Ketogenic diet but not free-sugar restriction alters glucose tolerance, lipid metabolism, peripheral tissue phenotype, and gut microbiome: RCT

(Ian Jones) #1

Just seen this study. Quite complicated for me and not sure whether it’s bad news or not. Can anyone smarter than me critique this please?

https://www.cell.com/cell-reports-medicine/fulltext/S2666-3791(24)00381-1?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2666379124003811%3Fshowall%3Dtrue

(KM) #2

They basically took 60 people, divided them into three groups, and told them to cut out just added sugar, cut out carbohydrates including any added sugar, or just eat what they always eat. The subjects self reported what they ate for 12 weeks.

Welcome to the forums! Please don’t take this the wrong way, I’m hoping one of our science minds will chime in with an analysis of the study, but any outcome from a study this small, for this short a period of time, that doesn’t control for dietary variables other than giving people a general guideline of what to eat, and relies on self reporting isn’t going to tell us much.

Some of what’s being said here is not on its face good news, but on the other hand, there’s a lot of disagreement over what the results actually mean. For example, the ketogenic dieters (who likely ate more saturated fat / meat to compensate for the lack of carbs, but who knows, the actual contents of their diet weren’t controlled or reported to us) had an increase in LDL. But is this actually a bad thing? When we deep dive into cholesterol, higher levels of LDL are actually associated with longer lifespan. (Edit, I originally said “lower levels”, which was the opposite of what I meant.)

(Ian Jones) #3

Thanks, yeah, that was pretty much all I could extract from. The thing that worried me was the effect on gut fauna. But as you see, it seems like too limited a trial to take meaningful conclusions on anything really.

(KM) #4

Yeah. The other thing is, we really don’t know much about gut fauna. It stands to reason that if you don’t eat sugar, you’re going to lose the gut bacteria that thrive on sugar, leading to “less diversity”. But is that a bad thing, or are those bacteria some we’d prefer not to have, or at least a neutral outcome (like, if I move from Fairbanks to Phoenix, and someone steals my snow tires, is that still a problem?)

(Bob M) #5

Ha! That’s good.

(Bob M) #6

Just a note. Here’s one of their figures. It appears that blood sugar at 12 weeks is worse for the low carb folks (lowcho), but that’s because there’s no first phase insulin response. There are two phases of insulin response, one first phase that’s immediate and based on what you’ve been eating, and a second phase based on what you ate, but it’s delayed. If you’re not eating carbs, your first phase response will be low to non-existent. So, your blood sugar will be higher than someone who eats carbs. Not a big deal, but it will make you look bad in a figure like this.

image

(Bob M) #7

Oh yeah, I stayed out of the “biome” discussion. The biome does…something.

For instance, I think what happened was that the biome became less diverse for the low carb folks. They think that is “bad” because? There’s evidence that aboriginals and the like have a varied biome, but does that mean a less varied biome is bad? I don’t think so, but you’ll find plenty of people who do believe this.

As @kib1 stated, if you eat less sugar, you’re likely to get a biome that doesn’t feed on sugar, which means your biome could be less diverse. But is that meaningful? I doubt it.

(Ian Jones) #8

Welll spotted!

(Cathy) #9

The lipid hypothesis is just that … a hypothesis and I might add, quite flawed.

(You've tried everything else; why not try bacon?) #10

Welcome to the forums! You’ve started out nicely.

Okay, a couple of points here: first, as @kib1 has pointed out, the study is underpowered. It will be hard to separate signal from noise. Second, nobody really knows what the gut fauna do or what effect they have on our health, and anyone who makes claims to know is only guessing. They might be right or wrong, but there are not any definitive data so far.

Thirdly, and this is a general point to bear in mind when reading any such study, is that the effect size must be taken into account. Many studies purport to show a significant statistical effect, but the clinical effect is minimal. Look at the seriousness of the condition they want to treat and its incidence in the population. If the effect size is not at least 2.0, then the study can safely be disregarded.

I suspect that this was a pilot study, aimed at testing the methodology. If the results appear reasonable, then a larger study of more people would be needed, if we want to draw real conclusions.

(KM) #11

Another issue with this study, they make a big deal about the lowcho folks eating fewer calories (100 less per day) as a way of explaining modest weight loss. I don’t know how that can really be ascertained with self reporting. It’s notoriously difficult to accurately estimate the calorie content of unprocessed fatty meat, which I will reasonably assume people might be eating if they’re cutting out carbs, because even the same cut can easily have an extra 100 calories of fat (about a tablespoon) or more. Same with bacon - just how streaky is it? The reporting and even the calorie content on the package or the internet is an average, it’s not like they analyze every steak!

The overall premise is good but I’m not sure the methodology is ever going to be all that scientifically useful.

(Kirk Wolak) #12

And that looking bad. Is the Tobacco Company Equivalent of “Muddying the Waters”.

The more studies they can do, that give Keto and shade. The more they will do.

We are a threat to a TRILLION DOLLAR industry. Imagine if going to the store, the “heavily processed” foods were 90% reduced. That would be 1 aisle in the middle.