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

J

Jaybee00

Senior Member (Voting Rights)

Significance​

Economic development is associated with increased prevalence of obesity and related health problems, but the relative importance of increased caloric intake and reduced energy expenditure remains unresolved. We show that daily energy expenditures are greater in developed populations, and activity energy expenditures are not reduced in more industrialized populations, challenging the hypothesis that decreased physical activity contributes to rises in obesity with economic development. Instead, our results suggest that dietary intake plays a far greater role than reduced expenditure in the elevated prevalence of obesity associated with economic development.

Abstract​

Global economic development has been associated with an increased prevalence of obesity and related health problems. Increased caloric intake and reduced energy expenditure are both cited as development-related contributors to the obesity crisis, but their relative importance remains unresolved. Here, we examine energy expenditure and two measures of obesity (body fat percentage and body mass index, BMI) for 4,213 adults from 34 populations across six continents and a wide range of lifestyles and economies, including hunter-gatherer, pastoralist, farming, and industrialized populations. Economic development was positively associated with greater body mass, BMI, and body fat, but also with greater total, basal, and activity energy expenditure. Body size–adjusted total and basal energy expenditures both decreased approximately 6 to 11% with increasing economic development, but were highly variable among populations and did not correspond closely with lifestyle. Body size–adjusted total energy expenditure was negatively, but weakly, associated with measures of obesity, accounting for roughly one-tenth of the elevated body fat percentage and BMI associated with economic development. In contrast, estimated energy intake was greater in economically developed populations, and in populations with available data (n = 25), the percentage of ultraprocessed food in the diet was associated with body fat percentage, suggesting that dietary intake plays a far greater role than reduced energy expenditure in obesity related to economic development.

 
Not very surprising.

The rural seaside town of Woodbridge has a high obesity rate, and an even higher overweight rate and these people are walking up and down the seafront and the shopping streets. Last week we met a very overweight young woman about to cross the north sea in a small sailing boat overnight in a force 6 wind. No way is that couch potato behaviour. Walk in to a supermarket and you see what the problem is.
 
We are so rich now we can afford far far more calories than we need. But is that the whole story? The question of whether there's any more to it than simply caloric intake is one that is endlessly fascinating to me.

The reason I'm fascinated is because answer is almost certainly: yes, there is more to it than that.

There are weird quirks in obesity prevalence:
  • France (17% obese) is consdierably less obese than the UK (26%) . That's not about wealth.
  • Colorado (25% obese) is so much thinner than Kansas (36%), which is next door, and Oregon (33%), which is similarly white and rich.
  • Egypt and Vietname have similar GDP per capita but Egypt (39.8% obese) would absolutely dominate Vietnam (2.1% obese) in a sumo competition.
In my view cultural factors determining what foods are eaten probably matter. Because - and this part is important - the foods themselves matter. A calorie is unlikely to simply be a calorie, from an obesity standpoint. I'm certainly open to
- a seed oil hypothesis (these were rare in the diet 100 years ago), and also
- a hyper-palatability hypothesis (I can eat a whole pack of nacho cheese doritos but not a whole bag of almonds), but also
- an environmental contamination hypothesis (a fun one is lithium - we started mining and refining that about 60 years ago and it is shown to cause obesity very very clearly in psychiatric practice).
 
Yes, quite clear that it is not just quantity of calories that count, but quality too. If it was only about quantity then we could just eat a couple of handfuls of sugar a day and be done with it.
 
Murph said:
We are so rich now we can afford far far more calories than we need. But is that the whole story? The question of whether there's any more to it than simply caloric intake is one that is endlessly fascinating to me.
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The cause is obviously the processed foods, the industrially produced foods designed to be irresistible, the sugar, the additives.

Also the easy access to these foods.
 
Murph said:
A calorie is unlikely to simply be a calorie, from an obesity standpoint.
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I doubt that. OK, there are nuanced issues over metabolic pathways but a calorie is a calorie. Obesity is due to ingesting more calories than you need. Period.

That is not to say that the reason for eating too much is simple. It presumably has a lot to do with culture and flavour. My guess is that it is simply that high levels of either sugar or salt blended with fat overcome normal satiety mechanisms. Which is how toffee, crisps, and then Pringles and Mars bars came into being. Add in a hint of vanilla, cinammon, bacon or whatever flavour and a hi-tech texturising and nobody can stop eating.
 
Jonathan Edwards said:
I doubt that. OK, there are nuanced issues over metabolic pathways but a calorie is a calorie. Obesity is due to ingesting more calories than you need. Period.

That is not to say that the reason for eating too much is simple. It presumably has a lot to do with culture and flavour. My guess is that it is simply that high levels of either sugar or salt blended with fat overcome normal satiety mechanisms. Which is how toffee, crisps, and then Pringles and Mars bars came into being. Add in a hint of vanilla, cinammon, bacon or whatever flavour and a hi-tech texturising and nobody can stop eating.
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Are there no factors that affect the metabolism in a way that down-prioritises the use of fat - essentially making it more difficult for some to loose weight or easier to gain weight?

Anti-depressants come to mind. I’ve observed people that rapidly gain tens of kilos of weight when starting them, despite not changing their diet and moving more.
 
Utsikt said:
Are there no factors that affect the metabolism in a way that down-prioritises the use of fat - essentially making it more difficult for some to loose weight or easier to gain weight?
Click to expand...

There may be lots of things that affect how hungry you are at a given weight. But that is a separate issue from calories. You put on weight if you take in more calories than you are burning.
 
I know plenty of people who would count as obese who eat even less calories than I do, going above and beyond to eat well, and have maintained this for months or years, being shamed relentlessly about how lack of discipline must be the cause of their weight.

Despite this their weight barely changes, or it constantly yoyos so that they lose a few pounds and then start gaining even more despite continuing to increase activity and decrease food intake.

It’s received wisdom that the simple ratio of food intake to expenditure is the driving factor of weight, and one that deserves challenge. The literature on obesity and weight loss is as rife with methodological issues and instances of projecting a narrative onto data that doesn’t support it as the BPS narrative of ME/CFS—it took me several years to realize that because of how deeply ingrained those biases are.
 
jnmaciuch said:
I know plenty of people who would count as obese who eat even less calories than I do, going above and beyond to eat well, and have maintained this for months or years, being shamed relentlessly about how lack of discipline must be the cause of their weight.

Despite this their weight barely changes, or it constantly yoyos so that they lose a few pounds and then start gaining even more despite continuing to increase activity and decrease food intake.

It’s received wisdom that the simple ratio of food intake to expenditure is the driving factor of weight, and one that deserves challenge. The literature on obesity and weight loss is as rife with methodological issues and instances of projecting a narrative onto data that doesn’t support it as the BPS narrative of ME/CFS—it took me several years to realize that because of how deeply ingrained those biases are.
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How does that work in terms of the physics? Have their bodies shifted into some kind of hyper-efficient state that allows them to do more work from less energy input for the metabolic processes?
 
Utsikt said:
How does that work in terms of the physics? Have their bodies shifted into some kind of hyper-efficient state that allows them to do more work from less energy input for the metabolic processes?
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The answer I came to after investing a lot of time in studying metabolism is that the body is far from a simple machine, and the thousands of processes under the umbrella of “metabolism” have multiple layers of regulation that change what processes are occurring at what times, at what rates, with what specific fuel source, using which method of ATP production with which efficiency. It’s something that seems like it should be logical from a purely physics perspective, but becomes basically an incoherent concept at the level of an organism.

[edit: to answer your question, biomedical science knows a lot about metabolism, but still does not have comprehensive understanding of weight regulation in humans]

I will leave it at that since I don’t have much time today and doing an exhaustive analysis of this topic is a massive undertaking that other people have already done much better than I ever could.

I don’t expect anyone to just take my word for it, but I do invite people to rethink the narratives that we all have internalized as “common sense” with regards to weight.

I realized a few years ago that it was a terrible thing for me to walk around believing that every overweight person I saw simply hadn’t figured out the logic of balancing caloric intake with expenditure, or simply wasn’t making the right choices with enough discipline according to that “logic”. Especially since I had just started to experience people projecting narratives of how I simply must be inflicting ill health on myself.
 
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jnmaciuch said:
The answer I came to after investing a lot of time in studying metabolism is that the body is far from a simple machine, and the thousands of processes under the umbrella of “metabolism” have multiple layers of regulation that change what processes are occurring at what times, at what rates, with what specific fuel source, using which method of ATP production with which efficiency. It’s something that seems like it should be logical from a purely physics perspective, but becomes basically an incoherent concept at the level of an organism.
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Edit: this more of a question to everyone since you said you don’t have the time.

In terms of physics, are there other ways for the body to be able to maintain the same composition while lowering the intake of energy from food and/or increasing the activity level, than a combination of
1. extracting more energy from the food when it passes through the body,
2. producing more usable energy from the same input,
3. improving the effectiveness of processes that utilises the usable energy, and/or
4. reducing energy-demanding processes that don’t lead to movement?

1 and 2 are calories in, 3 and 4 calories out.

But even if these mechanisms are at play - doesn’t physics put an upper limit to how much can be done for any given food intake? And when the food eventually runs out, the body turnes to its energy storages (that includes fat).

That would, in principle, mean that weight loss occurs when a sufficient calorie deficit is maintained.

Edit: sufficient is the key.
jnmaciuch said:
I realized a few years ago that it was a terrible thing for me to walk around believing that every overweight person I saw simply hadn’t figured out the logic of balancing caloric intake with expenditure, or simply wasn’t making the right choices with enough discipline according to that “logic”.
Click to expand...
My rudimentary understanding is that there are mechanisms that makes it so you feel more hungry, that the cravings are stronger, etc., that essentially makes it a lot more difficult to avoid food compared to someone with a «normal» weight. And there might be mechanisms that do the same in terms of physical activity.

So it isn’t a character flaw to be obese, you’re dealing with completely different circumstances.
 
Utsikt said:
My rudimentary understanding is that there are mechanisms that makes it so you feel more hungry, that the cravings are stronger, etc., that essentially makes it a lot more difficult to avoid food compared to someone with a «normal» weight. And there might be mechanisms that do the same in terms of physical activity.

So it isn’t a character flaw to be obese, you’re dealing with completely different circumstances.
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That might be part of it, though like I said, I have plenty of examples of people whose jobs keep them on their feet much more than me and certainly have less snacks and smaller meals than me, and yet will still be 100-200 lbs heavier than me.

I will try to respond to your other points later today if others don’t get there first!
 
I think it is very hard to know what someone else’s actual calorie intake is. Cravings can be very strong and hard to ignore, not everyone will admit to themselves let alone other people if they have cracked and eaten bad stuff or extra portions of normal food. If your body doesn’t tell you you’re full you are likely to seriously overeat possibly being somewhat unaware how bad the situation is. It is a very complex topic. I speak as someone with a bmi in obese range
 
Plus expectations for healthy calory intake set by the last generation or during youth are not necessarily right for this generation or adulthood once you have stopped growing.

We are a lot warmer now than we used to be, thanks to better clothing and central heating not to mention global warming. These all reduce calorific use. I felt like I spent the first 20 years of my life freezing cold.

I agree one's own hunger impulse can be hard to tame, having had to tackle weight gain myself, a couple of decades ago, after realising my BMI had crept up to about 27.

Once it became obvious something had to change I got some scales and reduced my food intake until I began to lose weight. I was shocked not to mention disappointed at how little I could eat each day to continue losing weight. I had definitely been overconsuming. Devised a little mantra "hunger is my friend" to remind me when sitting near the kitchen with a growling stomach, that the growling was helping me lose weight. Took a few years to go from BMI 27 to 21 where I am now. Scales remain the arbiters of snack permissions!
 
My only experience here is my own. I know that when I tracked everything I put into my mouth for months and made sure it was less than my roughly estimated need, my weight decreased.

When I stopped tracking and aiming for a deficit, my weight stabilised and eventually increased when I stopped being able to make my own food and ended up consuming more calories.
 
I'm close to being underweight and I believe this is in good part due to my eating habits.

I used to have problems with reactive hypoglycemia and this led to me beginning to avoid foods that cause a rapid rise in glucose, followed by a drop. This drop will trigger a craving for food that is very hard to resist. I believe this is a survival mechanism meant to increase blood sugar that is dropping too rapidly. The drop in blood sugar can be bad enough to cause hypoglycemia, but it doesn't need to get that bad to have negative consequences. If it happens occasionally, it's negligible, but if one were to follow a diet that leads to these drops in blood sugar several times a day it would cause chronic stress on the body and I suspect it might lead to metabolic adaptations that favor obesity.

I think a lot of people are stuck in this blood sugar rollercoaster, essentially trapped in a form of addiction, which is hard to get out of in an environment where foods with high simple refined carbohydrate content are sold everywhere and there's often little time for a healthy meal.

I don't drink soft drinks. I very rarely eat foods with added sugar, and when I do, it's something that isn't too rapidly digested, like chocolate, or a cake with enough protein and fats. I make sure to eat vegetables twice a day, and to have enough fibre in the diet. If a good portion of the foods that one eats consists of vegetables it's difficult to get fat. I often eat simple homecooked meals, sometimes I cook more elaborate recipes.

There was also this NIH study that found a diet of ultraprocessed foods lead to increased weight gain in comparison to people being given unprocessed foods of the same type and calorie content.

I also think that ideas from the 1950's still have a lot of influence. The good old food pyramid was created at a time when people were much more physically active and not having enough to eat was a scenario that could actually occur.
 
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