What's That Rash? - Should you exercise on an empty stomach?

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0:33on ABC Radio National and ABC Listen. So I have two questions for you, Norman, today. Two? Yes. I find one hard enough. I live to challenge you. So the first question is, what time of day do you typically exercise? And my second question is, do you normally eat beforehand or not? So let me answer the second one first, because I'm much more interested in what I eat before I broadcast. Oh, you have this weird, have you brushed your teeth? This is a thing for you, isn't it?

1:02I brush my teeth, but I'm actually, I haven't had something to eat, and my tummy is grumbling right now. I can't hear it. I'm much more obsessed with that. So I, yeah, I cycle to work, so that's a bit of exercise. Go to the gym whenever I can, usually in the morning, but sometimes in the afternoon. And do I exercise on an empty stomach? Well, sometimes I do, but not consistently.

1:27Well, okay, well, let's get into the evidence for and against this today on What's That Rash? Which is the show where we answer the health questions that everyone's asking. Well, today we have Grant and Janet basically asking us the same question but in different directions, which is basically about should I exercise on an empty stomach or not? Grant says...

1:50My question is slightly adjacent to an earlier episode about the best time of day to exercise. I am definitely a morning exercise person. If I'm trying to lose a bit of weight, does it matter whether I eat breakfast before or after I exercise? And Janet says, I am definitely not.

2:09A morning person, I have no desire for food before my exercise sessions, but I'm wondering if this is a good decision. I see an exercise physio every Tuesday and Thursday morning at 8 a.m. Somewhere along the way, I heard that exercise on an empty stomach would mean my body would burn its fat stores. However, my N equals one experience in the last eight years would suggest otherwise. What does the evidence say about eating before exercise for a slightly squishy middle-aged woman?

2:38self done. Come on. I'm sure you're not that squishy. You just feel squishy, maybe. I'm thinking Janet is going to see an exercise physio twice a week for eight years. You're probably lapping most of Australia right now, Janet. So don't, yeah, like you say, Norman, go easy on yourself. But it's a great question. This idea about time of day when you're exercising. If you exercise in the morning, you don't want to be working hard on it and empty stomach, but do you need some fuel for the fire? And this question about fat loss, which is what a lot of people are hoping for when they exercise. So let's get into it.

3:11And I think I know where Janet heard that story about burning body fat. It was probably on the health report. It was on the health report, our sister podcast. Like how long ago would she have heard that on the health report? Quite a few years ago. And I can remember it was the University of New South Wales were looking at fasting and they had people doing fairly extreme exercise on static bicycles and stationary bicycles and looking at fatty acid burning and show that it did burn fatty acids.

3:38And if you had green tea or black coffee afterwards before you ate anything, that increased the burn. But the question is, that's one study. Does it generalize beyond without giving away too much upfront? And it's one moment in time as well. I don't know what you're like, Norman, but if I do a high-intensity exercise session in the morning...

3:59I am insatiable for the rest of the day. I'm just like my body is like, come on, refuel me. And so whether I burnt more fat or protein or whatever during the exercise session is almost immaterial because my appetite makes up for it regardless later in the day. Off you go. So let's look at some of the research in this area.

4:19So we brought together, rather than just a single study from the University of New South Wales, good though that study might have been, we're trying to bring the evidence together to see what the sum total of the evidence is in this area. So when you balance it out, and a lot of this is about morning exercise. We'll come back to afternoon exercises in a minute.

4:39looking at morning exercise because there's a natural fast overnight and therefore you're in a fasting state if you like if you exercise in the morning before you've had breakfast or before you've eaten anything. Bottom line is on balance there is evidence that you burn more fat if you exercise on an empty stomach.

5:01And that's measured by what's called free fatty acids. So if you're burning fat, you tend to produce these short chain fatty acids that course through your bloodstream and could be measured. There's also a bit of evidence that it changes the way your muscles talk. And nobody's quite sure whether that's good or bad for your muscles. But it depends on the exercise. What are you doing when you're exercising?

5:29Exercise is a giant bucket, right? Like you could be getting up and doing a three hour cycle. You could be getting up and doing a one hour yoga class. You could be getting up and doing a weight session. And what your body needs from each of those things is very different. And also what you're hoping to get out of each of those sessions is really different. Exactly. So let's look at more extended aerobic exercise. And that's what you're doing in the morning after fasting or after having a good breakfast. Turns out that extended aerobic exercise, you do it much better, much less stressfully, if you like, if you've had breakfast. So breakfast is a good idea. When you say extended, you mean like more than an hour? More than an hour. So you're out for a long walk, a long jog, a long cycle, that sort of thing, or even a long session in the gym where you're doing mostly aerobic exercise. And as we've often said,

6:24and watch that rash. Muscle strengthening exercises are often quite aerobic as well. Just try doing squats with a set of weights. So, extended aerobic exercise, good to have had your breakfast, you will feel better doing it. So, shorter forms of exercise. Look, that's the balance of evidences that you do seem to burn fat. The question is, does that make any difference in the long run? And again, as you quite rightly said, Tegan, what's your goal here?

6:52Is your goal here to burn calories? Is your goal here to get fitter, be metabolically healthier? Is it to lose weight? What are your goals here? So let's go through these. Well, a lot of the reason why people exercise is fat loss, like we said, but a lot of the studies and a lot of the outcomes that people are often looking for are performance based. I want to run faster or further. I want to lift heavier. And for that, you do need fuel.

7:21Yeah, and that's related to athletes, so people who are at the elite end of the exercise spectrum and are trying to improve performance. For most of us, we're just happy if our weight is static or goes down a little bit or we build muscles. And when you look at the individual studies that these meta-analyses or systematic reviews are made up of, they're often very small studies. Oh, and short-term as well. Like we're talking 16 people.

7:48Six weeks, like small and short. And blokes. Ah, yes. So, blokes do seem to dominate. You know, Shelby, trainer, producer who... does a lot of research, in fact, all of the research for what's that rash, we just... Don't give away our secrets, Norman. We're just the cosmetic on top. There seem to be a lot of studies with 10 males or 12 males for some reason, which is hard to... Maybe that's the number of friends the researcher has. The researcher had. The other thing that stood out to me in this space specifically when we're talking about exercise science is most of the participants in studies seem to be athletes, rather than people like...

8:28Grant and Janet, who I'm sure are very athletic, but probably more representative of the Australian population than the sorts of people who are at AIS. Yes. So let's look at weight loss, for example. Some people believe if you don't have breakfast, you exercise. Well, you've just said it yourself. You're ravenous. You eat a lot during the day. Does that mean you actually put on weight? So paradoxically, you put on weight after about a fasting exercise. Well, there is a research looking at that and you don't.

8:57Really? Yeah. You may, I would refer to one of our earliest shows and what's that rash where we talked about whether or not you should have breakfast, whether you can skip breakfast safely. And the evidence is that maybe you lose a little bit of weight if you skip breakfast. The reality is that while you might refeed a bit after fasting based exercise, you don't refeed enough that you're going to put on weight. So it's not a cause of weight gain.

9:26What about your muscles? And here the evidence is just very confusing. There is some evidence from some studies that you get some benefit from your muscles from fasting-based exercise, but there's other studies that suggest that when you exercise fasting We haven't talked about what's going on in your body. You're burning your glycogen stores. So that's your glucose stored in your muscles. It's not glucose, it's glycogen, but it's the carbohydrates stored in your muscles. And you can burn through that quite quickly. And when you burn through that, that's when you start burning fat. But you don't just burn fat, you burn protein. So you're potentially losing muscle on your way through there too. That's the risk. You've got to be very careful about burning fat.

10:12because of this problem that you might lose muscle as well. Yeah, your body doesn't know what your fitness goals are. It's just out here trying to get you moving. It's just out here trying to answer the questions that you're asking at each morning. So let's get down to basics here. What's important is that you exercise. It doesn't really matter at our level when you exercise during the day. It's when you're able to exercise and do it consistently. And with fasting, In the end, it doesn't really matter whether you're fast or not. It's probably more important to be fed. There's a little bit of research which suggests that it's harder to exercise when you're fasting and some people feel demotivated during exercise in a fasted state and they feel better about their exercise if they've had something to eat. So let's actually talk about that specific study for a second because it's super interesting. In that one, the people who had fasted weren't exercising

11:08before or after breakfast. They're actually having a middle of the day fast. It's kind of an unusual fasting pattern. And they basically had breakfast, didn't eat.

11:19throughout what you would think of as being in the work day, and then sort of exercised at the evening and then they had their evening meal. They were trying to sort of tease out whether if you wanted to exercise in the evening, whether there was a benefit from fasting. But like you say, the outcome was basically people were like, I'm sad and hungry. I don't want to do an exercise. Please don't make me do this. And in terms of the metabolic effects, they're quite similar to fasting at breakfast that maybe is an increased fat burn.

11:45But it wasn't significant. Did it change your outcome that much? Probably not. So it really feels like a very familiar take home message. It's like the exercise that you do, that you can do consistently is the best exercise. The time of day that suits you to exercise consistently is the best time of day to exercise. And eating before or after exercise, whichever feels best for you and your body is probably, you're not giving yourself much of an edge either way. If you're forcing yourself to eat before exercise or withholding food before exercise. Janet and Grant both basically were like, this is what works for me. Is that okay? And the answer kind of is yes. Yes. And the one provisor there that seems to be fairly consistent in the studies is what we said right at the beginning is that if you're going for a boat of prolonged aerobic exercise, you're actually better off eating. Do you have a preferred pre-workout snack, Norman? Yes.

12:43I was just thinking about that this morning. I don't carb load, I yogurt and berry load. Nothing wrong with yogurt and berry loading. I personally have found my most reliable performance enhancing pre-workout in the morning is black coffee and half a banana, which I think I actually read somewhere like, you know...

13:03women's health magazine or something like that, but truly a reliable peer-review journal. My personal N equals one is if I want to climb hard, especially if I'm wanting to sort of feel powerful at the gym, have an explosive power, that is the thing that gets me there without kind of making me feel too blobby and heavy and like my body is doing too much work digesting.

13:27power. It's funny you should say that because there is some research that suggests that eating first does give you more explosive power and explosive power. Maybe something we'll look at in the future, what's that rash? So Grant's question specifically was if I exercise in the morning, does it matter if I eat before or after exercise? It doesn't sound like it really matters, but maybe we could talk about what to eat after exercise especially to sort of help your body recover.

13:51So the key here is to eat complex carbohydrates, not too much fat, certainly not too much saturated fat. So the traditional English or Irish breakfast is probably not for you, Grant. Exercise doesn't get you out of jail in terms of your coronary arteries. So you want something like, you know, my favorite yogurt and berries and a cup of coffee. Norman Swan brought to you by Big Yogurt.

14:16I go for a small yogurt. Big yogurt with a big B and a big Y is you're in the pocket of big yogurt. What about protein? Protein is really important, and it depends on whether you're muscle building. And we actually have an episode on protein, which gives you an idea about that. Again, the information about when you should take your protein and how much is confusing. But you should certainly have some protein at breakfast after exercise, assuming if you're having an after exercise, so there's protein in your body.

14:44when you might be in a state of muscle building. That's the only thing that quietens my hunger ravenousness after morning exercise, actually. That quietens your beating heart. Not too quiet. I don't want my beating heart to be too quiet. If you have a tried and tested pre-workout snacko, tell us what it is, that rash at abc.net.au. That's our email address for all of your what's that rash needs. Bottom line though, Norman, to Grant and Janet. Eat or not eat, depending on what your preference is.

15:12the outcome is going to be the same. Just be a bit careful if you're going for a prolonged exercise. So don't worry about it. You do, you boo. Well, Grant and Janet, happy gymming. And let us know how you go. If you have a question you want us to tackle that rush at abc.net.au is our email address as previously said. What's in the mailbag?

15:31So a bit of mail about hypnotherapy. Nikki has messaged in to say, so glad to hear your episode on hypnotherapy. Here's my experience with it. When I was 15, my English teacher made us all a tape with revision for our O levels on it. Nikki's clearly from the UK saying he was a qualified hypnotherapist and told us to play it when we went to sleep at night on our cassette players.

15:55We all passed and I can quote a ridiculous amount of Shakespeare still that I had never learned on purpose. Nikki also tried hypnotherapy for weight loss in her late 40s. After I had a particular session with a professional hypnotherapist, I went to buy bread on the way home and the lady in the bakery asked if I wanted anything else. And I found myself saying, oh no, thanks. I don't eat sweet stuff and thinking to myself.

16:20What did I just say? I really wanted a bun, but it worked out as I walked out without any sugary bun because I was too embarrassed to contradict myself. Nikki's third hypnotherapy anecdote. Oh, she's a major consumer of hypnotherapy. So Nikki goes on to say.

16:36Finally, after I had a spinal fusion two years ago, a very nasty but fortunately successful operation. On day three after the nerve block wore off, I was in terrible pain. In my despair, I googled hypnotherapy sleep pain. Lo and behold, a YouTube site came up and I managed to get 45 minutes of sleep. I used it for many nights until it came good.

16:59I found it fantastic. So pleased to hear all that, Nikki. Well done. Is that an n equals one or an n equals three? I think it's one over three. One over three. Nikki, thank you so much for your stories. Plural, if you have a story you want to tell us about something you've heard on WhatsApp Rash, just email us. That rash at abc.net.au. See you next week. See you then.