Blood sugar is one of the rare nutrition topics where everyone agrees: We should avoid big peaks and dips and aim for a steady curve.
Spikes cause inflammation, accelerate aging, and lead to type 2 diabetes. Crashes make us feel moody and tired, and crave foods we don’t need.
We can control our blood sugar through what and how we eat. But something else affects it — physical activity.
Exercise has a profound effect on your blood sugar response. Together with your food choices, being physically active helps keep your blood sugar level even.
In this episode of ZOE Science & Nutrition, Jonathan speaks with Javier Gonzalez and Sarah Berry to find out how exercise affects our blood sugar response — even when we’re fasting — and how much exercise we need to do to benefit.
Javier Gonzalez is an associate professor of human physiology at the University of Bath whose research focuses on the interaction between diet and exercise.
Sarah Berry is one of the world's leading experts on human nutrition. She has personally run over 20 randomized clinical trials looking at how humans respond to different fats.
If you want to uncover the right foods for your body, head to joinZOE.com/podcast and get 10% off your personalized nutrition program.
Episode transcripts are available here.
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[00:00:00] Jonathan Wolf: Welcome to ZOE Science & Nutrition, where world-leading scientists explain how their research can improve your health.
Blood sugar. It's one of the rare areas in nutrition where everyone agrees we should avoid big peaks and dips. Repeated spikes can cause inflammation, accelerate aging and increase our risk of type two diabetes. Blood sugar crashes can make us feel moody and tired and even make us hungrier. We can control our blood sugar through what and how we eat, but there's something else affecting our blood sugar. Physical activity.
Exercise has a profound effect on our blood sugar response and could help us maintain better control of our blood sugar for a healthier life. Today I'm joined by Dr. Javier Gonzalez, associate professor of human physiology at the University of Bath, whose research focuses on understanding the interaction between diet and exercise.
I'm also joined by nutritional scientists and ZOE regular Sarah Berry. She's one of the world's leading researchers into how food affects our blood sugar. Sarah says she has a vested interest in today's topic as 2023 is the year Sarah plans to start exercising regularly. In this episode, we find out how exercise affects our blood sugar response, how much exercise we need to benefit from, and the surprising effect exercise may have on our blood sugar even while fasting.
Javier and Sarah, thank you so much for joining me today. Why don't we start, as we always do with a quickfire round of questions from our listeners, and the rules are the same as always, please, a yes, a no, or you if you absolutely have to a one sentence answer, but no more than one sentence, which we always know is difficult for a scientist, Javier.
Are you ready to go?
[00:02:03] Javier Gonzalez: Yes.
[00:02:04] Sarah Berry: Yes!
[00:02:05] Jonathan Wolf: Brilliant. Alright, starting with Javier. Can exercising improve my blood sugar control?
[00:02:12] Javier Gonzalez: Yes.
[00:02:13] Jonathan Wolf: Is it common to have a blood sugar crash after exercising?
[00:02:17] Javier Gonzalez: No.
[00:02:18] Jonathan Wolf: If I exercise before breakfast, will that put too much stress on my body and potentially cause inflammation?
[00:02:25] Javier Gonzalez: No.
[00:02:26] Jonathan Wolf: Should I, therefore, exercise before breakfast?
[00:02:28] Javier Gonzalez: It depends.
[00:02:31] Jonathan Wolf: You are allowed that sometimes. I know this is a tricky one. If you could see Javier, you can see him sweating with like, you're asking me to make this so simple. This just doesn't seem right.
All right. Can exercise affect fats in your blood like cholesterol?
[00:02:44] Javier Gonzalez: Yes.
[00:02:45] Jonathan Wolf: All right. And Sarah, one for you.
Lots of snacks are sold as energy boosts to get us through the day. Do they help you with your blood sugar?
[00:02:52] Sarah Berry: It depends.
[00:02:54] Jonathan Wolf: So Javier, Jade on social wants to know if it's true that a 30-minute walk is as good as 30-minute cardio for menopausal women.
[00:03:03] Javier Gonzalez: Well, as always, it depends on a variety of factors. I'm assuming that with cardio, we're talking about more intense exercise, and on that basis, a 30-minute walk probably isn't as good as 30 minutes of cardio for overall health effects, especially as we are aging. We need to maintain muscle mass. We need to try and maintain our bone health as well. And that's where more vigorous intensity exercise can really provide a benefit. But having said that, 30 minutes of walking has a whole load of health benefits, especially for things like blood sugar control, which we can get into later on.
[00:03:38] Jonathan Wolf: Brilliant. Well, why don't we get into all of that And you know, what I suggest is maybe we could just start with what is blood sugar and why should we care about it.
[00:03:49] Javier Gonzalez: Yeah, so blood sugar is a main fuel providing, especially our brain with fuel throughout the day. And so when we are not eating, our brain is still using fuel and we need to provide it with that sugar in some form.
So, When we wake up in the morning, most of that sugar is coming from our liver. Our liver is breaking down its stores of sugar and it's also producing sugar as well. Providing the brain with that important fuel. And then with other types of activities that we do throughout the day, things like our muscles will also need some of that sugar as fuel.
[00:04:25] Jonathan Wolf: It sounds pretty obvious therefore, it's very important. We all know if your brain stops working, everything else happens. But there are so many different processes in our bodies, so why do we care about blood sugar particularly? What is it that makes it such a big focus of your study, for example?
[00:04:39] Javier Gonzalez: Yeah, it's probably because we need to keep our blood sugar within a relatively tight range to maintain health. Too low and our brain doesn't have enough fuel and we can end up going into a coma. Whereas if we have too much blood sugar, then that can cause damage to our blood vessels. So we need to keep it in a tight range. And for that reason, at least in most healthy people, we have a load of physiological processes that aim to keep that blood sugar within that tight range.
[00:05:09] Jonathan Wolf: And maybe you could actually talk through that. Maybe imagine like, you know, I wake up in the morning or maybe even before I wake up. Can you just talk me through what happens during a typical day in terms of this sort of blood sugar control you're talking about?
[00:05:21] Javier Gonzalez: Yeah. When you wake up, first thing in the morning, you haven't had anything to eat for probably 10 to 12 hours. Your brain is still using glucose and at that time you've probably got about five grams of sugar in your blood. Your brain is using about that amount per hour and other tissues are using sugar up as well.
So if you weren't producing any sugar, you'd run out of sugar in your bloodstream, certainly within an hour, probably within about 30 minutes. And so what happens is our liver is, breaking down this stored sugar, releasing it into the bloodstream to provide that sugar for the brain and the other tissues.
And it's also producing sugar from things like proteins and other sources. That's when you haven't eaten. The next thing you might do in the day maybe has some breakfast. So that breakfast might have carbohydrates in it. And so now we've got sugar appearing from our intestine as we've digested and absorbed that carbohydrate. Now we've got an extra source of sugar in the bloodstream, and now the challenge is actually preventing the sugar from rising too high.
So one of the first things to happen is that we'll release a hormone called insulin and that insulin will cause our liver and our muscle to respond, to try to buffer the glucose, the blood sugar so it doesn't rise too high. So what happens with the liver is that it goes from producing glucose to starting to store glucose.
And the muscle also starts to take up sugar out of the bloodstream. It does it slightly more slowly than the liver at first, but then it speeds up, and actually, quite a lot of the sugar from the meal that you eat will end up in your muscle stored as something called glycogen in the storage form of sugar.
[00:07:08] Jonathan Wolf: And Javier I want to stop there for a minute, just because this is a complicated picture that you are describing, and I know you're simplifying it for us, but you're already describing like how much is going on in our body, right? I just thought I woke up, like walked downstairs, didn't go into a coma, which I normally, you know, have never thought about that as a success, but I can now see, you know, every half hour if I don't go into a coma, my body's doing a great job. There's a lot that's going on here, isn't there? In, order just to make sure you've got this regular amount of sugar in your body. Why is food such an important part of this story and why do people worry so much and talk so much about blood sugar?
Because you might say, hey, yeah, there's also all sorts of clever things going on inside my brain or whatever, but we never think or talk about them like, what is going on here that causes us to, you know, you to want to study it and us to really think about this being important for how we might choose to behave.
[00:08:02] Javier Gonzalez: Yeah. There are probably two main reasons why it's important to understand blood sugar. One is that it gives insight into our health. So if we compare people's responses to the same meal, The different blood sugar responses can tell us are their muscles working well. Is their liver working well?
And then secondly, food has a direct impact on our blood sugar levels. So a meal that has a lot of carbohydrates in it, particularly carbohydrates that are rapidly digested. We'll have a big increase, a big impact on our blood sugar level.
[00:08:36] Jonathan Wolf: And Javier, just to make sure everyone follows this, this is because basically your body takes those carbohydrates, which might be like bread or pasta or rice, and it's actually turning it into blood sugar, right?
[00:08:47] Javier Gonzalez: Exactly. Yeah. When we eat a meal containing any form of carbohydrate, it will ultimately get broken down and converted into glucose if it's not glucose already, which is essentially sugar, and appears in our blood as sugar.
[00:09:01] Jonathan Wolf: And Javier, I think lots of people are listening to this and saying, okay, this is all very complicated.
But I think the thing that you said that they're gonna be listening to is what really matters is how well do I control this? So I think you're saying, you know, if I can manage to keep this in a sort of fairly tightly controlled band, then everything is good. And they're probably saying, well, so what happens if I can't?
And why is that? So I think we had a lot of questions from people saying, you know, does my ability to control my blood sugar change with my age? With menopause? What's the reality of this?
[00:09:36] Javier Gonzalez: Yeah, so it certainly does change over our lifespan. And one of the main terms that people might hear is something called insulin sensitivity.
So that is basically how well our body is responding to that hormone insulin, which is the key hormone for keeping our blood sugar under control. And there are two key phases in our life where we all become slightly more insulin resistant, less sensitive to that hormone insulin. And that's in adolescence and also throughout menopause.
And all of us as we age will tend to become less insulin sensitive. In adolescence, it's largely because of the growth hormone that you get in as you're growing in adolescence that can reduce your insulin sensitivity. It's a normal process of adolescence. As we go through menopause. Then the hormonal changes there can also reduce our insulin sensitivity.
So they might be key periods of our life where we might pay particular attention to blood sugar control, but all of us, as we age, should probably pay more attention also.
[00:10:43] Sarah Berry: And Javier, we've got some great research from, ZOE PREDICT studies on the blood sugar changes that happen between males and females, as we age, and also whether you are pre, peri, or post-menopause, which fits in with exactly what you're saying.
So what we see is that at most stages, men have the worst blood sugar response to a standard meal compared to females. Then, females, we hit menopause, and bang it goes up to the level of men and actually worse than the level of men. And we actually published some research on this recently where we also were able to look at postmenopausal women and match them according to age.
So we could have a look if you are postmenopausal or premenopausal, but of a similar age, do you still have a worse blood sugar response if you're postmenopausal compared to someone of a similar age who is premenopausal? So that's taking away the impact of age and only looking at the impact of estrogen.
And we still saw a really big difference in people's blood sugar control with those that were postmenopausal, having far worse blood sugar control. So higher blood sugar responses to a standard meal compared to the premenopausal.
[00:12:00] Jonathan Wolf: Sarah has depressed us with the arrow of time and the...
[00:12:04] Sarah Berry: You're ok! Look, you're not a 45-year-old woman that's about to see that big spike soon, Jonathan.
[00:12:12] Jonathan Wolf: That's true. I'm already over a 45-year-old man who's been worse than you throughout my life to this point and has one of the worst blood sugar controls of anyone we've measured. But I appreciate that and I agree.
Where I was thinking of going with this though, Javier, is like your big area of research is actually all about exercise and how this fits with blood sugar, and I think that's exciting because it's talking about things that you can do rather than just what happens to us as we age. Could you explain at a high level so we can follow along hopefully, how exercise affects how our body is dealing with blood sugar?
[00:12:47] Javier Gonzalez: Yeah, and it's probably worth considering exercise in three main phases. So one is what happens to our blood sugars during exercise? What happens to our blood sugars immediately after exercise? And then what happens if we've done training? So if we've done months and months of exercise, how does that affect our body in a way that we can control our blood sugar levels? So if we start with the first one during exercise, when we start any form of exercise, our muscles are increasing the amount of energy that they're using. So they need the energy to continue the exercise. And a large amount of that energy will be coming from the sugar in the blood.
So the muscles will start taking up more sugar out of the bloodstream and so logically, you can immediately imagine that that's gonna help control our blood sugar levels. It's a slightly more complicated picture in that our liver will also start producing more sugar to try and provide more fuel to the muscle.
But if we do that bout of exercise after we've eaten a meal, then compared to just resting, it will tend to lower our blood sugar levels quite dramatically actually. So it's quite a potent effect. And actually, there's some really interesting recent research showing that really light intensity exercise, basically fidgeting and moving your knee up and down, they are calling it soleus press-ups, which is the muscle in our calves. Just if you imagine bobbing your knee up and down, doing that after eating a meal could drastically lower the blood sugar response by about 30% after a meal. So it can be quite a profound effect.
[00:14:29] Jonathan Wolf: By 30% just by fidgeting my knees around?
[00:14:32] Javier Gonzalez: Yeah.
[00:14:33] Sarah Berry: I always, unfortunately, eat my food whilst during zoom meetings, which is unfortunate for Jonathan, who's normally having to watch me munch away. And then I sit there feeling like, oh my gosh, I'm always telling everyone to go for a walk after you've eaten. But what you are telling me, Javier, is that I can just sit here and fidget, which is what I'm doing now, fidget my legs and that's gonna do the job?
Exactly. Well, I'm so glad I joined this podcast. That phenomenal.
[00:15:00] Jonathan Wolf: And I am a terrible fidget. So I know Javier, you've talked a bit about this to me previously and I have wondered if that is an important part of how I appear to always be so hungry.
[00:15:13] Sarah Berry: So if I was to go for a walk as we often recommend people to do after having their lunch, or I was to sit at my desk and fidget for however long, would that fidgeting have the same favorable effect in lowering my blood glucose response as me going on the walk? Forget the other aspects of the healthiness of going on the walk just for the blood glucose response.
[00:15:37] Javier Gonzalez: The walk is probably gonna have a larger effect because you've got more muscle groups that are being recruited during the walking, and studies have shown just two minutes of walking every 20 minutes throughout the day lowers your blood sugar levels by about 50%, whereas this fidgeting of the knee lowers it by about 30%. So it's hugely effective. But the more muscle groups that you activate, the more effective it seems to be.
[00:16:02] Sarah Berry: So basically every 20 minutes you either go to the toilet or get up from your desk and go make a cup of tea and you're onto a winner.
[00:16:10] Javier Gonzalez: Yeah. Yeah.
[00:16:12] Jonathan Wolf: And Javier, I think you said there was another level of exercise. You got the fidgeting, you've got going for walk. There's more beyond this?
[00:16:19] Javier Gonzalez: If you were to do, say a jog or a run and increase that intensity of exercise, then you get some other changes happening as well. So you start to use up the stores of carbohydrates in your muscle, and that will have effects that we can come onto after exercise, but it also produces an adrenaline response, so you get that adrenaline hit. And you can sometimes actually see an increase in blood sugar levels during exercise because of that adrenaline hit, it makes our liver produce more sugar for our muscles to use as fuel. So it's a normal response that people shouldn't necessarily be afraid of, but can be expected with high-intensity exercise.
[00:17:00] Jonathan Wolf: And actually I was going to ask a bit about the difference between what goes on in like a short burst of exercise. So let's say, you know, I just took my daughter to school this morning and I walked there and then I came back, and then I sat down in my chair versus something that's going on for longer.
Because you were talking about the way that there's only like a limited amount of sugar in my blood and even if I was eating some food, you know, there's only so much that's coming in, I guess every few minutes. So what happens in those two situations?
[00:17:29] Javier Gonzalez: Yeah, so with your kind of lower-intensity walking and that kind of thing, the muscle is mainly using up the sugars from the blood.
Whereas when you increase the intensity, it uses more of the fuels that are within the muscle itself, so it uses up its own carbohydrate store, and that will have more of an impact on your blood sugar after exercise than during the exercise.
[00:17:53] Jonathan Wolf: And so just to make sure that I've got this, your body actually has lots of different fuel tanks, so you know, if I think about this as like a car, we only have one place with a fuel. Now you've mentioned there's like little fuel, in our muscles but you also mentioned that our liver is like a big fuel tank because you talked about the way that that is providing blood sugar. And then also if I eat food, it's either rapidly or slowly sort of coming, you know, out of my gut and into my bloodstream. Are there even more, or is that -
[00:18:23] Javier Gonzalez: So the carbohydrates, the sugars that we have available are in those three main sources, as you say. Our muscles are actually where we store most of our sugar. We have, a smaller store in the liver, and then if we eat some sugars, then that's the third way we can get sugars available.
[00:18:40] Jonathan Wolf: Oh, that's brilliant. I'm doing the ZOE program right at the moment and as part of that, I'm doing an intermittent fast for the second week, which is a sort of study that we put on the top. So actually, so it's the first podcast I've ever done hungry, and I dunno if you can hear my stomach rumbling. I'm very bad at intermittent fasting, Sarah knows.
But it is interesting that you know, my blood sugar is basically completely flat, you know, from about sometimes like about two in the morning, it takes a while after dinner and then basically flat. And interestingly, it was still flat when I went on this walk, and then actually it has gone up a bit. Afterward, as I've come back, it's been snowing today, it was quite hard work pushing my daughter there and back again.
And so it's fascinating that all of that blood sugar is nothing to do with my food. You know, it's all to do with what's going on with I guess, these other systems.
Javier, can you talk me through this a bit, how does it stay so flat like this I've done a bit of exercise without fasting. You were saying before that might be a good thing or it might not?
What do I think about that?
[00:19:42] Sarah Berry: And Javier, to add to that as well would be great to understand a little bit about how some people, even when they haven't eaten food, have changes in their blood sugar. So you see a lot of people experience a small peak when they wake up in the morning in their blood sugar. So I wonder if you can add that to Jonathan's answer as well.
[00:20:04] Javier Gonzalez: Yeah, yeah, sure. So just starting with, Jonathan there, with if you were to fast then one of the main ways in which you are able to still maintain your blood sugar level in that healthy range is because your muscle will start to switch from using carbohydrates or sugars as the fuel to actually using fat as a fuel, so it's no longer needing to take up as much sugar out of the bloodstream.
The brain still needs to use sugars, but the liver is providing those sugars for the brain. And if you fast for a very long time, then your liver can actually produce a different fuel for the brain, known as ketones. But probably a separate topic.
[00:20:44] Jonathan Wolf: I definitely won't last that long. I'm miserable at fasting.
I'm hungry. As soon as this podcast is over, I'm going to eat a ridiculous amount of food and I see an enormous blood sugar spike because the whole point is you're not supposed to just squeeze breakfast and lunch into one meal, but I always do that, so I know what I'm going to do. I'm going to have like this enormous meal afterward, so my brain is all right, it can keep running on glucose Javier, as I think is the conclusion.
[00:21:09] Sarah Berry: Well, Jonathan's one of those rare adults. That really gets hangry. So any parents out there know what it's like when your kids are having too much of a fast, they get hangry. Having worked with Jonathan for many years, as wonderful as he is, he does suffer from serious cases of hanger.
I wouldn't have come on the podcast if I knew you were intermittent fasting, Jonathan, today.
[00:21:30] Jonathan Wolf: No, I think you're quite right. I apologize in advance to all the listeners for the fact that I'm clearly going to be in a worse mood than normal.
[00:21:37] Sarah Berry: You're being your normal, charming self.
[00:21:41] Javier Gonzalez: I'm completely the same as well. I do prefer to eat more frequently, but when you then did your walk and you see a spike in blood sugar after exercise perhaps, what might have been going on there is when you do the exercise, you get this adrenaline release and your liver is producing more sugar. Then you stop your exercise and your muscle no longer needs that extra sugar, but the liver takes a little bit of time to reset.
It's still producing that sugar, and so you can get a rise in the blood sugar level, and it's a similar thing that might happen when you first wake up in the morning, or it might also happen if you undergo a stressful situation. But you're not being physically active. So say doing a podcast when you're sitting still and you might feel a little bit nervous, then you can get a spike of adrenaline that might cause your liver to produce a bit more sugar than you actually need at that particular time.
And so you get a rise in your blood sugar level. And it might be one of the reasons why too much stress is a bad thing for our metabolic health.
[00:22:44] Jonathan Wolf: And while we're talking on this, I remember on our previous podcast where you're talking really primarily about exercise, you said that you've been doing this study where you'd said actually fasting and then doing exercise actually could be beneficial.
And I thought it sounded crazy, but I did wanna report back that I have tried it now. And I was terrified basically, that we're going to a gym session without any food and I would just fall over and it wouldn't work. And immensely to my surprise, it was completely fine. And actually, I guess this is back to your story about actually you've got all of these reserves in your muscles.
It was fine and I performed completely okay. And I'd always had this mind. I am someone who's proud of poor blood sugar control. I do tend to get these dips as we've discovered with our more recent research that actually, I was able to function. It worked. Because I was sort of thinking, but I wouldn't be able to do as well as if I had breakfast before because my mother definitely was, you know, you can't leave the house without having a proper breakfast, right? That was one of the iron rules in the house. I think my mother has generally been right over most things, so I was like, that must be true. But I finally found something where I think she was wrong because actually it worked and you know, Javier is nodding, saying this is sort of obvious, but I think most people aren't aware of this.
[00:24:02] Javier Gonzalez: Yeah, absolutely. And I'm glad you found some benefits. Certainly, our own research has been found, and we're getting onto that longer-term adaptation to exercise. So if you were to do your exercise regularly, then that can have some beneficial changes in your metabolism. That means we can better control our blood sugar levels.
And some of our research has shown that that improvement is even greater if you do your exercise regularly in that fasted state or just, just before having breakfast really. And a large part of that, we think is because the muscles themselves are adapting more to the exercise when you do it in that fasted state.
[00:24:43] Sarah Berry: And Javier, something that we're particularly interested in, as you know, ZOE is, personalization around how we might want to give one piece of advice to someone and different advice to someone else. And there's some work I think you've done in the past looking at how the timing of exercise in relation to the timing of food may impact your metabolic health. And if I remember correctly, you saw differences between males and females that might suggest we should recommend different timings based on that. I wonder if you could tell us a little bit about that work.
[00:25:18] Javier Gonzalez: Yeah, so the only study we've done specifically on meal timing and exercise for blood sugar control, was in a very small group of men.
So we do seem to think that at least in men, doing that exercise in a fasted state seems to have this benefit. In other work, we've done where we've looked at the differences in metabolism of men and women and of people of just a wide range of different demographics. We find huge differences in their ability to burn fat as fuel.
And so we link those two together because we think that our ability to use fat as fuel has some link with our ability to control our blood sugar levels. And so because we see large differences in people's ability to use fat as a fuel, we think there could be individual differences in the response to doing your exercise before or after breakfast.
Now the actual study on that, we've got ongoing at the moment to see do men or women benefit more from this type of exercise. So hopefully we'll have an answer in the next year or so. But for now, we speculate that there could be differences, but yeah, actively research it.
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[00:26:31] Jonathan Wolf: Amazing. We look forward to hearing.
Now, one of the things as you know, we really like to do on this podcast is make sure we can go from sort of this cutting-edge research to stuff that's actually actionable. And I think lots of people will be listening to this and saying, okay, so I understand therefore that exercise is a very important component of how I might be able to better control my blood sugar.
And some people may know that they really need to worry about that because, you know, maybe they've been told they have pre-diabetes or diabetes, or maybe they've done, you know, something like ZOE where they go, we've got this. I think what they want to know then Javier is, okay, help me to understand really, how often should I exercise?
How intensely do I need to exercise? And then actually we had lots of questions about specific types of exercise and I may come onto those, but maybe you could just sort of give some advice to help people to think about what they should do if this is something they'd really like to try and improve.
[00:27:27] Javier Gonzalez: Yeah. My overarching advice would be to do something that you enjoy and that you will do regularly. And there is probably an element of personalization here as well, where some people might enjoy certain forms of exercise and might even benefit from certain forms of exercise more than others.
And in a similar vein, I think the first point I'd make is, if you are only able to do low-intensity activity for whatever reason, then a good time to do that is after you've had a meal to lower that blood sugar level after each meal. And that's where low intensity, even the fidgeting that we discussed earlier, can have quite a profound impact.
[00:28:07] Jonathan Wolf: And Javier, just before we move off, just to help people understand like what is low-intensity exercise? I'm guessing fidgeting most of the time is probably a bit more than that. What could I be doing if I wanted to be doing that?
[00:28:17] Javier Gonzalez: Yeah, fidgeting, walking around, household chores count, gardening, anything like that where you are moving around but you're not really getting out of breath.
[00:28:28] Jonathan Wolf: Got it. So what is then the level beyond which I could see you clearly wanting us to achieve while recognizing obviously maybe not everybody can?
[00:28:36] Javier Gonzalez: Exactly. Yeah. So the higher intensity activities, which is when you start to become out of breath and you struggle to string sentences together, that's where you can get some of these longer lasting adaptations where your muscles and your liver and other aspects of your body have changed over time and you've got better blood sugar control in the long term. So the lower intensity activities have immediate effects, whereas the higher intensity activities can actually change our physiology so that we control our blood sugar levels in the long term.
[00:29:10] Jonathan Wolf: What about, people ask a lot of questions always about this difference between things that seem that they're high intensity so that you know things that are heavy versus things that are like running, which also make you breathless, but don't have that same sort of weight.
People often talk about like cardio versus that. Does it matter for this topic around blood sugar?
[00:29:34] Javier Gonzalez: Not really. They do have slightly different effects during the exercise, but if we think about you doing your bout of exercise and then you have your meals later on in the day, they then act quite similarly.
And what they do is that when you do your bout of exercise, your muscles are taking up more sugar out of the bloodstream independent of insulin and all these other hormones. The exercise itself means that it's taking up more sugar out of the bloodstream, but then a second component to that is that the muscle's sensitivity to insulin is heightened over the next day to two days.
So it's a two-pronged effect when you do this higher-intensity exercise, you increase the sugar uptake into the muscle, independent of insulin, but you also increase the sensitivity of the muscle to insulin.
[00:30:24] Jonathan Wolf: So that's very cool. So you're saying it's not just that I get a benefit right now, but actually, this is having sort of this, you know, long-term effect as well.
[00:30:34] Javier Gonzalez: Exactly. And some studies have shown with very vigorous exercise, so 45 minutes of pretty much running as hard as people could. Their blood sugar control was improved for up to three days afterward. So the more intense the exercise, the longer that benefit can last.
[00:30:53] Jonathan Wolf: And do we understand why this is happening both in the next few days and even sort of permanently, like what is going on through the exercise? Because you know, anything that is a long-term benefit sounds great, right? Rather than having to sort of do it, start from the beginning. I always love these stories that you can make permanent improvements, you know, despite the fact that maybe you're not 21 anymore.
[00:31:15] Javier Gonzalez: Yep. Yep. Well, there are two main ways in which the immediate effects of exercise work. One is we increase the blood flow to the muscle, so we're delivering that sugar to the muscle, so it has more to take up. And a second is that we've reduced that store of sugar within the muscle, so that fuel tank is low and that is a stimulus for the muscle to take up more sugar out of the bloodstream and store it and replenish that fuel tank.
The longer-term changes are mainly to do with it, it's a bit like a door that allows entry of sugar into the muscle. It's known as a glucose transporter. The number of those that we have in the muscle can increase when we do our exercise training. And so we have a greater capacity to allow the sugar into the muscle more of those transporters, more doors or to allow the sugar to enter the muscle.
[00:32:09] Sarah Berry: And Javier, for someone like myself, who is very busy with work and kids and doesn't particularly enjoy exercise. Is there any such thing as a silver bullet? Now, I always say that isn't when it comes to nutrition, but you often see on the TV news shows coming out saying, oh, you know, do 90 seconds or three minutes a day of HIIT and that's all you need to do.
What's your opinion on the cheat sheet that I could do in my busy life?
[00:32:36] Javier Gonzalez: Yeah. I think rather than thinking of only exercise, I think every form of physical activity that we incorporate in our life, we should remember, can contribute to our health. So I think people get put off by exercise because it feels like a chore.
It's a, you have to do it for an hour, go to the gym at this time of day, whereas by taking an active commute to work or just going for a walk with friends and doing some of your daily activities, but making sure that you are moving whilst you're doing them if you can, then that can integrate more easily into your life.
And it doesn't feel like you are doing a chore and it doesn't feel like exercise. But whether there's a silver bullet -
[00:33:20] Sarah Berry: - Yeah, that's what I want, please. That's what I want to live with. I know that after every meal, I'm going to sit twitching my legs. That's the biggest take-home for me from this podcast.
But I would like to know, is there anything I can do in five minutes each day alongside the fact I walk the kids to school, et cetera? Is there something I can do in a five-minute break between meetings?
[00:33:42] Javier Gonzalez: I'd, I'd be lying if there was, sorry.
[00:33:46] Jonathan Wolf: Sarah, it's a great question, but it sounds like, Javier sadly, is just going to tell us the truth rather than tell us the story we'd like to hear.
[00:33:55] Sarah Berry: Well, look, we've got two great tips. We've got the tip every 20 minutes I'm going run up and down the stairs, because I work in the loft, so I've got two floors of stairs to run up and down to get my cup of tea. I'm going to twitch my legs every time I eat. I think if I start with those two, it's all about these micro changes that we often talk about. So that's two micro changes that actually aren't going to annoy me too much.
[00:34:19] Jonathan Wolf: Sounds great Sarah. So before maybe wrapping up, I think with Javier, you may already be stealing some of his tips, Sarah. Javier's tips. I would love to talk a little bit about blood fats, which we touched on right at the beginning.
So as well as blood sugar. There are also these fats in our blood and I think cholesterol is the one that everybody tends to know about. Why does that matter? And does exercise have any impact here? Because we tend to always just think and talk about blood sugar. But I think you said right at the beginning that actual exercise also has an effect here.
[00:34:48] Javier Gonzalez: Yeah, it does, and I quite like to compare this to diet because one of the ways in which we might lower our blood sugar levels is by reducing our carbohydrate intake. But if it's quite often replaced by fat intake, and the more fat you have in a meal, the higher the levels of fat in the blood after the meal, the more carbohydrate in the meal, and sometimes the higher the blood sugar levels after the meal.
So there's with diet, there's sometimes a trade. Whereas with exercise, exercise can lower both the levels of blood sugar and the levels of blood fat after a meal. But it does happen in very different ways and over different timeframes.
[00:35:31] Jonathan Wolf: So can you explain a little bit what's going on with the fats and explain a bit what they are and you know, I mean we've got Sarah, one of our world experts here to maybe just help us to unpack this.
[00:35:41] Javier Gonzalez: Yeah, I mean, do chip in Sarah, because you are the expert on this. I guess if I just start, and you can correct me, there are multiple types of fat in the blood, whereas sugar is mainly circulating as a specific thing called glucose. Fats come in different forms and the other difference with sugars is that fats don't dissolve in water very well.
So in our blood, they need to be carried and attached to other things. So they're normally within proteins or bound to other proteins, and that makes them dissolve in the blood and be transported. And one of the main ones is called triglyceride. It's the type of fat in the blood that is released from the liver when we are not eating and goes to the other tissues, to the fat tissue to be stored, and also to the muscle to provide fuel there.
[00:36:33] Sarah Berry: So Jonathan, what we know is when we consume fat in a meal, the fat results in an increase in triglycerides that are circulating the blood. Just like when we consume a carbohydrate-rich meal, it results in an increase in blood sugar or blood glucose as we call it, but it's quite a different pattern of response whilst the blood sugar from the carbohydrate peaks very quickly.
So you get a peak in around 30 minutes in the blood and return to baseline around two hours. The fat from the meal causes an increase in blood fat about four to five hours after you consume the meal. It doesn't return to baseline fasting levels until about eight hours after you consume the meal.
Now, given that we consume multiple meals throughout the day, what this then means is that you spend most of your time in what we call a postprandial lipemic state. Now, I know you don't like me using complicated words like that, so I'll explain what I mean. So what this means is that you are spending your time in this post-meal elevated fat state. So let's say you have your last meal at eight in the evening and your blood fat levels don't return to fasting until eight hours later. That means normally for lots of people, it's only between about four in the morning until about whenever you have your breakfast, like let's say eight in the morning, that your blood fat levels are ever at this kind of fasting level.
And we know that if you have really excessive blood fat responses, then it sets off a cascade of unfavorable effects such as oxidative stress and inflammation. And this is where it's really great that there are strategies that we can bring into play that will allow us still to consume a fat-containing meal without having any unfavorable health effects.
Exercise is one of them like Javier said, but also you can add other foods and nutrients to your meal that can kind of put out this unfavorable effect, be like a bit of a firefighter dumping this inflammation. So we know that different components in the meals like polyphenols, which are chemicals from very colorful fruits and vegetables, can dampen this fire, but also exercise.
[00:38:45] Jonathan Wolf: And so Sarah, there will be people listening who probably say, you know what? I've been to the doctor and he is told me I've got high cholesterol, and I've got too much of the bad sorts of fats in my blood. So they'll suddenly have perked up and there'll be others who don't really know because actually this postprandial effect, you know, what happens after you eat?
You would only discover, for example, if you do one of the ZOE tests that we built in because we think it's very important. I think, you know, for today, what would be fascinating to understand, okay, how could exercise play into this? Because I think in general, you know, my, my dad was told about this, you know, 40 years ago and really advised all about diet.
Javier, can exercise play any role in this as you described it, doing on blood sugar?
[00:39:27] Javier Gonzalez: Yeah, it has just as much an impact on the levels of fat, in the blood as it does with sugars. And it is mainly what you've done the day before though. So, whereas with blood sugar control, it has quite an immediate effect, with blood fat levels, what you did yesterday in terms of the exercise will affect your responses today. So the peak effect happens about eight hours after the last bout of exercise. Again, there are effects of intensity and of the total amount of exercise that you do just before I explain the effect, is probably also worth noting that even if exercise doesn't affect the level of fat in the blood, in a similar way to Sarah mentioned there with polyphenols, regular exercise can increase our natural antioxidant capacity. So it's a bit like you've consumed a load more fruit and vegetables, your exercise increases your body's natural antioxidant capacity, and so, for the same level of fat in the blood, you're probably protected against some of the negative effects, but exercise also lowers that level.
[00:40:34] Sarah Berry: Yeah. And that's just how the polyphenols work as well, Javier, so it's the polyphenols, for example, don't lower the amount of fat, but they put out that fire in the same way that the exercise might.
[00:40:47] Javier Gonzalez: Exactly. Yeah. And then exercise can also lower the level of fat in the blood. It does require a reasonable amount of exercise. So if you are doing low intensity like a walk, then it needs to be about 45 minutes to an hour to have at least the effect that is seen in studies and it can lower it by a substantial amount, by up to 50% the next day.
[00:41:10] Jonathan Wolf: By 50%? Okay. That's enormous. You're not just talking about like a little effect.
That's an enormous effect.
[00:41:17] Javier Gonzalez: It's huge. A, and it seems to be a larger effect on the people who need it the most. So the people who show the biggest blood fat response under normal conditions show the biggest reduction when they've done their exercise the day before. So quite a useful effect.
[00:41:33] Jonathan Wolf: You were saying they need to do a longer walk, but actually if I went for a walk for 45 to 60 minutes, that could actually have this huge impact on how I'm dealing with my fats the next day.
[00:41:44] Javier Gonzalez: Yep. Exactly. And you might think, well, is it because people are in a calorie deficit? They've done some exercise. They're now in a calorie deficit, and so is that the only reason that they've got this better response the next day? But we know that that isn't the case because when that's being controlled for in studies, the calorie deficit has some effect but exercise has an even greater effect than just the calorie deficit. So it's acting in more than just a calorie deficit to lower the levels of fat in the blood.
[00:42:15] Jonathan Wolf: Javier, I'm conscious we've covered a lot of ground and I do want to make sure that I've asked you specifically about your sort of three tips.
So people listen, we picked up a bunch through this conversation, but imagine someone saying, okay, that's really interesting. I really want to do something that is manageable and actionable. So if you had sort of three tips for people who want to manage their blood sugar, maybe want to manage their blood fat as well, you know, using exercise, what would you say?
[00:42:43] Javier Gonzalez: Yeah, so I'd say try to do something every day, no matter what it is, would be point number one. I'd say point number two is if that's something that can only be relatively low intensity, then try to do that after you've eaten a meal. And then point 3 would be if you are able to do higher intensity activity, then you should be able to get some longer lasting adaptations.
[00:43:11] Jonathan Wolf: Brilliant. Javier, thank you very much. I would like to try and do a sort of summary if I can, and we've gone to a lot of different places, so bear with me and I've got two different scientists who are going to keep me honest today. So one thing I heard is that regular exercise like eating loads of fruit and veg, which I love as an analogy.
We heard I think why blood sugar control is important because we need to sort of keep it within a reasonable band. And that actually you can change the way you're managing your blood sugar with a surprisingly low amount of intensity. And then I think the last thing you said was actually, you know what, actually exercise can affect the way we deal with fats as well.
And probably, you know, almost everybody listening, surprise. Particularly because you said it sort of has this magic delayed reaction. So that's extraordinary. So I think the takeaway is, as you said we've got your three tips, do something every day, no matter what it is. If it's low-intensity exercise, try and do it after a meal. But do try and do higher intensity exercise cause it has this long-term effect that can really sustain, and support us. Brilliant. Sarah, was there anything else you wanted to add?
[00:44:21] Sarah Berry: No, I love it. I'm busy twitching my legs here.
[00:44:25] Jonathan Wolf: Javier, we'll all be twitching our legs for the rest of the day. , thank you so much for coming back on and we look forward to getting you back again in the future. Maybe talking about some of the results of these new studies.
[00:44:34] Javier Gonzalez: Great. Thank you for having me.
[00:44:37] Jonathan Wolf: Thank you, Javier and Sarah, for joining me on ZOE Science & Nutrition today. If based on today's conversation you'd like to understand how your own blood sugar and blood fat respond to food, then you may want to try ZOE's personalized nutrition program.
Your ZOE membership comes with our app and access to our nutrition coaches so you can learn how to change your diet and health habits and reach your long-term goals. Your personalized nutrition program is based on our scientific research and the results of your personal at-home test, which includes blood sugar and blood fat measurements.
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As always, I'm your host, Jonathan Wolf. ZOE Science & Nutrition is produced by Fascinate Productions with support from Sharon Feder, Yella Hewings-Martin, and Alex Jones here at ZOE. See you next time.