[jhassell]

Doesn't the risk of being overweight completely overwhelm the risk of a not-yet-understood gut flora change? We know that even being minimally overweight poses a risk; a Nurses’ Health Study reported that women with BMIs in the range of 24-24.9 had a 5-fold greater risk of diabetes when compared with women with BMIs of less than 22.

[cowmoo728]

It is possible (likely?) that the observed gut flora changes interfere with normal metabolic function, causing long term weight gain.

2020 - "future studies should consider the metabolic pathways of different artificial sweeteners. Further (long-term) human research investigating the underlying physiological pathways of different artificial sweeteners on microbiota alterations and its related metabolic pathway is warranted to evaluate the potential impact of their use on body weight control and glucose homeostasis."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7817779/

[andrewmutz]

Yes, there has been some fascinating research coming out suggesting that the gut flora composition can have a causal effect on obesity. For example, if you transplant feces from overweight humans and normal weight humans to mice, the mice will gain (or not gain) weight, depending on which person the feces came from:

https://www.science.org/doi/10.1126/science.1241214

[PuppyTailWags]

It seems that despite increased risk of diabetes, being slightly overweight actually decreases all-cause mortality and being grade 1 obese doesn't affect all-cause mortality. I heard of this through a podcast and I'm not super educated, but it seems to me that the relationship of weight and health is more complicated, since I agree that increasing risk of heart disease, diabetes, etc. is bad. It just doesn't seem to bear out in actually killing a person. Maybe it decreases their quality of life drastically instead?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4855514/

[adrianN]

I wonder whether that is true for all age groups. In very old patients, being somewhat overweight can act as an important energy reserve that allows the patient to survive an illness or a hospital visit. Younger patients generally are more robust, I assume they benefit less from a couple of extra kilos of fat.

[PuppyTailWags]

The study accounts for age and shows the phenomenon is consistent across multiple age ranges.

[DontchaKnowit]

Yes THANK YOU. This is why it is infuriating to me that elementary/middle school students are still being graded on their BMI in gym class and taught to maintain a "good" BMI. With my body composition, I would be absolutely emaciated if I was on the lower end of the "healthy" BMI range. As it is I am bordering on obese, which if you saw me in person would be completely preposterous. The BMI itself is a pretty useless metric of body fat, and body fat is a pretty useless metric for health.

[eternityforest]

Why is this such a hard question? You would think a question as ubiquitous as "What should I eat?" would have more consensus.

Some studies show extra mortality in normal to underweight people, including from common causes relevant to average people, but there's also a ton of work on calorie restriction?

Is low BMI dangerous, or does it just commonly go along with a lifestyle that might lead to injuries and rhabdomyolysis and a case of diarrhoea in a place without hospitals?

It would be interesting to see adventurousness treated as a separate category for controls.

In the past there was no fridge, people stored their own energy, and there was no pepper spray and cops and forklifts, exercise programs had the extra constraint of physical activity being directly needed to survive.

What amount and type of activity should a modern person who has reason to believe they'll probably never be in a serious fair fight with no weapons or need to walk 3 days to get help do?

How much should someone eat when they do not ever plan to drink untreated water or go somewhere away from medical help if they catch some parasite that causes rapid weight loss?

Is the ideal profile of nutrition changed for someone who will not be exposed to woodsmoke, bacterial illness, etc?

And then furthermore, if higher BMI isn't helpful by itself, what should people who ARE in poverty or otherwise exposed to more stresses do?

Is there a subgroup that needs a metabolic reserve? Should those people eat less to save money and be able to DoorDash if needed and have external reserves like people without poverty or adventurousness?

Or is there a real independent benefit to some level of fat?

[stnmtn]

̶R̶e̶a̶d̶i̶n̶g̶ ̶t̶h̶i̶s̶ ̶s̶t̶u̶d̶y̶,̶ ̶I̶ ̶b̶e̶l̶i̶e̶v̶e̶ ̶y̶o̶u̶ ̶a̶r̶e̶ ̶m̶i̶s̶i̶n̶t̶e̶r̶p̶r̶e̶t̶i̶n̶g̶ ̶t̶h̶e̶ ̶r̶e̶s̶u̶l̶t̶s̶.̶ ̶I̶t̶ ̶s̶a̶y̶s̶ ̶n̶o̶t̶h̶i̶n̶g̶ ̶a̶b̶o̶u̶t̶ ̶i̶f̶ ̶b̶e̶i̶n̶g̶ ̶o̶v̶e̶r̶w̶e̶i̶g̶h̶t̶ ̶d̶e̶c̶r̶e̶a̶s̶e̶s̶ ̶a̶l̶l̶-̶c̶a̶u̶s̶e̶ ̶m̶o̶r̶t̶a̶l̶i̶t̶y̶ ̶r̶e̶l̶a̶t̶i̶v̶e̶ ̶t̶o̶ ̶n̶o̶r̶m̶a̶l̶ ̶w̶e̶i̶g̶h̶t̶.̶ ̶I̶t̶ ̶o̶n̶l̶y̶ ̶s̶a̶y̶s̶ ̶b̶e̶i̶n̶g̶ ̶o̶v̶e̶r̶w̶e̶i̶g̶h̶t̶ ̶d̶e̶c̶r̶e̶a̶s̶e̶s̶ ̶a̶l̶l̶-̶c̶a̶u̶s̶e̶ ̶m̶o̶r̶t̶a̶l̶i̶t̶y̶ ̶r̶e̶l̶a̶t̶i̶v̶e̶ ̶t̶o̶ ̶o̶b̶e̶s̶i̶t̶y̶.̶ ̶ ̶T̶h̶a̶t̶ ̶i̶s̶ ̶h̶o̶w̶ ̶I̶ ̶r̶e̶a̶d̶ ̶i̶t̶ ̶a̶t̶ ̶l̶e̶a̶s̶t̶,̶ ̶I̶ ̶c̶a̶n̶'̶t̶ ̶f̶i̶n̶d̶ ̶a̶ ̶b̶a̶s̶e̶l̶i̶n̶e̶ ̶f̶o̶r̶ ̶t̶h̶e̶ ̶H̶R̶ ̶o̶f̶ ̶a̶ ̶n̶o̶r̶m̶a̶l̶ ̶w̶e̶i̶g̶h̶t̶ ̶i̶n̶ ̶t̶h̶e̶ ̶s̶t̶u̶d̶y̶ ̶l̶i̶n̶k̶e̶d̶.̶

edit: this is wrong, see reply below

[PuppyTailWags]

The article explicitly compares overweight, grade 1 obesity, grade 2 & 3 obesity together, obesity generally, relative to normal weight.

> Random-effects summary all-cause mortality HRs for overweight (BMI of 25–<30), obesity (BMI of ≥30), grade 1 obesity (BMI of 30–<35), and grades 2 and 3 obesity (BMI of ≥35) were calculated relative to normal weight (BMI of 18.5–<25).

[stnmtn]

Great point, I completely misread that. Edited my original comment!

[PuppyTailWags]

Yeah I had to read this a few times too! I was totally baffled by having 3 categories for obesity, but one of the categories is grade 2 & 3 categories together, and one of the categories is grade 1, 2, & 3 together.

[thisismyswamp]

I think the catch with this study is that BMI is different from muscle mass and fat mass.

Higher BMI can simply mean more athletic.

I wish we could tell!

[awestroke]

False dichonomy; you can choose to consume neither sugar nor sweeteners

[SoftTalker]

Yep. I used to drink a lot of diet soda. I stopped that probably 10 years ago or so. I don't use artificial sweeteners in anything. I mostly drink water now. When I drink coffee or tea it's unsweetened. For an occasional treat such as a milkshake I will use sugar, sparingly.

Incidentally, when I drink diet soft drinks now they taste like chemicals. Completely unnatural sweetness. I don't find them enjoyable at all. But when I used to drink them daily, I liked them, really almost craved them.

[SamPatt]

Other than natural sugars in fruit, my diet has effectively no sugar or sweeteners.

It's not that hard after several years of changing your eating habits slowly.

It helps that I've always preferred drinking water.

[Al-Khwarizmi]

That, and it's also possible to consume (moderate amounts of) sugar and have a good BMI.

[yamtaddle]

Gut flora probably affect calorie and nutrient absorption. It seems worth checking whether the gut flora changes increase calorie absorption or cause increased appetite (say, by causing nutrient deficiency) before deciding which path is better for weight loss.

[matthewdgreen]

The issue is not necessarily just nutrient absorption, but also the body's production of GLP-1: that influences appetite and blood sugar regulation. https://pubmed.ncbi.nlm.nih.gov/33820962/

[docandrew]

Any change in absorption is going to be minuscule in comparison to the difference in calories one gets from all the excess sugar.

Anecdotally, switching from full-sugar soda to diet has been a hugely beneficial change to my own health. Would water be better? Maybe, but I’ll settle for harm reduction.

[hinkley]

I switched from soda to tea three or four times in my life before swearing off soda entirely. Lost 10 lbs every time.

The problem with artificial sweeteners is that we have “taste buds” for sweet in our intestines, and there’s a theory that reacting to that increases absorption, so your body pulls more carbs from French fries you ate with your Diet Coke.

This is likely a big part of why lecturing people about CICO is such a dick move.

“Calories” in food are net calories, not gross calories. We didn’t calculate the calories in bread by burning it in a sensor chamber. We got it by isolating volunteers, measuring the energy in their food versus the energy in their poop, assuming the rest ends up in your body.

But of course any heat generated by gut microbes might be shed, and the hydrogen bonds in your burps are also lost calories.

I was a very gassy person when I was a young beanpole. Not so much anymore.

[kenjackson]

Anecdotally my wife changed her diet and basically tried to replace sugar with sucralose wherever she could. The end result was a significant weight loss. I should note she also did start exercising more at the same time, so definitely not a controlled study. But the delta in calories from sugar was far greater than the caloric expenditure from exercise.

[hinkley]

I started long distance walking this year, and nearly every time I see the calorie count I am reminded of the aphorism about not being able to outrun a bad diet. I think that’s bullshit, with a proviso.

The provision is that you can’t outrun a bad diet by exercising a half hour a day. That 30 minutes is a number doctors settled on not to scare sedentary people into not starting an exercise program. You really need an hour or more a day.

I’m trying to get my walk route down to 90 minutes, in prep for a half marathon next year. If I stop for a matcha at the halfway point, I’ve still burned well over twice what I consumed. If I get the smoothie still come out ahead.

The real “secret” there is that when I watch TV I nibble. Not getting food on books is the only reason I don’t nibble when reading. What I’ve done in a 90 minute walk is to forestall eating more than one single thing in that ninety minutes. And lowered my stress level. Cortisol is the other killer here.

Even before that the nearest good coffee shop was a mile away and my net calories were ~100. If I avoided a certain cream based beverage.

For some people, banning prepared foods does a similar thing. Preparing a snack takes fifteen minutes instead of fifteen seconds. You just don’t have as much time in the day to stuff your face once the convenience is gone.

The other aphorism is that you lose weight at the grocery store, which I do believe. If you come home with fruit instead of pie and chips you’ve already fought half the battle.

[watwut]

Regular moderate exercise improves your health results whether you loose weight or not. It is one of the few interventions that actually have statistical results. It also affects your life positively by making you stronger or faster or just able to walk longer depending on how exactly you exercise.

If you dont care about health or improvment in things like strength stamina, then the "dont exercise it is waste" knee jerk response makes some sense. If you care about health, it does not at all.

[layer8]

> there’s a theory that reacting to that increases absorption, so your body pulls more carbs

There doesn’t seem to be any good studies about that. Anecdotally, as someone who has been drinking 2-3 liters of Diet Coke or Coke Zero daily for over two decades, I haven’t experienced such an effect.

[hinkley]

George Burns smoked cigars into his nineties. He was famous for smoking them while performing.

Anecdotes don’t mean shit for public policy.

And is this even an anecdote? Were you overweight before you started drinking diet and now you’re not, with no other lifestyle changes? Food? Mood? Exercise?

[layer8]

> Anecdotes don’t mean shit for public policy.

Right, and so yours doesn’t either.

My point is, the theory that artificial sweeteners somehow cause more “net” calorie intake doesn’t have much grounded evidence. Presenting it as a likely truth is fallacious.

[docandrew]

I thought calories were measured using a calorimeter which burns the food. I'm pretty sure nutritionists don't have armies of volunteers who eat nothing but a single ingredient for 24-hours, whose poop is then burned in a calorimeter to measure the difference?

How much increased absorption are we talking about? If I don't drink a can of Coke containing 150 calories of pure sugar, and instead drink a Diet Coke with basically 0 calories, are you saying that my gut is going to somehow grab 150 calories that it would have otherwise ignored?

[yamtaddle]

> Any change in absorption is going to be minuscule in comparison to the difference in calories one gets from all the excess sugar.

I think that depends on how much it takes to have this effect. If the equivalent of one diet soda every couple days (the doses in the article seemed pretty small to me?) is acting like a kind of pesticide, even in small doses, and killing a lot of calorie-eating gut flora, the harm might exceed the benefit. On the other hand if the artificial sweetener is replacing the sugar in 64+oz of soda per day rather than 16ish oz every couple days, sure, the benefits probably overwhelm any harm.

[googlryas]

Sure, if sugar sweetener is the only thing keeping you overweight.

But it's probably harder for your body to deal with being both overweight and having a weird gut biome simultaneously.

[pessimizer]

> Doesn't the risk of being overweight completely overwhelm the risk of a not-yet-understood gut flora change?

It's possible that becoming overweight could cause a gut flora change, or a gut flora change could make you likely to become overweight.

There's no benefit to ending research into diabetes after you find an association between overweight and diabetes, or in making an assumption that the condition of one's gut flora and being overweight are independent.

[hinkley]

In geriatric patients, being slightly overweight has better prospects than being underweight.

I’m not sure what the pathology is there, other than hitting starvation cycles if you get certain illnesses, and possibly bone density.

[narag]

Doesn't the risk of being overweight completely overwhelm the risk of a not-yet-understood gut flora change?

If you put me in that dilemma, I would choose the artificial sweeteners every single time. So yes. Diets are difficult enough.

But...

Although I distrust all the studies that seem to nudge me into stopping dieting, and the article mentions some of them that are now discredited or impossible to reproduce, I don't simply ignore them. Maybe it's "Big Sugar", as a fellow HNer called it, but maybe not.

Flora disruption seems very real to me. I had to quit Coke years ago (don't ask) and now I've quit sodas alltogether. I don't like coffee, but fortunately caffeine is sold in pills, and much cheaper.

I mention soda specifically because that's what kept me needing sweeteners. Now I drink only water, beer when out with friends, and tea, that unless I'm actively trying to lose weight, I have with one cube or nothing.

[VLM]

The local minima for diabetes is likely not the overall minima for death rate. I would be surprised if the minima for diabetes diagnosis was NOT slightly below the minima for overall death rate.

The famous JAMA article from 2013 that everyone likes to cite, including in comments below, showed no significant increase in death rate for grade 1 obesity and the effects really kicked in strongly around grade 2 and 3 obesity.

The more recent BMJ article from 2016 that no one wants to cite, showed minimum death rate in the 20-24 BMI range depending on smoking history. That paper reported the most reliable looking studies of 'non-smokers followed up for over 20 years' had a minimum total death rate at a BMI around 20-22, but that does not support the "Healthy at Every Size" narrative so its memoryholed.

I try to keep up to date on diet and supplement journal articles; there's probably journal articles newer than 2016 thats not in my notes yet.

Something EVERY study seems to agree on is the death-curve looks very U shaped kind of like computer chip hardware failure rates. The point being that studies disagree on the exact minima death rate vs BMI which is only relevant for large scale population goals, however they all agree that going from, perhaps, 22 to 23 will have an effect that although possibly measurable if across enough people, will tiny and be deep in the decimal places, whereas going from "twenties" to "forties" for BMI means the patient is unquestionably going to die very young, although EXACTLY how young may vary from study to study.

The problem with BMI of course is it was originally a screening criteria to "find the worst quartile and counsel them" but as happens with all metrics over time eventually the rough and imprecise low resolution screening criteria turned into an "optimize for its own sake" metric and people getting very weird and hyperfocused about their personal metric calculated to five sig figs at least.

[ZeroGravitas]

It does feel a bit like "Big Sugar" at work, demonising its replacement with FUD.

The way they lump them all together feels really odd to me.

It would be like a report saying non-hydrocarbon vehicles are bad for reason X. Why would anyone but the sugar industry care about all the different substitutes for sugar in such an undifferentiated way?

[rpdillon]

Last paragraph:

> They make sure to note that they’re not calling for consumption of sugar instead, because excess sugar is absolutely, positively linked to adverse health effects.

I think they care about the substitutes because that's an area where the harm is often debated and much is still unknown. They don't seem to be suggesting that sugar is preferable in any way.

[maxk42]

You're making the assumption that artificial sweeteners solve the problem of weight gain. The studies that have been conducted so far show only a minimal impact to body composition by switching from sugar to artificial sweeteners. There are more mechanisms at play than are presently understood.

[giantg2]

"Doesn't the risk of being overweight completely overwhelm the risk of a not-yet-understood gut flora change?"

Probably. However those outcomes can be achieved in ways that don't involve sugar substitutes (eg question implies a false dichotomy).

[shkkmo]

As far as we know, yes. As other commenter have noted, I wouldn't discount the potential role of gut flora changes on obesity risk. This is explicitly called out in the

This study isn't saying that everyone should stop eating artificial-sweetners. It is saying that the previous understanding that artificial sweeteners are biologically inert and risk free.

This study shows that we need to do further research to understand what the gut biome changes entail. It also suggests that we should be a more circumspect about replacing sugars in our diet without worrying about trying to reduce our overall desire for sweet foods / drinks.

[time_to_smile]

You're making the implicit assumption that sugar substitutes do reduce the risk of being overweight. At least the first post I found on the topic suggest there is evidence of "a positive correlation between regular use of artificial sweetener and weight gain"[0]

0.https://www.publichealthpost.org/research/can-sugar-substitu...

[tuatoru]

This article suggests a mechanism for that positive correlation: impairment of glycaemic response by the most commonly used artificial sweeteners.

[colordrops]

Many non overweight people eat these fake sweeteners too.

[hinkley]

You can be skinny and diabetic too.

One of the American Ninja Warriors last season wore an insulin pump. While competing. I’ve since noticed pictures of a few competitive runners with them.

Weight and metabolic function are correlated, not equivalent.

[roxymusic1973]

She was type 1 diabetic, so perhaps not relevant: https://www.diabetesselfmanagement.com/blog/an-american-ninj...

[colordrops]

That's my point. We shouldn't only be concerned about overweight people.