Aidan:
Hello and welcome to episode 196 of the Ideal Nutrition podcast. My name is Aidan Muir and I’m here with my co-host, Leah Higl. And today we’re going to be talking about whether fat burners work. And the general view in the evidence-based community is that they don’t work. But I to go a little bit deeper than that and look at both the mechanisms and outcomes. Something that kind of prompted this was like a few months ago, I don’t know, I was speaking with Tyler from our team and he was talking about how like he’s always viewed them as stuff that like doesn’t work, because that’s just whatever else says.
And then he looked at like some of the research in terms of like increasing energy expenditure. And it’s like, some of this stuff is actually like meaningful and like at least worth like thinking about a little bit more than just like completely dismissing. So we’re gonna talk about some mechanisms and also we’re look at some outcomes. So hopefully it’s just a little bit more interesting than just saying they don’t work.
Leah:
They don’t work. End of podcast.
Aidan:
That was 56 minutes. Second, sorry. Second.
Leah:
That would be a problem if that took us 56 minutes.
But just going through some mechanisms as to why they could potentially work is one, increased metabolic rate or energy expenditure. So generally helping with an increase in calorie output. They could also reduce your appetite. So make appetite management a little easier, decrease the amount of food you’re consuming. So having an impact on that side of the equation. They could potentially increase things like fat oxidation. But as we know, fat oxidation doesn’t necessarily mean fat loss. Obviously we do also need a calorie deficit there, but that is one of the potential ways in which they could assist with fat loss. And then we also have another mechanism of potential better muscle preservation and therefore more fat loss in the same circumstances.
Aidan:
I’m going to go through one by one with each of those mechanisms. So the first one is the reduced appetite is obviously relevant. That makes sense. I have spoken previously though about how a lot of the tools that help with appetite management often have a bit of a finite lifespan and it kind of becomes a new normal. The simplest kind of explanation I’ve got for that logic is being in a calorie deficit over time typically makes you hungrier and increases your desire to eat if you are sticking in a deficit.
Therefore, if you kind of use any tool to kind of achieve that, eventually your body just sends stronger signals. That’s my own two cents, my thoughts on that, but it’s part of why a lot of the time we won’t see something that reduces appetite outside of medications or surgery having kind of a lasting impact. The next one is the increase in energy expenditure.
Obviously that can make it easier to stay in a deficit if you have an increased energy expenditure. That is another relevant point. But it’s very much worth noting that overtime appetite often does adjust to match that as well. Using an extreme example, most people have probably heard of somebody who has gained weight while training for a marathon. And it’s just like this extreme energy expenditure has just made them so hungry. Or if not using that extreme example, there’s just a lot of athletes who are just hungry people because they do a lot of training and stuff like that. So even in the increased energy expenditure could be offset if appetite went up in line with that, which is a very common thing.
Increased fat oxidation sounds promising, but as you said, Leah, like we know that there is a difference between fat burning and fat loss. When you go deep down to rabbit hole, you see in the majority of cases that this just doesn’t matter. Using another extreme, let’s pretend you quote on quote hack the system and you found a way to massively push everything towards burning fat instead of burning carbs/glycogen.
If you’re still taking in anything that converts to glycogen in the body, so glycogen is a storage form of glucose and either carbs could be stored as glycogen or protein can be stored as glycogen. And I hope everyone’s eating both, but like I hope surely you’re at least focusing on protein. If you hack the system to the point that you’re like exclusively, I know this is an extreme example, but exclusively burning fat and you’re never burning glycogen, eventually your glycogen stores would have to max out. And then what happens once you consume, once you have more glycogen beyond what your max capacity is, it has to go somewhere.
It would get stored as body fat. It’s just that the body is a bit smarter than that. It would never actually let you hack the system to the point that you’re maxing it out that way. These mechanisms would happen earlier. And that’s part of why you often see these things balancing out. Even if you didn’t trust me that, you can just look at outcomes. Like you can do that and you would find that the conclusion is the same, but that’s just part of my explanation.
And then obviously better muscle preservation would obviously help, but I don’t really see many fat burners even making that claim to be honest. And the ingredients just don’t really like line up with that, but we can talk about that as well.
Leah:
So now that we’ve covered for more of a mechanistic point of view, let’s actually look at the individual ingredients that could be in some of these fat burners. So the most common one that’s in majority of fat burners is going to be your caffeine, which can increase energy expenditure, suppress appetite and may increase fat oxidation. So this is why it’s often in these fat burning supplements. One example of this is a study where 90 milligrams of caffeine was taken and compared to a placebo daily for two weeks. And that led to 25 calories extra burn per day. So obviously, yes, there was an increase in caloric burn, but when we’re considering how much 25 calories is in the context of our overall total daily energy expenditure,
It’s not a huge shift. The next one you may see in some of these supplements is L-Carnitine. And technically this can be used in the body for fat transportation, but supplementing it doesn’t seem to make much of a difference. So one of the major reasons is that the absorption of this supplement is quite poor when it’s consumed orally. But even if we look at the outcomes, if we’re looking at studies with, where people are orally consuming L-Carnitine, it doesn’t really show much of a significant difference in regards to fat loss.
Anyway, another one is green tea extract. So this is in a lot of like, what’s that X50 or something like that? That’s the big green tea extract one. OxyShred, pretty sure that contains green tea extract. So this has the very similar mechanisms related to promoting fat oxidation. But once again, outcomes haven’t been very promising in research for fat loss specifically. One of the last ones I’m going to touch on is capsaicin. And this is often added to increase metabolic rate through the thermic effect. And it can also have a small appetite suppressing effect as well. This increase in calorie expenditure is documented in some of the research as being around 50 to 75 calories per day if higher dosages are used.
Which is like, okay, now we’re getting to something like almost a hundred calories a day. Like that can be somewhat actually meaningful, especially if you’re combining it with the caffeine. But there are some risks here in terms of like maybe some GI upset when you are taking quite a large amount. And once again, how that plays out in like the longer term perspective from a fat loss point of view, maybe not super significant in that way. We could definitely keep going through tons of different ingredients that are put into these supplements and we’d be here all day. But those are the main ones you’re going to come across.
Aidan:
Yeah. And I think that big increase, big is debatable, but like the increase of capsaicin of like that 50 to 75 is a great example of the kind of thing that Tyler was pointing to just being like, I think some people overlook this being like, do a multi ingredient thing. Maybe you do get the a hundred calorie difference. But somebody, obviously would scale based on size, but like for somebody who struggles to create a decent sized deficit, that could be something that helps a little bit. And I think the very valid point is it’s like, well, you just having a drink. You’d like, it’s not actually a lot of effort to get that small win. If you wanted that win is a bit of an argument. I do think timeframes really matters though, where I do lean towards this stuff matters a lot more over the short term than it does over the long term. But you could also make the counter argument. like, well, both of us agree that you probably shouldn’t be striving for a deficit or fat loss all the time. You probably should be doing it in a phase anyway, but let’s now look at outcomes. And the only one I’m going to talk about is that longer timeframe because that’s what I really care about. And I think that’s a fairer way of kind of assessing that.
So looking at a 2021 meta analysis, looking at all of the research on fat burners at that time, that went for over eight weeks in duration. You basically found no difference between fat burners and placebo. Once again, that’s kind of why the evidence-based community has kind of been like, ah, this isn’t really doing anything because it’s like, you take this consistently for eight weeks and you find no difference in fat loss on average. It’s a pretty clear piece of evidence that either they do nothing or the difference is so small that it’s not really worth looking at, particularly when you factor in that oftentimes you have to go so high in caffeine in some of these supplements.
That’s like unless you specifically wanted to go that high in caffeine for other reasons, there could be downsides in doing that. And just looking at that eight weeks, it just kind of matters for like once you’re above that, the appetite stuff that I started talking about how that kind of balances out the energy expenditure, how it’s like your appetite kind of increases in proportion to an increase in energy expenditure. I just think once you get past eight weeks, definitely past 12 weeks, that stuff is really balanced out by that point, which wouldn’t really show up over a short and shorter duration.
Leah:
So what’s our overall interpretation of this space? I think we realistically come to the point that many dietitians do and that’s fat burners either have no effect or if they do have an effect, it’s gonna be quite a small one. And in the cases of the small effect, you start questioning like, is it worth it?
Like would it be worth taking a noticeably different intake of caffeine than what you would normally do just for the increase in like very small increase in energy expenditure? Maybe not. Maybe there’s too many downsides for that. A lot of these fat burners are also quite expensive. So financially, does it make sense? Could you be putting that elsewhere in your journey that could make things a little easier? Possibly. So it’s not necessarily something that I would go out of my way to recommend to my clients, but if a client is taking it and likes it,
I’m also not going to be like, no, don’t do that.
Aidan:
Something that has shifted my perspective a lot over the last few years is that get a lot of free supplements. I get a lot of, I never do paid partnerships with anybody, but if somebody says to me, Hey, we’re going to send you this supplement. Would you accept it? Like, sure. Like maybe I’ll put it on my story. Maybe I won’t, but like, I won’t do anything beyond that. And I don’t promise there’s no strings attached. So I do accept some free supplements and it’s shifted my perspective a little bit on how I view whether a supplement is good or worth taking or whatever, because it takes the money component out of it.
I’m going to use an example. I recently got given creatine gummies. I personally probably wouldn’t pay for it because I have no issues taking creatine. It’s really cheap in powdered form. It’s really easy for me personally to consume. Somebody sends me free creatine gummies. I’m taking them.
Leah:
Yeah. Why wouldn’t you?
Aidan:
I’ve had a few supplements like that. Like I have a sleep supplement every night. I sleep well regardless, but like if it’s there, I’m going to take it. Like, so, but I wouldn’t pay heaps of money for it personally right now. So that’s just my perspective, but it makes it even clearer to me if there’s something I wouldn’t take, even if it was free using two examples, athletic greens, shout out athlete greens. Just don’t like the taste of it. Not having it for free.
Bit of a name in shame, but the other one though is like a fat burner. If somebody sent me a fat burner, I wouldn’t take it for free. And it’s partly related to that kind of caffeine thing. Just like I have a good amount of caffeine each day that works really good for me and I don’t want to mess with that. Like I just, I will just do that. If I was going to have a supplement that contained caffeine and fit perfectly into that amount that I feel greater, maybe, but like, I don’t know. I wouldn’t take a fat burner for free, which is part of why I’m like, it’s not something that I’d really recommend to anybody ever.
Leah:
Good summary. This has been episode 196 of the Ideal Nutrition Podcast. If you haven’t yet left a rating or review, it’s always greatly appreciated for you to do so, but otherwise, thank you for tuning in.