Leah:
Hello and welcome to the Ideal Nutrition Podcast. I’m Leah Higl and I am here with my co-host Aidan Muir. And today we are doing episode 129 and we are going to be talking about about L -Carnitine and fat loss. So briefly touching on what L -Carnitine is. So it is a naturally occurring amino acid that has been proposed to help with a wide variety of things. But for, what a lot of people take it for is around this fat loss stuff. So in this podcast, we’re going to talk about how effective it is from a fat loss perspective, potential mechanisms, and the research that is currently available.
From a mechanistic point of view, L-carnitine helps with fat transportation in the body. Specifically, it transports fatty acids to the mitochondria. This is part of why people are interested in L-carnitine around fat loss. Although obviously this fat transportation does not necessarily directly translate to fat loss potentially. So even though there is this mechanism, it’s like how much does this actually contribute to fat loss if at all?
Aidan:
So the easiest way for us to look outcome specifically is just looking at all the randomised controlled trials that have been done comparing L-carnitine to a placebo. And a review from 2016 did look at this. They found nine RCTs that were worth looking at. And they found an average of 1.36 kilos lost while taking L-carnitine in comparison to a placebo. A positive interpretation of that is that 1.3 kilos is better than zero. But there is some reason for skepticism.
Leah:
For sure. And looking at those specific reasons for skepticism, there was a study that had 36 women and five participants completely dropped out due to nausea and diarrhoea. That’s pretty relevant because if we’re looking at the results from a research study, if there’s that dropout, is it just kind of like survivor bias when we’re talking about like end result?
Aidan:
And also like how many people had nausea and diarrhoea just at lower levels?
Leah:
The other one that we should always think about when it comes to supplements, even just like briefly is the publication bias in regards to funding and things like that. So that’s a deep rabbit hole to go down, but something to just question.
Aidan:
Yeah. And then a big, big issue is absorption levels. So absorption levels of L-carnitine if consumed orally, which is what we are talking about are super low on average. And if it is barely absorbed, how would it help? Like if it’s barely absorbed, it’s not even going to increase that fat transportation thing that we’re talking about that doesn’t even necessarily line up with fat loss. So, adding context, greater than 95% of the body’s carnitine is located within the muscle.
People who are plant -based have lower intakes of carnitine and carnitine precursors, so they therefore have lower baseline levels. And we know that people who are plant -based get better absorption of carnitine or L -carnitine supplements. One study on omnivores found that, actually, sorry, one study just looking at carnitine supplementation in general, they supplemented two grams per day for 12 weeks, and there was no difference at the end of it in muscle stores and omnivores. There had no difference.
The people who were vegetarians though, they had a 13% increase in muscle stores. So it’s a bit of an indicator that the lower your stores are at the baseline, the more likely you are to benefit from it. But let’s just circle back to the omnivores one. Zero change. How is it doing anything? That’s one huge reason for skepticism basically. But that’s solely looking at oral consumption of it.
Leah:
For sure. So we can talk around ways, I guess around those absorption issues. So firstly, the absorption issue is obviously less of a factor if you are plant based and you’re getting less through your dietary intake, so you’re not eating those animal based products. But there are some other ways around it. One study looking at L-carnitine usage used two grams of L-carnitine alongside 80 grams of simple carbohydrates two times per day.
So double those amounts, so four grams of L -carnitine in total and 160 grams of simple carbs. The participants here were omnivores, so they weren’t plant -based or anything like that and their carnitine stores did increase by 21%. So a huge difference by adding in this other factor of carbohydrates alongside the L-carnitine.
The issue here is like pretty clear is that like you had to add 160 grams of simple carbs, like sugar to your diet to get that kind of 21% increase in carnitine stores. And is this going to be counterproductive to fat loss? Probably yes. Yeah.
Aidan:
Yeah. It’s just massively doing a lot to get a small increase in carnitine.
Leah:
Yeah. It just like, it is very counterproductive. So it’s, it’s not really, whilst we are seeing this increase carnitine stores, not really worth it. Another way around this could be looking at injecting carnitine instead of taking oral supplementation, but this is like wildly out of like our field. So not something we’re recommending, but it would be a way around the absorption issue.
Aidan:
Yeah. And that’s where it gets interesting as well, cause it’s like, as we, as we said earlier, if something increases fat transportation, that still doesn’t necessarily lead to more fat loss. Like this is way too complex for a Friday afternoon for us. I don’t know when it’ll be when listening. When do we put this out? Friday morning? So yeah, I don’t know. It’s Friday afternoon for you too. fat transportation doesn’t necessarily even translate to fat loss because the example I’m going to use is if you found a way to like hack the system, so you’re rarely burning glycogen and you’re almost exclusively burning body fat.
When you do eat carbs and they do get converted to glycogen, eventually your glycogen stores would increase if you massively hacked the system. This is just a thought experiment, wouldn’t actually happen in practice, but if you hacked the system, your glycogen stores would increase, but we have a limit on how much glycogen we can store. Which should therefore mean if you continue to hack the system, eventually your glycogen stores get to max capacity, and what happens if you have any glucose coming in that’s above your max capacity? has to get stored somewhere, theoretically it would be converted to body fat.
That would rarely happen, because the body would start the process of the conversion earlier on, but basically, and we simplify what it’s gonna be really complex down to this all balances out over time in most cases.
Leah:
Yeah, that’s a great summary.
Aidan:
You can’t really hack the system, but like that’s where we’re also being like, well, the carnitine injectable stuff is outside of our scope. It’s hard to say like, if that even makes a bit of a difference. There are plenty of people who use it as a PED, but it’s not even a popular PED, people using that. But oral L-carnitine supplementation, pretty rare to have much of an impact as we kind of talked about from that, just because absorption levels, although it may be more relevant if you are plant-based and may be more relevant if you are consuming a ton of carbs alongside of it.
Leah:
This has been episode 129 of the Ideal Nutrition podcast. If you haven’t yet left a rating or review, it is always greatly appreciated for you to do so, but otherwise, thanks for tuning in!