Episode 89 Transcript – Reasons Why You Could Be Feeling Fatigued


Hello and welcome to the Ideal Nutrition Podcast. I am Leah Higl and I’m here with my co-host Aidan Muir. And today we’ll all be talking through reasons why you may be feeling fatigued. So we will specifically be focused on nutrition aspects of fatigue. So things that we probably … or definitely not going to cover are things like sleep, general recovery, medications, specific conditions like your chronic fatigue syndrome, for example. They’re just not going to fall under the scope of what we’re talking about. We’re going to talk about specific nutrition-related things that you might want to look at if fatigue is an issue for you.


Going through them one by one, we are going to start with iron deficiency. This is the easiest one in terms of being the most obvious cause. If you feel fatigued, this is pretty much always, at least the first one you should check. Iron deficiency, anemia, affects around 15% of the world’s population. If you are already feeling fatigued, then there’s probably a higher than 15% chance that you personally might have iron deficiency anemia, more so if you are female and menstruating, more so if you are pregnant as well. But it’s always a good place to start looking, and obviously more so if you’re plant-based too, adding that to the mix as well.

And one of the reasons why I like to start there is because it’s as simple as just getting a blood test. You can check that pretty easily. As you start going through the list, there’s a lot of other things that are harder to kind of assess whether it is something that’s causing fatigue, iron deficiency is the easier one. Addressing it is harder in some cases. It’s still simple stuff, but it’s just the execution that could be harder. So increasing dietary intake of iron, that’s a topic in itself. I don’t know if we’ve written a blog post or anything like that. We definitely don’t have a podcast on that. I do think we have a blog post on iron deficiency.

Yeah, and I’ve definitely done some Instagram posts. You’ve probably done some Instagram posts.


I definitely have. But more so plant-based specific.


Yeah, so it’s worth looking at our Instagrams if you want to scroll back and find this post. And another alternative is either transfusions or supplements as well. I am a very food first person, but the logistics of getting a high dietary intake under some circumstances can be quite hard for some people. So I’m pretty pro supplementation or transfusions in a lot of people too. So it’s worth exploring all your options.


Yeah, a hundred percent. I’m big on iron infusions. Hey, especially for my plant-based people, given that sometimes supplements in really high doses can have gastrointestinal side effects. I think that’s something to note. But another thing that might be contributing to fatigue is B12 deficiency. So this is a lot more rare than iron deficiency, but it’s still relevant. It’s particularly relevant for people who don’t eat a lot or any animal products since B12 is mostly in animal products. Reportedly 6% of people in the UK and US under the age of 60 have B12 deficiency and I’d be guessing that the numbers would look pretty similar in Australia as well. And that number increases to 20% for those over the age of 60. So a little fair bit more in those older populations.

Like I said, this is going to be more relevant to plant-based people. It’s pretty rare that I will be focused on this for someone who eats a fair amount of animal products. But if someone comes to me with fatigue and they’re also plant-based, I’m checking iron, but I’m also definitely checking B12, particularly if they aren’t supplementing.

So similar to iron, this can be a addressed through increasing dietary intake if animal products are part of your diet. If they’re not so much, you will have to go with the other options, which would be supplementing or B12 injections. And you can check your B12 just through a pretty simple blood test. So you can check it on with your iron studies as well.


My understanding as to why the prevalence gets so high as people age, that 20% above the age of 60, is just because absorption levels just drop over time. And another thing that, I haven’t seen research on this in a long time, so I don’t know, but metformin. Metformin seems to increase vitamin B12 deficiency prevalency, particularly over very, very, very long term usage.

And metformin is a very common medication, has a lot of upside. There’s a lot of benefits people can get from it, but it’s just another thing to be like, okay, “If I’m on metformin, I should probably look at B12 a bit more closely as well.”

And another one is low calorie intake and/or low energy availability. Low calorie intake in general can make you feel fatigued. Calories are literally units of energy, so this is unsurprising. You can experience this for yourself. Just play around with lower calorie intake. There’s, I don’t know, some sweet spots there, like very now and then some people will be like, “Fasting makes me feel incredible,” and stuff like that. But I think on average when people drop their calorie intake, they feel more fatigued.

But looking at it from another angle, which is definitely more relevant, having a low calorie intake in relation to your activity can lead to what is known as the state of low energy availability, which can cause the body to downregulate certain functions. Stating why that happens, it’s simply because if your body doesn’t have a lot of energy to go around, the body downregulates some stuff to conserve the resources. If there’s not a lot of this to go around, it has to conserve it a little bit. A lot of functions will downregulate and that can make you feel a bit more fatigued.


Another reason why fatigue could occur is also being too lean in general. So having an exceptionally low body fat percentage can also lead to these very similar downregulations in function. So very similar to what you would, I guess, experience with low energy availability. We do see this in very lean bodybuilders who are nearing the end of their prep or at the end of their prep. And it often doesn’t reverse for quite some time post show, so they do have to put that body fat back on in order to reverse this fatigue they may be feeling.

So being too lean, I kind of want to put a definition around it, but it’s going to be pretty loose. And it’s going to be more based on what we’ve experienced as sports dieticians in our careers as well as a little bit of research around missing periods in female athletes, et cetera, et cetera. But it’s probably in that range of being under 10% of body fat for men and under 20% body fat for women, of course, it’s going to be dependent on the individual person. Like you might be slightly above that and you start to experience this, or you could be a female at 17, 18% body fat and still not have these symptoms from being too lean. So yeah, that’s going to be more of a personal individual thing, but I think having some numbers around it at least adds context.


Yeah. We were talking about this off-air, and I agree in that on the one hand I’m like, “Oh, I don’t want to give numbers because people experience this at different levels.” There are people who walk around significantly below that level. We’ll just put a cut-off at who are completely fine, no issues. But I think we’ve got to draw the line somewhere, and we’ve got to be like, “This is where it’s likely to be occurring.” And if you are below these numbers, it makes sense to pay attention to these things in yourself. Notice whether you’re experiencing any of those things and if you are, it is worth asking the question of being like, “Maybe I’m looking at all these other things.” Like maybe I’m looking for a B12 deficiency or something like that, and I keep searching for something, but the actual answer might actually be gaining body fat in some cases.

Another thing that, although this isn’t directly nutrition, it does tie in, is thyroid stuff. Having either hypothyroidism or hyperthyroidism can cause fatigue. One of the first reasons why I’m mentioning that is because it’s another simple one to get checked. You can just go see a GP, get a blood test, all of those kind of things. And I thought I’d put it out there into the world and be like, “This is something you should screen for if you are feeling fatigued.” It’s easy to check for.

But it also ties into the other point we’re talking about, particularly stage lane bodybuilders. There isn’t heaps and heaps of research on hormonal levels and stuff like that throughout body building preps and recovery and everything like that. But there is quite a few case studies where they’ve measured their bloods throughout the entire process, and it often takes as much as six months post show before their thyroid levels come back to normal. Their thyroid levels drop during the prep, and then they slowly return to normal over time.

We know that low thyroid hormones leads to a decrease in calorie expenditure. It is involved in a lot of those downregulations we were kind of talking about because the thyroid controls a lot of processes in the body, and that is part of how it ties into all of this fatigue stuff as well. So it’s like, although it’s not specifically nutrition, it’s like well, if you go into a calorie deficit forever, your thyroid function is going to decrease and it’s going to cause symptoms of fatigue. So it is tied in.


Absolutely. And going back to, I guess, more specific nutrient focus, we’ve also going to just briefly touch on vitamin D. So we would have, a couple of weeks ago now, put out an episode on vitamin D completely that we filmed today. But just quickly going over it, vitamin D deficiency has been linked with self-reported fatigue, although the link is not as strong as, again, iron or B12 deficiency with linking fatigue and the deficiency of that nutrient.

The tricky thing with vitamin D is that we also get it from the sun, which can make it irrelevant at times because what if we’re not spending as much time outside in the sun and if that was a factor in your fatigue? So there could be variables there coming into play. But to test this, there has been research that has involved supplementing vitamin D in those who are deficient, and it has found significant improvement in fatigue levels. So regardless of the sun aspect and getting outside and whatnot, there does seem to be a link between improvements in fatigue levels when you do rectify a deficiency of vitamin D.


And for those who are interested in that research, we do add a lot of stuff into the show notes. So we actually have referenced that research in the show notes. If you do want to look at it, I kind of envision this podcast being something that’s like short, sharp, straight to the point. Not always, I often do reference research a lot, but if we can get away without referencing it … But we just have it in there just so if somebody tries to fact check us, they can look at it and blah, blah, blah. It is in the show notes, so you can have a look at that too.

Just the same as the next thing I’m going to talk about, which is low intake of B vitamins in general. So we’ve specifically spoken about B12 deficiency, that’s easily the most common one that is the most relevant. That’s at about 20% of the population above the age of 60 having a B12 deficiency is crazy. It’s such a potential easy win for a large percentage of people, but other B vitamin deficiencies are a bit more rare, but they definitely are a cause of fatigue in certain people. And something that I’m not going to try and back this up with strong research or anything like that, but anecdotally, a lot of people find even if they’re not deficient, if they increase their B vitamin intake, they often notice improvements in how they feel. But that’s a huge topic.

So I’m going to stick to the stuff that we definitely know for sure in terms of the deficiencies. B vitamins are found in a wide variety of foods. The easiest way to avoid deficiency in any of these individual B vitamins is to simply consume a decent or a good diet with a sufficient amount of a wide variety of foods. This will sort pretty much everything out without much planning, but then you’d be wondering the question, who does get these deficiencies then? If they are something that is worth us bringing up. It’s usually people who avoid specific foods, or food groups, or have less access to certain foods who might be more likely to be experiencing these issues.

There are plenty of famous examples of people, particularly like during war times and stuff like that, who only had access to certain foods and they experienced these deficiencies. Like one of them is called beriberi, for example, which results in a bunch of bad things basically. And fatigue is one of those things, but if you’re having a wide variety of foods, it’s unlikely to happen if you’re just the general person who is wanting to get the potential benefits in addition to just the bare minimum. Once again, it does come back to just having an overall good diet and increasing intake of these things.


So overall, from a nutrition perspective, if you are feeling fatigued, my first port of call would be to go get a blood test check to see where your iron is at, B12, vitamin D, and thyroid function. It’s easy to go get a blood test and that can all be done in the one test. So go check that, see if that’s all sitting where it needs to be. If that’s not the case, or if you want to check in addition to that, you could evaluate your energy availability. Particularly if you are an athlete with a high training load, or you’ve gone through dieting efforts, that might be an issue there.

You can consider your body fat percentage, like if you are on the leaner side, have you gone too lean? Is that a contributing factor to your fatigue? And then, just overall looking at the quality of your diet. So not only from the B vitamin aspect, but also just meal timing across the day, et cetera, might be playing some role in fatigue like carbohydrates, for example. So looking at … Yeah, overall quality of diet can also be a helpful one.


There are heaps of potential causes, but those ones would easily be the first ones I look at.

This has been episode 89 of The Ideal Nutrition Podcast. Thank you to everybody who’s listened. And as always, if you could please leave a rating and a review if you haven’t already, that would be greatly appreciated.