ZOE Science & Nutrition - Most replayed moment: The Impact of Ultra-Processed Food on Young People | Dr Andy Chan

Episode Date: June 2, 2026

Today we’re exploring the impact of ultra-processed foods on young people. One of the big reasons ultra-processed foods have become so widespread is convenience. They offer quick, easy meals for people short on time - and few groups are more time-pressed than parents trying to feed young children. But does this convenience come at a cost? I’m joined by Harvard professor Dr Andy Chan, whose research is helping us understand how early exposure to ultra-processed food can shape future health. 🌱 Try our science-backed and tasty wholefood supplement Daily 30+ Get our brand-new app and Gut Health Test designed by world-leading gut health and nutrition scientists to build healthy eating habits 👉 Join ZOE Follow ZOE on Instagram. 📚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 Eating for Better Brain Health: Your brain-gut blueprint How to eat in 2026 - Discover ZOE’s 8 nutrition principles for long-term health 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 here Listen 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. One of the big reasons that ultra-processed foods have become so widespread is convenience. They offer quick, easy meals for people short on time. And few groups are more time pressed than parents trying to feed young children. But does this convenience come at a cost? I'm joined by Harvard professor, Dr. Andrew Chan, whose research is helping us understand how early exposure to ultra-processed food, can shape future health. There's some new studies that say around 50% of the food that we cook at home is now ultra-processed.

And so that says it's not just, you know, when we're out and about, we should need to be worried about what we're buying in the supermarket and taking home. Yeah, I mean, I think that this is evolving. I think ultra-processed food has been a moniker that's been thrown around to classify foods in a somewhat simplistic way. I think you're right. I think in most people's conception, to process food conjures up images of the bag of unhealthy chips or Doritos or the fast food

meal that you have on the go. I think those are kind of the classic conceptions of what ultra processed food is. But I think that we are understanding more and more that alter processing and that terminology can be a bit misleading because I think there are different ways to think about ultra processed food and there are different ways to think about food processing more generally and also different ways to think about how those different components of food actually influence our health. So I'd actually love to go down to this individual study that you published very recently on ultra-processed food that you ran at Harvard because I think it helps us to understand one of our most common listener questions, which is like, are these ultra-processed

foods making us sicker at a younger age? And I understand that you chose a very particular a group of people to study, namely kids. Why did you choose to study kids? Because I think children are really active, so surely they can get away with eating a lot of this sort of junky food without bad effects. Well, I think that this really came out of our desire to understand a little bit more about why we're seeing this trend in obesity rates. We've clearly seen in the U.S. and other countries that obesity has risen dramatically in the population. And it's not just adults. It's also younger people. So we're also seeing rates of childhood obesity really rise dramatically as well. But the reasons for why we're seeing that increase in obesity have been so

clear. I think there's been an assumption that we're just eating more. But to the point, I think in the last several decades, we've actually seen that probably caloric intake in general may actually be, you know, not shifting dramatically, that it's not just we're eating more calories, but that there might be some differences in the types of calories we're eating. So we really wanted to kind of understand why are we seeing these dramatic shifts in obesity rates, particularly in younger people. In addition, we're also seeing that there are dramatic differences now in rates of chronic disease in younger adults that we haven't been seeing before. So we're seeing more and more rates of cancer in younger people. I think that that's an area that I've particularly focused on

is trying to understand what are the reasons for why younger people are getting cancer. So because of that, I think that there is maybe this shift in risk factors that are happening at younger ages. That may be some of these things that we're thinking about as being risk factors for disease later in life are actually shifting into younger ages. So I think we need to really focus and have more attention on what younger people and children are being exposed to and not just adults. And Andy, is it only cancer that is increasing in younger people? That's been the most dramatic change. You know, we're seeing dramatically increased rates of different types of cancer

and younger people. I think that's been a very noticeable trend. But I think we're also seeing, you know, changes in other types of conditions as well. As a gastroenterologist, for example, we're seeing rises in, you know, inflammatory diseases of the bowel. We're seeing rises in inflammatory bowel disease, for example. We're seeing obviously changes in overweight obesity. over time, we're seeing also consequences of that, rising over time, like diabetes, et cetera. So I think we're seeing a lot of these sort of metabolic diseases and inflammatory diseases

happen at earlier ages, and that probably reflects what we're seeing in cancer as well. And when you say younger people, the older I get, the more I want that to include me. What do younger people mean is you're talking about that as a doctor and a scientist? Yeah, I mean, I think for cancer in particular, we generally define early onset cancer and younger adults as being less than 50, because in the past, I think we'd kind of consider cancer to be a disease primarily affecting people over the age of 50. And that's really why most of the common cancers that we screen for, we start that screening at the age of 50. And so I think in the sort of common definition of early onset cancer for our studies, we've really been focused on people younger than 50.

Could you maybe summarize the study what you did in the findings? Yeah, so we really were wanting to focus on, as you said, younger people to kind of understand what are younger people being exposed to in terms of risk factors and how does that affect not only their health as young people, but in later life. So we wanted to develop this study within a cohort of younger people that we've been following longitudinally since they were very young over time. So it's called the Growing Up Today's study, and these are a group of children that have been followed because they were offspring of mothers who were already in a study, which is called the nurse's health study too, and these were a group of female nurses in the U.S. that have been tracked with questionnaire

data since the early 1990s. So this is like a 35-year study at this point? Right. So we have a unique opportunity to look at this group because we have data on the mothers and we also have data on their children tracked over the last 30 years. And so having sort of that combination of data is really unique and being able to then really pinpoint risk factors not only in the kids when they're growing up, but also look at risk factors in the moms at the same time. And also even some of the things are exposed to when they were pregnant with those kids. So we have kind of data on both the moms and the kids. So we really wanted to look at what the diets of these kids were like

and what the diets of the moms were like and assess whether diet and the things they were consuming affected their risk of developing overweight obesity later in young adulthood. So we carefully looked at information, tracked on what they were eating, and then assessed whether a substantial component of their diet was related to consumption of what we would consider ultra-processed food, and then assessed whether that consumption of ultra-processed food associated with their likelihood or risk of developing overweight obesity in the future.

So what did you find out? It was very interesting. I think we did find there was an association between, child consumption of ultra-processed food and future risk of obesity. Perhaps that wasn't so surprising, but what was very interesting in particular was that it also was associated with the likelihood of their moms eating ultra-processed food during that period of time where they were raising their kids, and it was sort of an independent risk factor.

So what the kids were kind of exposed to in the household seemed to actually have a direct influence on whether they were subsequently at higher risk of developing. obesity. We did some additional work looking at the association of, you know, moms diets when they were pregnant with their kids. There seemed to be some association there not quite as strong, but it does look like early life factors and particularly maternal risk factors seem to be important in determining a child's health, you know, over time. I heard you mentioned that. It's not just that you're eating more calories if you're eating this UPF, if I understood rightly, that sort of the quality of the food is something that, you know, you were saying actually really

makes a difference. And could you help us to understand that? Yeah, I mean, I think what it implies is that a kid's diet has to do with what they're eating, but also has to do with what other foods are being consumed in the house and kind of what they're exposed to. So sort of, you know, everyone's diet is also in part not just their individual food choices, but also what food they have access to. So the idea that a household's access or a household's propensity to be eating ultra-processed food influences or later health, I think, is an important message. In addition, I think that that sort of shows kind of a practical association, but also there's biological questions as well. Is there exposures that might be related to differences in exposure to ultra-process food,

for example, in utero? A mom's diet, does that influence? their kids' health, yes, certainly in the short term. I think we know that a mom's diet obviously affects, you know, the newborn period, but does it also have potential effects downstream from that? And it does raise interesting questions about that because it is possible that some of the sort of short-term, you know, dietary exposures that someone is exposed to when they're, you know, in utero, what we call biologically imprinted, such that it has an influence on their later health status. And that's, I think, a really interesting possibility. and one that's being explored more and more.

You're working on this team that's studying the rise of these early-onset cancers. You think that diets in general and potentially UPFs in particular might be part of this rise? Yeah, I think that that's definitely something we're seeing in the data. I think in some of our early studies, we're starting to see evidence that consumption of UPFs does have a role in sort of the likelihood at someone's developing an early-onset tumor. So we in particular, for example, did a study to look at the consumption of ultra-processed food in younger adults and did see that there was an association between that consumption and the likelihood of having a colon polyp, which is a precursor to colon cancer at a younger age.

And so I think that that's provocative and interesting data to suggest that some of the trends we're seeing with obesity and it's linked to early onset cancer may in part be related also to, diet and ultra-process food consumption. And, Andy, you're very calm, as you say that, but if I just understood what you said, you're saying consumption of UPF, like eating more UPF, is associated with a higher risk of my getting tumors in my body. Specifically, these colon polyps, yes, yeah. We don't want to be alarmist.

I think these are colon polyps that are not cancers. These are cancer precursors. So in large part, they're being diagnosed by individuals and being removed to prevent that cancer from developing. So I think there is still something actionable for people to do. But I think it does raise this question, again, of, you know, we see this in humans. Can we also see if this is something that holds up in some of our animal models and our experimental models to kind of get at the mechanism again to understand sort of why that might be something we're seeing? And is there something specific about the foods that are, you know, playing a role in this risk? And then the other component of that

research, which I think is sort of consistent with what you're doing at Zoe, is trying to understand, are there specific types of UPF that may be more harmful than others? So some of these early classification schemes are really good starting points because it helps us to frame the question and it helps us to do some of the initial work in this field. But I think we are at a point where we're starting to identify within categories of NOVA, within categories of EPF, there's probably differences in sort of the potential detrimental effects. And so, you know, we, for example, want to take some of these UPF categorizations and see, do they link up with specific changes in some of the biological markers of, you know, overweight obesity or biological markers of heart disease or

cancer? And, Andy, this is because UPF is very complicated, isn't it? It could be like there's all these different preservatives and all these emulsifiers and all these sweeteners. And then there's a stuff that they don't even have to put on the label to do with just how they might take a raw material that seems normal like, I don't know, a grain, and they can sort of smash it up and reorganize it. And they can still call it a grain, but actually it doesn't look anything like the chemical did before. So that's a lot to try and figure out, isn't it? Yeah, and we don't know what steps in that process are harmful, like, and what has been, you know, created. Is it necessarily harmful? It may not be. So I think we need to test that.

So it's going to be keeping scientists busy for a long time? I think so, yeah. Brilliant. Well, look, I would like to transition now to sort of actionable advice. Yeah. You know, I think anyone listening to this is probably saying, you know what, I definitely wouldn't want to increase the amount of ultra-processed food I'm eating, and I'm interested in reducing it, you know, for myself and probably for my family. But we also started by saying, well, like, half the food that you're cooking at home probably has ultra-processed food in it. So is it inevitable, or is there things that people could do to, you know, reduce their consumption that don't really? require some completely radical change to how they live.

I think I wouldn't say 50% of the food were cooking at home is ultra-processed. I would say 50% of the food were kind of consuming as a society, maybe ultra-processed. I think in general, kind of a rule of thumb that I like to think about is that if you are able to make it at home on your own in a way that would appear to be in your kitchen, that that probably is a diet and a food choice

that is less likely to be ultra-processed. That being said, I mean, there's things that we're probably cooking at home that do have levels of processing. But I think for the most part, those are easier for us to identify. And I think in general, if we're creating food in our kitchen and it's something we prepared in our kitchen, it probably is less ultra-processed. And when you say prepared, we're taking a packet out of the fridge and putting it in the microwave and turning on for three minutes as the meal, right? Does that count as, is that the making it at home? From raw ingredients, prepared from its original ingredients as opposed to something that you're sort of heating up. Got it.

Because I think one of the things that we've seen is that those sorts of ready prepared meals could often be incredibly high in ultra-processed food, like much more than you would expect. I think part of this is because they're trying to sort of preserve it all and make it last much longer than it would do if you, you know, you made your, you know, spaghetti and meatballs or whatever it is at home. The fact that it looks like a sort of home-cooked meal, is that enough to know that it doesn't have quite a lot of UPS in it? I think it's the first step, but I think a more precise way would be if you could make it from ingredients that are more likely to come from, you know, scratch. So if you're making spaghetti meatballs,

if you're using, you know, fresh tomatoes as opposed to a bottled sauce, I think that clearly differentiates a group, a food choice that's, higher in ultra-processed food, you know, the canned sauce versus something that's lower in ultra-processed food. I hope you found the information in this week's episode useful. If you're interested in improving your gut health, you might want to download our free gut guide. It's packed with recipes and science-backed information to help you on your journey towards better health. Go to zoe.com slash gut guide to download it for free. Or if you're looking for another podcast to listen to, we have a lot more in our podcast.

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