If you've ever wondered whether losing weight is really as simple as eating fewer calories than you burn, this episode is for you. Michelle and Kevin take a fresh look at the famous "calories in, calories out" idea by exploring two fascinating scientific studies that compared ultra-processed foods with whole foods. They explain why the original concept of calories actually came from research on steam engines before making its way into nutrition science, then unpack what modern research tells us about how our bodies really work. You'll hear why people tend to eat hundreds more calories without realizing it when they're eating highly processed foods, even when meals are designed to have similar nutrition on paper. The conversation also covers why whole foods keep us fuller for longer, how chewing and digestion play a bigger role than most people realize, and why calorie counting doesn't tell the whole story. Rather than dismissing calories altogether, Michelle explains how food quality and calorie balance work together to influence hunger, metabolism, and weight management. It's a practical, science-backed discussion that cuts through common nutrition myths and offers a more realistic way to think about healthy eating without making it feel overly complicated.
Registered Holistic Nutritionist
Michelle specializes in healthy aging, plant-based nutrition, disease prevention and lifestyle change. She translates complex nutrition research into practical strategies listeners can actually use.
Curious Beginner & Co-Host
Kevin asks the questions many listeners are already thinking. He helps make nutrition approachable, relatable and tries to keep things light.
Kevin: Michelle.
Michelle: Kevin.
Kevin: I have some news. I have a little mini announcement.
Michelle: Ooh, okay.
Kevin: Do you know what this episode is?
Michelle: Mmm, I know what it's about.
Kevin: No, but do you know what this episode is?
Michelle: No, tell me, tell me.
Kevin: This episode is our Diamond episode.
Michelle: Diamonds are a girl's best friend.
Kevin: Well, exactly. It's our Diamond Jubilee, just like the Queen of England had. Wow, already? How did that happen? 75 episodes. Can you believe it? You've been stuck with me for 75 episodes. Poor you. That's horrible. You have been teaching me and teaching us for 75 glorious episodes and I wouldn't change one of them.
Michelle: It's so fun. I love this so much. Well, happy anniversary. Yes, happy anniversary, Michelle.
Kevin: I've been waiting for the diamonds to come in the mail. I'm kind of, you know, upset that you haven't sent me like a diamond pinky ring or something, but I'll try to get over it.
Michelle: You know, I'm not materialistic like that.
Kevin: Exactly. I am though. So what do you have for us today?
Michelle: Well, today we're not only talking nutrition. We're going to talk about real science, randomized control trials. There's a couple that I think I really want to talk about and they are the gold standard.
Kevin: Or maybe the diamond standard. Oh, maybe. And by gold standard, you mean not TikTok? Correct. Oh, okay. Okay, just to clarify.
Michelle: Do not get your nutrition information from TikTok, people.
Kevin: Yes, this is actual, real science. We are delving into noobs. This is why you love us. So, okay, hit me.
Michelle: I wanted to dive into that question. Do calories matter? I think we've touched on this a little bit in previous episodes and there's a lot of people that are still calorie counting. So I want to look at actual studies where scientists control what people eat and watch what happens.
Kevin: Oh, okay. Cool. Oh, wow.
Michelle: Yeah. Now first, Joe, just to frame this up. I want to take a second and make sure noobs understand where calorie counting came from. So the calories in calories out principle became the bedrock of weight management because it was adapted from the laws of physics and it originated as a way to measure the efficiency of steam engines.
Kevin: No joke. So from steam engines to the human digestive tract. I love it.
Michelle: Well, let me just, I'm going to briefly touch on this history because again, it's so interesting, but the calorie is the exact amount of heat needed to raise the temperature of one kilogram of water by one degree.
Kevin: Right, right. I've heard that.
Michelle: So that comes from an 1800 study that supports steam engines. And at this point in history, calories had absolutely nothing to do with food or human bodies or weight management, right? Fun fact, what we call a calorie is actually a kilo calorie because it's measurement is per one kilogram of water, right? But back then when these physics principles were defined, they just use the term calorie. Sure. Just keep it simple. So that confuses some people when they realize a calorie is actually a kilo calorie, but it's fine. Just keep using the word calorie. So then in the mid-19th century, German physiologists wanted to know how much energy a farm animal consumed versus how much energy it exerted or stored as fat because they were concerned about raising farm animals efficiently. Yeah. And then all of this ended up getting translated to humans when an American chemistry professor who had studied this concept of thermogenesis and animals decided to figure out how it translated to humans. He built a human-sized respiration calorie meter and he put humans inside it and he fed them specific foods and measured their heat output and their waste. And then he concluded that the laws of thermodynamics did apply to humans just like it applied to farm animals and steam engines.
Kevin: Okay, interesting science.
Michelle: I know, right? Science is so interesting. But this is where we got those values. It's four calories per gram for a carbohydrate, four calories per gram for a protein, nine calories per gram for a fat. So that's where that 449 macro value came from. So that was interesting to find out. So much of our nutrition science comes from animals first, right? Right, of course.
Kevin: But I didn't know the steam engine part. So that was cool. From steam engines to farm animals to humans.
Michelle: Before I go off track so that we can get to the study, I just want to summarize this. Therefore, we got calories in equals calories out. That became our idea because of this industrial view that the human body was just strictly a biological steam engine.
Kevin: Right, it isn't.
Michelle: Food was our coal. Metabolism was our furnace and fat was just extra fuel that was stored in the tank. Okay, makes sense. Alright, so that's where that came from. So that's the end of our history lesson.
Kevin: Okay, here endeth the lesson.
Michelle: I just wanted to frame that before we dive into, you know, do calories matter when it comes to weight management with everything that we understand today? Okay. So I thought that was important. Just where did the calorie come from? That's the baseline. Yeah. Now, there was a landmark study on this in 2019 that was kind of a mic drop in nutrition science. It was a metabolic ward study or a food lab study. So the reason this metabolic ward study is important is that previously we could only make assumptions and extrapolations based on observational data like people would record their food diaries everything which is great and that's common in nutrition science because it's very expensive to put people in a controlled environment. However, in 2019 they did. They took 20 adults and they put them inside a hospital for four weeks and they fed them specifically first for two weeks a diet of only ultra-processed foods packaged ready-to-eat foods. And then they switched their diets for another two weeks where they ate only minimally processed foods or whole foods real food. And in this in this study, they were able to eat as much as they wanted. Now, here's the crazy part. Both diets were carefully designed to look exactly the same on paper. Whether they did the ultra-processed food diet or the minimally processed food diet. They got the same calories. They got the same fat. So the same macros and the same sugar salt and fiber. It's just that one was whole and one was not right. Okay. So what happened? What happened? Well, this is what made this a landmark. They determined on the ultra-processed food diet, the people ate about 500 extra calories per day. They were not satiated. They had more cravings. And they gained weight. Of course. On whole foods, they ate less food without trying. They didn't have the same cravings and the same lack of satiety and the subjects all lost weight. Interesting. So what did this mean? Even though the diets were equal on paper with the same calories and the same macros, they got different results. And they concluded from this study that the processed food made people overeat automatically. So one important catch though, Kevin.
Kevin: There always is one.
Michelle: The two diets in real life look different because the whole food diet was very, very clean and it doesn't really reflect how people would actually eat. Right.
Kevin: Okay.
Michelle: So the scientists wondered, was it actually the processing of the food itself or was it just that the diets were so totally different?
Kevin: Right. Of course. It's one extreme to another.
Michelle: Right.
Kevin: It's not very real world.
Michelle: So that's a good question. And that's what led me to the study that I actually wanted to talk about today. Okay, so that first study was considered a landmark because it was the first time we controlled things. It was a rigorous controlled environment and the nutrient matching design was very cool, right? How the macros were all the same.
Kevin: Right. Of course.
Michelle: So in 2025, there's a new study published in Nature Medicine and this newer study tried to answer that exact question. So instead of comparing two completely different diets, they made both groups follow the same healthy eating plan. So this was done in the UK. So they were following the UK eat well guide. So then they only changed one thing, one group again, ate more processed foods, a more ultra processed food diet. Right. And the other ate a more minimally processed food diet, but they were following the same healthy eating plan.
Kevin: Okay. Okay. Makes sense.
Michelle: So there weren't as many variants.
Kevin: Right. It's a little bit more apples to apples, so to speak.
Michelle: Right. Right. So instead of 20 people, this was 55 people, but instead of putting them in a metabolic ward or in a hospital environment, they let the people live at home so that their eating habits were more real life, but they still provided all of the food.
Kevin: Makes sense. Makes sense. A more natural environment. Right. So a lot more things were normal for these people. Exactly. Yeah. Less intrusive study, hopefully.
Michelle: And instead of just doing two weeks on one diet, two weeks on the other, this time each diet lasted eight weeks.
Kevin: Oh, wow. Okay.
Michelle: Yeah. Now, what's interesting, when they did the study this way, both groups lost weight.
Kevin: Oh, okay.
Michelle: Because both diets were more healthy.
Kevin: Right. Right.
Michelle: So their ultra food, but their ultra processed food diet was still following the UK Eat Well Guide.
Kevin: It wasn't extreme ultra processed.
Michelle: So there was, there were still some management around those ultra processed foods.
Kevin: Sure.
Michelle: Okay. So that's very interesting. However, in the ultra processed food group, they lost about 1% of their body weight, but the people on the healthier whole food version lost 2% of their body weight.
Kevin: Okay.
Michelle: So the whole food group lost twice as much as the ultra processed group. Right. So what does that mean? Well, even when eating healthy overall, less processed food still gives you an edge. If you're eating an ultra processed food diet, if you eat less, it still gives you an edge. Not a surprise. So is it the calories or is it the quality of the food?
Kevin: Right. Yeah.
Michelle: But what this tells us is that both matter, but they matter for different reasons.
Kevin: Okay.
Michelle: These two landmark studies show that processed foods do make you eat faster. They, you feel less full and you eat more without noticing because remember they were given all of the food, but then they were given the food within the guidelines, but they gave them more than they needed.
Kevin: Right.
Michelle: And told them eat as little or as much as you want, right? So you were still subject to your cravings and your snacking and everything else, right? Right. But the people that the ultra processed food just ate more without noticing. And you know, this is very similar to the way I eat, Kevin. If I'm sitting on the couch and I'm snacking on grapes, I am going to stop eating grapes sooner than I'm going to stop eating a bag of chips.
Kevin: Yeah, exactly. I'm just telling you the truth. Oh, me too. Me too. Bag of chips doesn't stand a chance in my house.
Michelle: That's why I don't buy them. Bag of chips is my Achilles heel, man. So this principle is the main reason why people gain weight. Makes sense. The smaller factor comes back to how our body burns calories. Because whole foods do take more effort for our body to digest. They are full of fiber. They keep you full longer and they burn slightly more calories during the digestive process.
Kevin: Ah, okay.
Michelle: But that piece of it is actually quite small. It's only about, it makes a difference about 50 to 100 calories per day. But when you put that in the context of a week, of a month, of a year, that adds up, right?
Kevin: It adds up.
Michelle: Yeah, interesting. So when you put all this all together, the people from the processed food diet ate about 500 calories a day more. And the people who are eating the whole foods maybe burn 50 to 100 calories more.
Kevin: Right. So that's like a 600 calorie difference between the two.
Michelle: Right. So the metabolism of the calorie matters. The calories in matters, but it's really the overeating that trumps the metabolism. Interesting. Right? If you eat too much, you eat too much.
Kevin: Yeah, yeah, but I'm wondering, but it's also, it's the metabolism, but linked to the metabolism is the fact that if ultra-processed food is kind of slightly pre-digested for you, then not only will you spend a few fewer calories in digesting it, but you'll digest it faster. So then you're hungrier sooner afterwards, similar to the grapes versus the potato chips example.
Michelle: And there's also that time delay before the, you know, the signaling happens between your stomach and your brain. And if you're eating food, that's more whole, you're going to take more time or you should take more time chewing.
Kevin: Right, right. Yeah, makes sense.
Michelle: And take more time versus processed food. Like you said, it's heavily processed. So it's easier to just scarf it down.
Kevin: Yeah, yeah. It does take more time to eat a grape than to eat a potato chip.
Michelle: Right.
Kevin: Like just physically. So that makes sense that it would, you would eat slower naturally. Interesting. I never thought of it that way. But yeah, that's, that's fascinating.
Michelle: Yeah. And this is almost, this is like Nutrition 101, like first day in nutrition school, where they emphasize, chew your food. Right.
Kevin: Chew your food 20 times, like my mother always said.
Michelle: Chew your food because that will help. That's one way. First of all, you that additional mastication actually helps to pull more of the nutrients out of the food.
Kevin: Right.
Michelle: And then you have that salivary amylase that that is helping to pre-digest things, you know, you just spend more time eating and you have more nutrient assimilation kind of focused versus if you're eating really fast and you're not breaking down. First of all, that's harder on your digestion. That's where some of us end up with digestive issues because everything goes down not masticated well enough and then your your gut goes. Well, the mouth didn't do their job. Your guts doing all the heavy lifting. I'm the pancreas. I have to work harder now to secrete enzymes to break that stuff down.
Kevin: Darn you teeth.
Michelle: Yeah, because those guys in the factory upstairs are slacking on the job.
Kevin: Yeah, teeth do your work. Slacking off on the job up there. Holy cow.
Michelle: So eating a food that's more whole just naturally, you know, it fills us up faster. It fills us up better and it slows us down. Mindful eating can just really help with that and it reduces overeating just innately. So calorie counting alone doesn't reflect either the nutrient value of the food, right?
Kevin: Right.
Michelle: It doesn't tell you where those calories came from. Like you have to be a really diligent label reader to know how many of those calories are from sugar. How many of those calories are from fat, right? When you're looking at processed food, right? You have to really take a look how much salt is in here. If you're eating things whole you don't have to there's no label to read.
Kevin: It's a much easier way to eat because it's lazier because you don't have to read a label on a grape.
Michelle: So but what's really interesting in that in this new study is is, you know, if you stick to the guidelines, if you want to eat food, that's more processed. You can still lose weight like you can't.
Kevin: Right? Yeah. Yeah.
Michelle: Yeah, you can you can gain weight on eating too much healthy food, but you can also lose weight on junk food, but we shouldn't get too excited about that because you can also you can also lose weight by adopting a cocaine habit or alcohol habit.
Kevin: Yeah, but but it but it sort of fits into the overall way of thinking about food and calories and eating that's helpful.
Michelle: Right.
Kevin: I think to understand that it's not just counting five calories in five calories out having that calorie deficit in the day. It really depends on the type of calories and the type of food and what the makeup of that food is.
Michelle: Exactly. And whole foods just make it easier, right? You're making it so much easier on yourself. If this is really your goal, if this is really your goal, then you're you're just going to get to the finish line faster and easier if you do eliminate a bunch of those ultra processed foods from your diet. So there's this there's this one liner that I came across that I really love calories are the math and food quality is what controls the calculator.
Kevin: Oh, that's a good one. I like that.
Michelle: Yeah. Yeah. So so weight loss does depend upon this energy balance. There is some math there but the nutritional value in the nutritional quality of your food is really what dictates how efficient our metabolism burns that energy and manages hunger. So that's the calculator part because we you know, we've got the microbiome in play. We've got metabolic adaptations like as our we go through different stages of life and our our hormones change and our hormone balance changes. There's there's so many factors in play that it's not just about the steam engine.
Kevin: We are not just a steam engine. Yeah, in case anyone was was thinking about that. You are not a steam engine listener, right? Okay. This is fascinating. Thank you, Michelle. That was really really interesting. Yeah, and it really challenged a lot of that common knowledge that I had previously held about everything coming down to just calories and just being the pure numbers and you know, again that you know calories in versus calories out. It's a much broader picture than that. Interesting.
Michelle: Yeah, because you know, I remember, you know being that typical female with post-pregnancy weight and I remember at the time a doctor telling me well, it's calories in equals calories out. So right and and your energy energy expenditure is part of calories out, right? So that's where she said all you can do is eat healthy and exercise and that's all there is to it. But but what we now know like this is long before in defense of that doctor. This is long before microbiome was ever in the picture. Of course. Yeah, like nobody ever talked to me about making sure that you had variety was key and getting you know exposure to different foods and the importance of fiber and the importance of the amount of water that you're drinking along with that. So everything that we've talked about in nutrition for news always leads us to the same place. It's just kind of fun sometimes to pick on one one societal norm or one societal thought and then and really take a look at this expression calories in calories out. Is this still true? Like it is but it's not the whole picture.
Kevin: Exactly. Exactly. Interesting. Well, thank you for busting that myth another myth busted.
Michelle: No problem. Very small rabbit hole because it's summer.
Kevin: Yeah, eggs at who has time for rabbit holes. Okay, but we always have time for dad joke.
Michelle: All right, bring it.
Kevin: So Michelle, how much does a chimney cost?
Michelle: I don't know if Kevin how much does the chimney cost?
Kevin: Well, it's free because it's on the house. Oh my gosh. Okay. Well, thank you again for another great episode of nutrition for noobs. If you listeners have any questions for Michelle or me, but mostly Michelle, you can reach out to us at our new email address. Don't forget. It's a new one. It's hello at nutrition for noobs.com or you can connect with us on Facebook or Instagram at nutrition. The number for noobs. Did you like that? Hello?
Michelle: I still have you in my head trying to do it with the Dutch accent.
Kevin: Hello at nutrition for noobs.com.
Michelle: I really don't think that sounds Dutch. But okay, I'm sure it doesn't Swedish.
Kevin: I I'm pretty certain it doesn't sound Dutch, but it sounds something maybe Martian. I don't know. I don't know.
Michelle: Muppet. It's Muppet.
Kevin: I'm sure. Yes, exactly. It's the Muppet accent. Okay. Well, thank you for listening. Thank you, Michelle. And until next time, eat your greens.
Michelle: Be real everyone and stay cool.
Kevin: This has been nutrition for noobs. We hope you're a bit more enlightened about how your fantastic and complicated body works with the food you put into it. If you have a question or a topic, you'd like Michelle to discuss drop us a line at hello@nutritionfornoobs.com. If you haven't already you can subscribe to the podcast on whatever your favourite platform might be. Also, please consider leaving a review or telling your friends. That's the best way to spread the word. We'll see you next time with another interesting topic. The views and opinions expressed on nutrition for noobs are those of the hosts. It is not intended to be a substitute for medical nutritional or health advice. Listeners should seek a personal consultation with a qualified practitioner if they have any concerns or before commencing any actions mentioned in the podcast.
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