 people who seem to have the same calorie consumption and similar lifestyle may vary greatly in actual activity and exposure to cold.

So we shouldn't even start comparing two people. All that matters is the needs of the person in question.

On a different angle, I never blame people who can't stick to reduced calorie diets

I wouldn't want to blame people, but there is no need to go there. The problem I see is raising arguments that can be interpreted as meaning that deliberately limiting food intake is not the key to the solution. The exercise people do this. They tell people that to lose weight they should go out and exercise. There is no point unless you also limit your intake in the context.

The problem is a very slight imbalance on the homeostatic control mechanism for some people. Unless you override that it will simply respond to exercise by calling for more food. If you go on a hiking holiday where the food comes in rations that works but going to exercise classes once a week, or running round the park every evening will achieve nothing without deliberate limitation when you get home.

We constantly see articles in the Guardian saying that overweight is not about eating more than you need. It is unfair to suggest that because it isn't true and it encourages people to follow habits that will get them nowhere.

 

[Utsikt]

Losing weight and maintaining weight loss isn’t a one and done thing. It’s for the rest of your life.

Eating more than you have reason to believe that you need will never lead to lasting weight loss. It simply isn’t an option.

It’s incredibly demotivating to not lose weight when you restrict your calorie intake, and it’s incredibly difficult to essentially permanently change every aspect of your life because food is so ingrained in it and the social fabric.

But it is the only option that even has a chance or succeeding. Even if there are some metabolic factors that substantially lowers the calorie need for some, eating more than you’d normally need will guarantee a failure to lose weight. It’s an absolute requirement.

Without any further comparison, you can’t just quit hard drugs for a few month or years. You have to quite them for the rest of your life. Excessive food intake is no different and maybe equally challenging.

Which is why I believe that the focus on weight in the shorter term is misguided. The focus should be on maintaining a sustainable calorie intake and finding ways to make that work with your life (society needs to make that easier to achieve). And whatever happens happens wrt weight.

Unless we have studies over 5-10 years with perfect control over the food eaten that shows that they maintain the same weight when they were supposed to be in a not insignificant deficit, we can’t say that healthy weight loss isn’t possible.

It makes sense from an evolutionary standpoint that the body will try to preserve its energy reserves for as long as possible. But does it make sense that the energy reserves can’t eventually be used?

 

[jnmaciuch]

Losing weight and maintaining weight loss isn’t a one and done thing. It’s for the rest of your life.

Eating more than you have reason to believe that you need will never lead to lasting weight loss. It simply isn’t an option.

It’s incredibly demotivating to not lose weight when you restrict your calorie intake, and it’s incredibly difficult to essentially permanently change every aspect of your life because food is so ingrained in it and the social fabric.

But it is the only option that even has a chance or succeeding. Even if there are some metabolic factors that substantially lowers the calorie need for some, eating more than you’d normally need will guarantee a failure to lose weight. It’s an absolute requirement.

Without any further comparison, you can’t just quit hard drugs for a few month or years. You have to quite them for the rest of your life. Excessive food intake is no different and maybe equally challenging.

Which is why I believe that the focus on weight in the shorter term is misguided. The focus should be on maintaining a sustainable calorie intake and finding ways to make that work with your life (society needs to make that easier to achieve). And whatever happens happens wrt weight.

Unless we have studies over 5-10 years with perfect control over the food eaten that shows that they maintain the same weight when they were supposed to be in a not insignificant deficit, we can’t say that healthy weight loss isn’t possible.

It makes sense from an evolutionary standpoint that the body will try to preserve its energy reserves for as long as possible. But does it make sense that the energy reserves can’t eventually be used?

It’s a pervasive and unfalsifiable paradigm—tell someone all the things you’ve done to try to lose weight, and they will tell you that you forgot to account for calories somewhere. It’s so easy to miss some things, after all. Spend years doing diligent calorie counts, and they will doubt the truth of those numbers. Or tell you that the problem is exactly which foods you cut out this time around and you must have incurred a nutrient deficiency and taken supplements. Or that you have to do it for 5 years instead of 3 to see any results. Have someone follow you around 24/7 to double check your calorie counting, and when you’re still at the same weight they will accuse you of being a secret eater. And through all this they’ll tell you that they don’t blame you for being fat, it’s so hard to diet after all, but there’s simply no way that the truism about calorie restriction always leading to sustainable weight loss is incorrect.

If one is absolutely certain that their paradigm is correct, it’s always possible to blame the patient (even indirectly with no awareness that this is what they are doing) and come up with an alternative explanation for the contradictory evidence. Which is a pattern that we should all recognize from a different context.

 

[Utsikt]

I would like to see tested for years in a controlled trial. Will someone eventually have a lower fat percentage (I’m assuming that’s the weight we want to lose) if they stay at the lowest sustainable calorie intake for a very, very long time?

In other words, are the metabolic shifts, etc. permanent or just long lasting? So will it eventually lead to a deficit or not?

 

[SNT Gatchaman]

The microbiome also has to play a role. All the food we eat passes through the gut and it's microbial ecosystem. It's hard to believe that it doesn't affect what happens to the calories we ingest.

It does. calories-in > calories-out -> weight gain (and vice versa) is fundamental, but we should regard "amount of food ingested" as only a proxy for calories-in.

The gut microbiome modulates the amount and nature of nutrients that cross the gut mucosal barrier, which probably represents a more accurate view of calories-in.

Effects of Gut Microbes on Nutrient Absorption and Energy Regulation (2012, Nutrition in Clinical Practice)

The Gut Microbial Regulation of Epigenetic Modification from a Metabolic Perspective (2024, International Journal of Molecular Sciences)

The complex link between the gut microbiome and obesity-associated metabolic disorders: Mechanisms and therapeutic opportunities (2024, Heliyon)

Using Gut Microbiota Modulation as a Precision Strategy Against Obesity (2025, International Journal of Molecular Sciences)

Then how come a gastric bypass surgery is extremely effective in almost all with morbid obesity patients?

Partly because a Roux-en-Y upper GI re-configuration alters the downstream gut microbiome. It's not just about reducing stomach capacity and accelerating satiety as with the alternative sleeve gastrectomy.

Effects of gastric bypass bariatric surgery on gut microbiota in patients with morbid obesity (2024, Gut Microbes)

 

[Jesse]

Partly because a Roux-en-Y upper GI re-configuration alters the downstream gut microbiome. It's not just about reducing stomach capacity and accelerating satiety as with the alternative sleeve gastrectomy.

Yeah sorry I mixed up gastric sleeve and bypass. The sleeve is also pretty effective as far as I know though.

Interesting about the microbiota changes. I'm definitely curious how relevant/important the microbiome ends up being regarding health/disease.
I think the bypass also reduces absorption?

 

[Hoopoe]

It does. calories-in > calories-out -> weight gain (and vice versa) is fundamental, but we should regard "amount of food ingested" as only a proxy for calories-in.

The gut microbiome modulates the amount and nature of nutrients that cross the gut mucosal barrier, which probably represents a more accurate view of calories-in.

And what determines the composition of the microbiome?

It's mainly a question of what we eat, not just the calories. The additives in industrially processed food can also affect the microbiome.

If you tell peope that it's just a question of calories intake versus consumption that leads to people trying to lose weight by starving themselves, futile yo-yo diets. The inevitable failures then lead to increasing hopelessness. That approaches proves to the person trying to lose weight that it's impossible, they will begin to react to the topic of weight loss with negative emotions, and eventually decide that it's best to accept that things cannot be changed.

The other problem with the it's just calories intake versus consumption is that it can lead to people believing that they can lose weight while continuing to eat junk food.

So in my opinion the weight loss framing is wrong. The goal should be to achieve greater metabolic and gut health through a balanced, healthy diet that can be indefinitely maintained with little effort. This has many benefits and a healthy weight is just one of them.

 

[Jonathan Edwards]

So what actually is this "contradictory evidence" against the idea that overweight is always due to eating more than is needed in the context (which makes all these arguments about microbiome and stuff by the by)?

All we have had so far is a suggestion that calorie counts dont tell us everything. But thats obvious because we rarely have a good estimate of usage. The argument is non sequitur again. There is no need even to calorie count. All you need to do is ensure intake of at least some food components are reduced without increasing others. I know of no evidence for that ever failing when rigorously verified. All we have heard is anecdote - pretty much like brain retraining!!

So this has nothing to do with paradigms being suspect.

 

[Hoopoe]

Framing it as mere question of calories in versus calories required has been the dominant paradigm for a long time. At the same time many countries are in an obesity epidemic. In the real world, this message is ineffective in solving the problem. It's not wrong, just too simplistic. It's also not threatening to food industry serving us the obesity promoting foods at every corner.

Let's educate people to eat healthy balanced meals instead of telling them they need to limit calories.

 

[Turtle]

Another anecdote. I recently gained weight because of diabetes pills. Side-effect in 1 - 3 out of 10.
I lost 15 kg 6 years ago and now the same low-carb diet didn't work. It's driving me to the hopelessness @Hoopoe mentioned.
Am I supposed to "know" how to handle this? The docs pills working against me? Glucose higher one more pill, a perpetuum mobile?

 

[Utsikt]

So what actually is this "contradictory evidence" against the idea that overweight is always due to eating more than is needed in the context (which makes all these arguments about microbiome and stuff by the by)?

All we have had so far is a suggestion that calorie counts dont tell us everything. But thats obvious because we rarely have a good estimate of usage. The argument is non sequitur again. There is no need even to calorie count. All you need to do is ensure intake of at least some food components are reduced without increasing others. I know of no evidence for that ever failing when rigorously verified. All we have heard is anecdote - pretty much like brain retraining!!

So this has nothing to do with paradigms being suspect.

I think the suggestion has been that for some, reducing the food intake to the level that is required to achieve (further) weight loss within a few months results in adverse health effects to the extent that the diet can’t be continued.

So the question seems to be about if there are ways for everyone to lose weight without compromising their health one way or another.

My main question to that is what would happen if you stay at the lowest possible food intake that covers your nutritional needs for many years. If there are some adaptations in the short term that makes weight loss in a healthy manner impossible - do they persist for years?

 

[Hoopoe]

Another anecdote. I recently gained weight because of diabetes pills. Side-effect in 1 - 3 out of 10.

If it's type 2 diabetes then diet alone can lead to major improvement or remission.

 

[Turtle]

If it's type 2 diabetes then diet alone can lead to major improvement or remission.

Getting to a normal weight did not lead to improvement, let alone remission.

 

[Snow Leopard]

I would like to see tested for years in a controlled trial. Will someone eventually have a lower fat percentage (I’m assuming that’s the weight we want to lose) if they stay at the lowest sustainable calorie intake for a very, very long time?

In other words, are the metabolic shifts, etc. permanent or just long lasting? So will it eventually lead to a deficit or not?

I don't understand the question. Your metabolism will slow down (you will feel very cold tired and hungry and your behaviour will shift towards not exerting to conserve energy) if you have a large caloric deficit. These effects can start to be noticed with a caloric deficit of 1000+ kcal per day.

"Lowest sustainable calorie intake" suggests body weight in equilibrium.

But if someone had a deficit for a long time they would end up with dangerously low body weight or die.

Low body weight (it also depends on muscle mass) means a lower basal metabolic rate, but the difference might not be as large as some people think. So yes, this means eating a little less long-term. If people aren't getting their nutritional needs it's probably because they're not eating a balanced diet, but vitamins exist so there is a solution.

But intensity and duration of physical activity makes a difference (walking at 6 km/h for an hour is around 0.05 kg, but intense exercise can be much higher) in terms of energy used.

 

[Utsikt]

I don't understand the question. Your metabolism will slow down (you will feel very cold tired and hungry and your behaviour will shift towards not exerting to conserve energy) if you have a large caloric deficit. These effects can start to be noticed with a caloric deficit of 1000+ kcal per day.

"Lowest sustainable calorie intake" suggests body weight in equilibrium.

That’s poor phrasing by me.

By «lowest sustainable calorie intake», I meant the lowest calorie intake you can sustain over time without experiencing negative effects on your health.

I.e. is there a healthy way to lose fat for all otherwise healthy people with excess fat?

But if someone had a deficit for a long time they would end up with dangerously low body weight or die.

It was meant for a scenario where someone with a substantial amount of excess fat was in a substantial calorie deficit but didn’t lose weight, which is what jnmaciuch has claimed can be the case.

I’m not talking about going further once you’re at a more balanced body composition (or your muscles start increasing your weight due to exercise).

 

[Snow Leopard]

That’s poor phrasing by me.

By «lowest sustainable calorie intake», I meant the lowest calorie intake you can sustain over time without experiencing negative effects on your health.

I.e. is there a healthy way to lose fat for all otherwise healthy people with excess fat?

Yes, I've lost 18 kg in the last 7 months. That is the edge limit of what I think is possible/healthy and I supplemented with multivitamins and made sure I had at least some protein, vegetables etc each day.

With a genuine caloric deficit, you will lose weight guaranteed, I have zero doubts about this. But it is hard to predict exactly what your caloric intake and expenditure is on a day to day basis. So I think that is why some people (including myself) tend to overcompensate with the deficit so that we can see a clear change over the week (differences in fluid weight creates a lot of noise if you measure your weight every day and some people may misinterpret this)

I've stopped now for other reasons and will cycle my weight down a few kg if it creeps up again.

 

[Sean]

Yes, I've lost 18 kg in the last 7 months.

That is both impressive and somehow a little scary.

(differences in fluid weight creates a lot of noise if you measure your weight every day and some people may misinterpret this)

I try to standardise it and minimise data noise as much as possible by weighing myself first thing in the morning, after the morning ablutions, before any breakfast, and with no clothes on.

 

[Snow Leopard]

That is both impressive and somehow a little scary.


I try to standardise it and minimise data noise as much as possible by weighing myself first thing in the morning, after the morning ablutions, before any breakfast, and with no clothes on.

Yes, but that alone is not enough unless your climate is identical, do the same amount of activity, you eat and drink exactly the same amount every day, don't get any sort of infection, don't have any hormonal changes etc.

Really the solution is not to pay too much attention to the exact figure so long as it is trending down. There are apps that will calculate weighted moving averages or whatever if people really need a number to look at.