ZOE Science & Nutrition - Recap: We need to talk about metabolism | Shawn Stevenson & Tim Spector

Episode Date: December 30, 2025

We often hear people talk about metabolism - whether it’s fast, slow, strong, or sluggish. It’s one of those health buzzwords that’s often said, but rarely understood. Yet understanding metabolism is essential. It influences how we process food, how much energy we have, and our risk of developing health conditions like diabetes, cancer, and heart disease. In this episode, Shawn Stevenson and Tim Spector cut through the confusion. Together, they’ll explain what metabolism actually is, and empower you to take control of yours. 🌱 Try our new plant based wholefood supplement - Daily30+ *Naturally high in copper which contributes to normal energy yielding metabolism and the normal function of the immune system 📚Books by our ZOE Scientists The Food For Life Cookbook Every Body Should Know This by Dr Federica Amati Food For Life by Prof. Tim Spector Ferment by Prof. Tim Spector Free resources from ZOE Live Healthier: Top 10 Tips From ZOE Science & Nutrition Gut Guide - For a Healthier Microbiome in Weeks  Better Breakfast Guide Have feedback or a topic you'd like us to cover? Let us know hereListen to the full episode here

Hello and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. We often hear people talk about metabolism, whether it's fast, slow, strong or sluggish. It's one of those health buzzwords that's often said, but rarely understood. Yet understanding metabolism is essential. It influences how we process food, how much energy we have, and our risk of developing health conditions like diabetes, diabetes, cancer, and heart disease. In this episode, Sean Stevenson and Tim Specter cut through the confusion. Together, they'll explain what metabolism actually is and empower you to take control of yours.

I'd love to start right at the very beginning. Sean, what is metabolism and why does it matter? From a rudimentary perspective, it's converting food into energy. But that's looking at energy through this very isolated vanilla way. You know, there's this entire microcosm of events, and metabolism is really about the sum of all the different pieces that can create and generate energy and that feed into each other. And for me, it's really based on that principle of energy cannot be created nor destroyed. It can only be converted from one form into another.

And so this energy exchange, even if we're looking at that very vanilla version of it, of food is creating energy, where does the food come? come from? What are the pieces and parts of the food that create the energy? And there are other things besides food that are getting converted into energy for us as well. And whether that's body fat, whether that is oxygen and how it relates to all these different pieces, there are literally millions of parts and inputs that determine metabolism. It isn't just food. And even from the perspective of food being used as energy, right? The endpoint being the mitochondria, which we'll get to, I'm sure, and talk a lot about. When we eat a food, it doesn't just become energy. It gets converted

into a currency that our body can actually use. Our body runs on a certain currency. And so there's so much work involved in converting that food into the currency that our body can use. And sometimes that conversion doesn't happen. Our body isn't converting everything that we eat into that currency that we're using. And Sean, could you talk me through that maybe in a very simple way? Like, let's imagine I eat a piece of bread. Let's use actually a good example. Since you mentioned bread, all right, there was this fascinating study published recently in the journal Food and Nutrition research. And they had test subjects to, and this is a crossover study, so everybody's doing both things, to consume a sandwich of either whole multi-grained bread and cheddar cheese

or a sandwich of what they deemed to be ultra-processed food, which was white bread and cheese product. And here in the United States, like craft is a big cheese company. That's what I grew up eating. But it's called Kraft Singles because they can't legally call it cheese. There's not a little cheese in the cheese. And so it's this kind of cheese product, right? And so they had tests up just to consume both sandwiches

at different parts of the study. Now, keep in mind, these sandwiches have the same amount of protein, fats, carbohydrates, and the same amount of calories. But when they ate the two different versions of these sandwiches, very different things happened with their metabolism. In particular, the expenditure of the calories they consumed. So when people ate the processed food sandwich versus the whole food sandwich, they had about a 50% reduction in calorie expenditure or calorie burn after eating that processed food sandwich.

something happened and to create a very simple understanding. It basically created metabolic clogs. It blocked the body's ability to use that energy efficiently and to get rid of it. And so what does our body do? It's going to do what it can to protect us. And if even that means holding on to some of these calories to try to figure out what to do with this later at some point and not to mention all the other pieces that come along with that it's not just the calories from the food and as tim knows this as well there's a lot of other compounds that come along with ultra-processed foods whether this is you know dilates whether this is you know pesticides and all these other things that can disrupt our metabolism and so when it boils down to it if we can

just kind of consolidate this whole idea when we're choosing to eat a certain food it's not just this calorie conversation. And Tim and I talked a lot about this when I had him on my show. It's so much bigger. There are all these, and this is the term I want to share with everybody, epi-caloric controllers. There are these epi-caloric controllers that are determining how our body is processing the food that we're eating. And so today we're going to expand from the conversation of just calories and understand that our metabolism, when it boils down to it, it is the conversion of food into energy, yes. But there are all these other really wonderful factors for us to pay attention to. And today I want to help everybody to just refine it to some very simple

ideas because it can be complex, obviously. There's so many pieces to cover. But today I want to share some of the top things that are the epicoloric controllers that we can apply in our lives to make better choices and to have a more efficient metabolism overall. You looked at these two different meals, it looked almost the same. Like, in theory, they like bread and cheese, bread and cheese. But one is sort of ultra-processed, and one is sort of much more whole-grain and natural and real cheese. And you're saying that metabolism is the way that you convert food into energy. But although both of them had the same number of calories, you think that, like, the metabolism has to be the same.

You're saying that with this ultra-processed food, somehow your body's metabolism was completely different. And it's sort of held on to like a whole bunch of those calories and stored them as fat, basically, whereas with that more natural food, it sort of burnt them up, even though they were the same calories. Did I understand that right? Now, we can't say the study doesn't reveal whether or not it's getting stored as fat, per se. But the body is slowing down its processing of that energy. There's going to be a tendency, especially over time, that more and more, if that's going to get stored as fat. But as Tim mentioned, in the short term, it can just be everything's kind of slowing down. Your body, from my perspective, is just trying to figure out what to do with this stuff, because it is newly invented. and, you know, based on the things we really evolved eating, where we have a level of efficiency,

and our bodies are incredibly intelligent and resilient. So they can figure out how to process that cheese product, you know, if it's forced to. But ideally, is that optimal? Probably not. I think the following question that was one of the top questions that we have was around metabolic health. So just as I think I'm still a bit confused really about exactly what metabolism is, I'm definitely also confused about what metabolic health is. What does it mean?

I love that this is a big part of the conversation today because, you know, when I graduated from college, I studied nutrition, I studied biochemistry, and I was not taught about, quote, metabolic health, all right? It's just like, even in my first nutritional science class, you know, we were, first of all, we were taught the food pyramid. This was the 90s. My teacher, the professor was basically, you know, he came in and he shared that, you know, if you want to lose weight, you expend more energy than you take in, right? As simple as that if you want to gain weight, you consume more calories than you expend. And that was in. If you want to stay the same, they need to be the same. And a little side note, and I don't talk about this often, but my teacher was significantly overweight. I'm not saying that, you know, this was a character flaw or anything like that. But I'm sure that he was. doing a lot of the things that he was trying to teach us, but they just simply weren't working

for him. And he just needed, in his mind, I just need to cut more calories. I need to do better. And we start to punish ourselves because this dogma that we've been taught isn't working out. And it does work for some people. It does work for some people because at the time he's teaching us and he's applying, we need to eat seven to 11 servings of, quote, healthy whole grains every day. And that's the basis of our diet. And so some of the principles that I talk about took from that is basically, you know, if it's white, it's not right. All right. So no more refined carbohydrates. I'm not going to eat this regular pasta that I grew up eating. Let me get whole wheat pasta, right? I'm not going to eat the white bread that I grew up eating in the United States

is like Wonder Bread and Bunny Bread and now I'm going to eat whole grain bread. I'm going to eat a lot of brown food. And this is not taken into account my unique metabolic fingerprint. Right. So these are some of the things that go into our own unique metabolic fingerprint and our own unique metabolic health. And part of that is our own unique microbial fingerprint. And what if somebody has a hard time with their microbial makeup trying to process a lot of these, quote, healthy whole grains? What is that going to do to their metabolic health? What is that going to do to their energy assimilation and expenditure? All this stuff matters. And we can't have this kind of cookie cutter approach to things. And so an example that really, like, it stayed with me for years that I couldn't understand. And I would go to this Chinese food restaurant that was right off campus. And I was, like, wondering why the store owner and their family, I would go around the time when they were having their lunch. And they were, like, eating white rice and, like, steamed vegetables.

And I'm just like, why are they eating white rice? Don't they know that, you know, this is so much better for you to. eat a brown rice. And what it was truly, if you, you know, my wife is from Africa as well, she's from Kenya, and they've been eating white rice for a long time. Yes, there can be parts of the container or the brand of certain things that can add fiber, but they can also be a gut irritant for a lot of people as well. And so I think some people, our ancestors figured out centuries ago that if we want to efficiently process this food without side effects, if we're looking for caloric energy, right, if that's our goal with this thing, we might want to get

rid of this because it can create some gut irritation for some people. And so getting that background education and not being taught what metabolic health is, which is what is right for me right now to efficiently process my food, to feel good, to, of course, a body composition can come into the mix as well. It's like an outpicturing. And your opening like rapid fire question was, can we have outpicturing of fitness and still be metabolically unhealthy? Absolutely. But it is a part of the equation. There are all these different parts. And so, you know, ultimately, and the most recent data here in the United States, and again, I think that the number, of course, it can shift a little bit, but I think it's pretty close. Only 12% of United States citizens are metabolically healthy.

Only 12%. Only 12%. That should be out. like blow our minds. But the question is, again, this is what we're talking about. What does that mean? What is metabolic health? Well, in this particular study, they were looking at, you know, triglyceride levels. They were looking at HDL and LDL ratios. They were looking at, yes, body composition, body fat percentage and things like that. But it's still looking at things through a very small frame. So I'm not going to be the guy that comes on this show and tells you this is exactly what metabolic health is. I have this problem writing books to, you know, to the public to try and explain metabolism.

Yeah. And my editor says, what is metabolism, metabolic health? Well, the best way I described it, and I love your thoughts on it, is it's the energy management system of the body and its efficiency. It's how all the bits in the body work together and how efficient it is or whether it's inefficient and it's having to work too hard to keep the house warm or cool or whatever it is, is keeping it exactly at that right temperature all the time, regardless of what you're doing. Do you think that's a reasonable way to describe it?

Absolutely. Efficiency is such a key word in this, but that can be misconstrued because we can be very efficient in converting that white rice into glucose and shoot up our blood glucose, have a huge response from insulin, yeah, it's efficient to convert that into energy, but is that metabolically healthy for us? And so we've got to take into account that efficiency means multiple things as well. Yeah, it means not having side effects and means not having other things happen to the system that make it go wrong. I'll end this episode with something I think you'll like, a free Zoe gut health guide. If you're a regular listener, you know, just how important it is to take care of your gut.

Your gut microbiome is the gateway to better health, better sleep, energy and mood. The list just goes on. But many of us aren't sure how to best support our gut. I wasn't sure before doing Zoe, which is why we've developed an easy-to-follow gut health guide. It's completely free and offers five simple steps to improve your gut health. You'll get tips from Professor Tim Specter, Zoe's scientific co-founder and one of the world's most cited scientists, plus recipes and shopping lists. straight to your inbox. We'll also send you ongoing gut health and nutrition insights,

including how Zoe can help. To get your free Zoe gut health guide, head on over to zoe.com slash gut guide. Thanks for tuning in and see you next time.