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.
Click to expand...

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.
Click to expand...

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.
Click to expand...
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.
Click to expand...
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?
Click to expand...
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.
Click to expand...
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.
 
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