Jonathan Steedman (00:01.208)

Hey food groupies, we're gonna talk about smart devices, smart watches, fitness trackers, Fitbits, garments, my personal favorite, the Apple watch. well, not just because I'm an Apple fan boy, honestly, this thing changed my life. It's been so amazing. But anyway, that's not what we're here to discuss. We're here to discuss smart devices, fitness trackers, ability to measure and accurately report on

particularly calorie burn, calorie expenditure, energy burn, energy expenditure. Okay? It's a topic I get asked about a lot because it is something that comes up a lot. I know that a lot of people use this data and are interested in this data. So I wanted to give you some context around this data so you can interpret it properly, figure out what you should be using, figure out what data is maybe not something that you should be putting too much stock in.

and going from there. again, a bunch of studies in the show notes as well, not as always, but if the topic is need studies, this one does. So there's a bunch there if you want to go look through them directly. I will say that the latest one I could find on this sort of stuff was from 2020. I completely understand that technology moves pretty quickly. I wouldn't be surprised at all if in a few years time, three to five, whatever years, this podcast is wrong or no longer relevant because

Maybe the smart watches and smart devices have gotten much better at tracking calories. I've also just given up the game there, haven't I? You know where I'm going with this. I'm so bad at this. Anyway, well, there you go. You don't have to keep listening. They're bad at tracking calories. The end, I'll talk to you later. No. So, yeah, all of the claims I'm about to make are from current slash slightly older data. If you're listening to this in the future and you're like, but.

All of this new data has said that these watches are accurate. It's probably because the Apple series 14 watch is more accurate than the Apple series. I don't know what I've got, something. Anyway, cool. Overarchingly, the biggest issue with calorie tracking is, sorry, I don't mean like fitness power calorie tracking. mean like reporting on your energy expenditure. There's just, it's really,

Jonathan Steedman (02:23.423)

inconsistent. So all of the studies that compare the measurements, the calories measured, the calorie expenditure measured by a smart device, and compare that to a gold standard like indirect calorimetry, or something called doubly labeled water, these are these are very validated, what we call the gold standard of testing energy expenditure, that's what we would compare everything back to. And the differences between what the smartwatch

or device reports compared to the gold standard reports is just so broad and can be so varied that it's just, it's not helpful. Okay, if the error range, if the range was smaller, maybe we could start to use that data, but it's so broad, it's at the point where it's like, I feel like they're just guessing still, basically. It's just a shot in the dark. And for something like calorie expenditure, the way that people use it,

they treat it like it's really accurate. A lot of people use it to inform exactly how much they're going to eat in a day, right? So if your watch told you, burnt two and a half thousand calories today, I'm gonna eat two and a half thousand calories. And it could be that actually you should have eaten three or actually you should have eaten two thousand. But you've eaten two and a half thousand which could be kind of not helpful.

because you kind of trusted that watch a little bit too much. So overarchingly, I would say do not take the absolute value that the watch reports on very seriously. I think the relative value, IE if you're comparing what you burnt in yesterday's session to today's session and today's session was much higher, very high likelihood that that session was more intense and you did burn more calories. Now, if it's 200 more calories, that's what you don't know. Maybe it was 200, maybe it was 400, maybe it was 100, but

there was probably an increase. So you could use it for that sort of thing if you wanted to. My understanding is heart rate is getting pretty good as is step count is pretty solid for most of them. And for a lot of people that can be really helpful if you're trying to do some zone two training or the rage at the moment. For good reason, by the way, I'm not besmirching that, but if you're trying to do some heart rate zone training, using a smart device for that could be helpful.

Jonathan Steedman (04:46.132)

If you are someone that tracks steps and you are trying to increase your movement and you do find that having a baseline measured of X amount of steps and wanting to increase that is helpful, a smart device is really, really good for that as well. I just want the take home message to be, don't pay much attention to the absolute calorie value and certainly don't use it to influence your food intake. If you...

are then thinking, well, then how do I know, Jono, surely I do need to eat more if I'm training. Yeah, you do, but a good calorie calculator, you punch in all your details, will take your physical activity levels slash your exercise levels into account and it will factor that into the number that it spits out. So unless you're doing what's called like an RMR or a BMR calculation, which is your baseline or basal metabolic rate, which not too many people do when you jump online and you...

do a calorie calculator, it's typically a TDEE, a total daily energy expenditure calculator. And that will take in all of the other factors into account. You don't need to add watch data to that. Adding watch data to that, like I said, is actually just gonna make it less accurate. So in summary, I love my smartwatch. It's amazing. But so many other things. I don't really use it for much exercise data, other than like running, run times, split times, that sort of stuff.

occasional heart rate stuff, even that I don't really care about to be perfectly honest for my purposes. But I certainly don't look at how much, how many calories it's told me I've burnt. Sometimes I do cause it's fun, but I certainly don't use that data to inform any of my decisions around my eating or my training. And you shouldn't either. All right, hope that helped. I'll chat to you next time.