Simple Nutrition Insights

Why Your Diet Isn’t Working: The Science Behind Carbs, Energy, and Performance

• Leonila • Season 2 • Episode 29

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Registered dietitian Leonila Campos and dietetic intern Anna Kwon, M.S. tackle the persistent myths about carbohydrates that plague social media and harm athletic performance. They break down the science of how our bodies use energy during exercise and why cutting carbs can damage both health and performance.

• Macronutrients explained: carbohydrates, proteins, and fats all play essential roles in keeping our bodies functioning optimally
• Your brain and central nervous system run almost exclusively on glucose from carbohydrates
• The body uses three energy systems during exercise – phosphagen (immediate energy), anaerobic (carb-dependent), and aerobic (uses all macros but carbs remain most efficient)
• When carbohydrate stores run low during exercise, the body breaks down muscle protein through gluconeogenesis
• Weight loss from low-carb diets while exercising often comes from muscle loss and water weight, not fat
• General recommendations include getting 45-65% of calories from carbs, 10-35% from protein, and 20-35% from fat
• Pre-workout nutrition should focus on carbohydrates (60-70% of calories) to fully stock glycogen
• Post-workout recovery requires both protein AND carbohydrates within 2 hours (ideally immediately)
• Excessive protein intake can cause kidney strain, dehydration, and leaves less room for nutrient-dense carbs
• Food has no moral value – all foods fit into a balanced, sustainable approach to eating

For nutrition questions or personalized guidance, contact Leo at 559-512-0404, fueledbyleo@gmail.com, or on Instagram @nutrition_with_leonila.


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Speaker 1:

Hey, hey, everybody. Welcome back to another episode in the Simple Nutrition Insights podcast. I am your host, leonila Campos, registered dietitian, and today I am excited to have a dietetic intern with me, ana. We're going to have a really good conversation about carbs and metabolism and all things that you probably don't hear often in social media, so I'm really excited to have this conversation, anna, welcome to the show.

Speaker 2:

Thank you so much for having me, Leo. I'm really excited to be here.

Speaker 1:

So I'll give you an opportunity to introduce yourself and just let the listeners know more about you.

Speaker 2:

Great. Thank you so much. My name is Anna and a little about my background. I studied sports nutrition at Boston University. I then got my master's in nutritional sciences at San Diego State University and I'm now completing my dietetic internship with Sodexo Healthcare, which is how I got to work with Leo during my community rotation. So, as someone who's been active my entire life, I've always been fascinated by the science of fueling our bodies properly, and I have to say I couldn't wait to tackle carbohydrate myths today, because this hits close to home for me our bodies properly. And I have to say I couldn't wait to tackle carbohydrate myths today because this hits close to home for me.

Speaker 1:

Thank you for sharing about yourself, about your background, even though we think, oh, dietetic, intern right, like it's a student, goes beyond that right, obviously, your education, your bachelor's, your master's, and just getting a lot of exposure into the internship. Yeah, I'm excited that you're here and that we're going to talk about this. So can you tell us a bit more about the myths and carbs around this?

Speaker 2:

Absolutely so. For starters, whenever someone finds out that I study nutrition, the first thing they ask is either how many carbs should I eat? Or they tell me I'm cutting carbs. And they tell me that they're so confused by all the conflicting information out there and it breaks my heart because I see this everywhere Influencers and even well-meaning healthcare practitioners with little to no formal nutrition education pushing restrictive keto diets or intermittent fasts, people casually throwing around terms like carbs are bad and, worst of all, I see active individuals and athletes falling for these harmful trends.

Speaker 1:

Yeah, I mean, I could probably be a billionaire by now if I could count all the times that someone tells me oh, carbs are bad, like you said, specifically your athletes. I've had some clients that are athletes or endurance athletes, and they're like oh, I just, you know, try not to eat carbs. And my first reaction is we need carbs and of course we're going to go into it as to why we need them. But you know, it's so harmful not only to their performance but overall health. And so I get a lot of clients to that come to me and say you know, there's so much conflict and information as to why I should follow right. Some say don't eat fruit, others, you know, eat fruit or don't eat carrots, or you know this just bogus information that as nutrition experts, we are frustrated in a way to think that, okay, all this information is making it to the masses.

Speaker 2:

Definitely. Thank you so much for sharing that. And here's the thing this information that's being spread on social media or people just talk about these things very loosely isn't just harmless information. They are conflicting messages that damage people's performances, their relationship with food and their overall health. Growing up as a girl in the early 2000s, I fell for every fad diet out there. I restricted calories, I cut carbs, I feared fats and I completely bought into that toxic good food, bad food mentality. That was, and still is, everywhere, and because of this I got really sick for a long time and it took me years to undo that damage and truly understand how to properly nourish my body so I could do the things I love and actually feel good while doing them. And that's why this work means so much to me. I don't want anyone else to go through what I went through, especially when the science is so unequivocally clear about how our bodies actually work and what they need to thrive.

Speaker 1:

Yeah, thank you for sharing that. It's such a topic that is so close to you, right, and just being vulnerable and open to talk about that. You know you are correct. Sometimes we see all these misinformation and I'm fearful now with social media and kids such a young age being exposed to it, and we're already seeing that, and I saw that more specifically around COVID times. You know there was a lot of patients calling my office for eating disorders or disorder eating because the parents were so concerned about it and so, yeah, misinformation can really really damage somebody or like someone that is an influencer that says, oh, just eat this way, you're going to be like me and we know that it's absolutely incorrect and so we're going to talk about where to get your information from down the line. But, yeah, thank you, anna, for sharing that.

Speaker 2:

I'm so excited to get into it. And just to let everyone know, the good news is that learning about the science and mechanisms of why our bodies need the food that they do is an incredibly effective and critical part of our healing with our relationships with food. So that's exactly what we're here to do today.

Speaker 1:

Yeah, amazing. Okay, let's start with the foundation. For listeners who might be new to Nutrition Talk what exactly are macronutrients?

Speaker 2:

So macronutrients, or macros as everyone calls them, are the nutrients that our bodies need in large amounts, and there are three of them. So we have our carbohydrates, proteins and fats, and each one plays a unique and important role in keeping us live and functioning. So let's start with carbs. When you eat carbs, they break down into glucose, and that glucose is what every single cell in your body uses for energy. What's important to keep in mind is that your brain and your central nervous system run almost exclusively on glucose. Unless your body's in a state of actual starvation, they really can't use anything else effectively.

Speaker 1:

Yeah, and we're not going to leave you here hanging. We're going to give you more information about these shortly, but what about the other two?

Speaker 2:

macronutrients. Yeah, so protein is essentially your body's building material, and it's crucial for muscle repair, building new tissue, making hormones and enzymes, supporting your immune system. The list goes on. Now, while protein can technically be used for energy, it's like using a hammer as a screwdriver it might work, but it's not what it's designed for and it's not very efficient. And then we have our fats, which are actually our most concentrated energy source. So we're talking nine calories per gram, compared to just four calories per gram for both carbs and protein. Now, fats do much more than just provide energy, though. They cushion and protect your organs. They help regulate your body temperature, they're absolutely essential for absorbing fat soluble vitamins, like vitamins A, d, e and K, and they provide essential fatty acids that your body can't make on its own.

Speaker 1:

Amazing. So all three macros are essential. If someone says, you know, cut down a whole macron group, be wary of that, because you have learned that each macronutrient is so essential for survival and for overall well-being. And so if someone is telling you that, run away. Now here's where it gets interesting for our active listeners. Anna, can you break down how our bodies actually use these nutrients during exercise?

Speaker 2:

Great question. So before we dive into how the body breaks down nutrients for fuel, it's important to understand that your body actually has three different energy systems, working like gears in a car, and interestingly, the first system doesn't even need to break down any macronutrients at all. So your first gear is called a phosphagen system, which uses your body's already existing stores of a high energy molecule called adenosine triphosphate or ATP to supply its energy, and this is your pure power system. That kicks in for really short bursts, so we're talking about 10 seconds of maximal exertion. So when you're sprinting off the starting line or, say, lifting a heavy weight, that immediate burst of power comes from ATP and another molecule called creatine phosphate that's already stored in the muscle.

Speaker 1:

I'm sure some years per step automation of creatine. So could you dive into that for a brief moment?

Speaker 2:

Yeah, sure thing. So we can think of ATP like a rechargeable battery that powers everything in your body. But the problem is that your muscles only store enough ATP to last about two to three seconds of all-out effort, and that's where creatine phosphate steps in. So creatine phosphate is stored in your muscles and when ATP loses one phosphate group for energy, it goes from adenosine triphosphate to adenosine diphosphate or ADP, so that phosphate group needs to be replenished. Creatine phosphate is there to donate one of its phosphate groups to regenerate ADP back to ATP, basically recharging your spent battery in milliseconds. So again, the system keeps you going at maximal energy for 10 seconds, and this is exactly why creatine monohydrate supplements are so popular and well-studied. Supplementing with creatine increase your muscle stores of creatine phosphate.

Speaker 2:

But the biggest misconception is that people think creatine directly builds muscle, and that's not quite accurate. So what it actually does is help you push harder during those short bursts of high intensity activity. So maybe you squeeze out an extra rep in your lift or spend a few seconds longer before you start to fatigue. So the key thing to understand is that, while this boost can be helpful, the phosphagen system is only active during the beginning of intense activity. Phosphagen system is only active during the beginning of intense activity. Those first 10 seconds it's your body's first gear and it burns out quickly. So, yes, creatine can help maximize performance in that brief window of explosive effort, but it's not a magic muscle building supplement on its own. It just gives you a little more fuel when you need it most.

Speaker 1:

Yeah, thank you for explaining that and making that distinction. The creatine supplement is not going to automatically create muscle, right? Sometimes they do hear that it's just like protein, right? That you automatically are going to build muscle. There is that progression. You have to still be able to exercise those muscles, but at the same time, creatine can also help you to perform better, to get that extra sprint or just get that extra rep or whatever the case may be, and so it is important to make sure that you are understanding that a supplement is not going to do the job for you. The other important thing, too, is that you want to work with a registered dietitian, a sports dietitian, to help you figure out the specific goals that you have, as well as, if you need supplementation, that you and your dietitian are working together to get you where you need to be. Don't start just adding a bunch of things without really understanding how they are going to help you. Your dietitian has to work with you to make sure that you are doing it in a safe way.

Speaker 2:

That is so, so important. Now we're exercising past those 10, 15 seconds of maximal energy, and then you shift into second gear, which is your anaerobic system, and this fuels high intensity activities that last anywhere from one to three minutes. Here's what's really important for people to know Only carbohydrates can fuel the system. Your body is working so hard, so quickly, that there isn't enough oxygen available for other processes to break down glucose without oxygen and produces lactate as a byproduct. So if you don't have enough glucose available, the result is early fatigue, loss of power and decreased performance. And finally, we have our third gear, which is the aerobic system, which gives you steady energy for longer activities, so anywhere from several minutes to hours and this system can technically use all three macronutrients. But here's the crucial point that people miss Carbs are still your most efficient fuel source, even during longer exercise.

Speaker 1:

Yeah. So when people say, well, burn fat instead, what's the problem with that?

Speaker 2:

So the problem is that relying on fat for energy during exercise is kind of like trying to start a fire with wet wood. So it will eventually burn, but it's going to take a lot more time and effort. Fat needs oxygen to be metabolized and it has to go through these really complex biochemical pathways to produce energy. So while fat is fantastic for fueling you during rest and low intensity activities, when you need energy quickly for and to sustain high intensity exercise, it's just not going to cut it. So what most people don't realize is that stored body fat doesn't just magically turn into energy when you need it. Those fat stores have to be released from your fat cells, then they have to travel through your bloodstream to get to your working muscles and then they have to be processed through multiple metabolic pathways. Meanwhile, muscle glycogen, which is your stored carbohydrates, is sitting right there in your muscles, ready to be used immediately. It's like having kindling right next to your fireplace versus having to go out to the forest chop wood every time you want to start a fire.

Speaker 1:

Yeah, I love the analogies. You're painting this picture of how these systems work and how important glucose is right, how important our carbs are and not to fear them. And this is the part that really surprises people. And I explained what happens when someone cuts carbs but keeps exercising hard.

Speaker 2:

Yeah. So this is where something called gluconeogenesis comes into play. So gluconeogenesis literally means making new glucose. Gluco refers to glucose, neo means new and genesis means creation. So when your carbohydrate stores are running low during intense exercise, your body doesn't just politely switch over to burning fat, like people think it should. Instead, it starts breaking down your muscle protein to create that glucose that your brain and working muscles desperately need.

Speaker 1:

So when people think they're losing fat on a low carb diet while working out hard, they might actually just be losing the muscle that they're trying to build.

Speaker 2:

Exactly, and this is one of the biggest misconceptions out there. When people lose weight quickly on low carb diets while exercising, a significant portion of that weight loss is actually muscle mass and subsequently water weight, not fat. And losing muscle means you're going to have weaker performance, a slower metabolism and recovery is going to be compromised. So if we're still using the fire analogy, it's like tearing down the walls of your house to keep your fireplace going instead of just going to buy some firewood. It'll keep the fire going, but you're destroying the very thing you're trying to build up.

Speaker 1:

Yeah, such a powerful analogy and this affects performance immediately, right?

Speaker 2:

Absolutely so. When glycogen, or stored glucose, in muscles and the liver runs low, everything gets harder. Workouts feel more difficult, you fatigue faster, mental focus drops. Your body is trying to protect itself from completely using up its ATP stores, which you need to stay alive. So studies show that carb availability directly impacts how long you can exercise, how hard it feels and even your mental sharpness. So this is why endurance athletes carb load before races. It's not so that they can be faster, but to maintain their pace longer without crashing.

Speaker 1:

Yeah so carbs are essential, but not all carbs are created equal, right. What should people focus on?

Speaker 2:

So carbs are in more foods than people realize Grains like rice and oats, fruits, vegetables, especially starchy ones like potatoes, legumes like beans and lentils, dairy products like milk and yogurt and, yes, sweet and processed foods too. So for most people, including active folks, focusing on complex, high fiber carbs is a great way to fill your body. They give you steady energy, plus vitamins, minerals and fiber that help with digestion and satiety. So you want to primarily choose foods like whole grains, a wide variety of fruits and vegetables and legumes.

Speaker 1:

And we're not saying here that you should never have this food right, or you should never have sweets, or you should never have XYZ. What we're saying is that the majority of your meals when you think about performance and just being able to give your body those nutrients that it needs to recover, repair and continue to perform really well has to come from your wholesome foods. But hey, if you want a piece of chocolate or a piece of cake, go for it. You're creating this balance.

Speaker 2:

Yes. So as dietitians and future dietitians, it's really important for us to spread this idea that there is no such thing as bad foods. Your body doesn't assign moral value to what you eat. Food is just food, and there's room for the treats you love in a healthy diet. So, when you think about it, your body breaks down all foods using the same digestive processes. So, whether you're eating an apple or a cookie, your stomach acid, enzymes and intestines are doing their job to extract nutrients and energy and get rid of waste. And what's amazing is that your body is essentially a sophisticated detox and digestion machine, so your liver, kidneys and other organs are constantly working to filter out anything that doesn't serve your body. As long as you're consuming things in moderation, your body is remarkably equipped to handle the occasional processed snack or dessert, and that's what these organs are designed to do. So if you enjoy ice cream or chips or whatever your favorite indulgence is, you can and should include these foods in your life.

Speaker 2:

The key is balance and moderation. When you focus on getting your nutrition foundation in first so eating plenty of whole foods like fruits, vegetables, whole grains, lean proteins, healthy fats throughout the day, you're giving your body all the essential nutrients it needs to function optimally. What's really interesting is that when people stop restricting and start approaching food from this balanced perspective, they often find that they naturally want less of those treat foods than they thought they would, because your body is remarkably intelligent and knows what it needs. So when your body is in an energy restricted state, it sends urgent signals to your brain saying I need something high calorie, high sugar and I need a lot of it right now. So what does that mean?

Speaker 2:

If you're constantly on diets, you're cutting out important nutrients and energy. It's not that you don't have a lack of willpower, it's just your body desperately trying to get the energy and nutrients it's been deprived of. It's when we swing to extremes whether that's severe restriction or consistent overeating that we start to feel terrible, both physically and mentally. So instead of labeling food as good or bad, try to think about how different foods serve different purposes. Some foods are nutrient dense and fill your body efficiently, while others are more about fun and pleasure, and both have a place in a healthy, sustainable way of eating.

Speaker 1:

Thank you so much for mentioning that, and you are correct. I get a lot of clients that come to me and say I need to not eat bad food, right, or when I'm good. You know, I work with my clients to understand the words that they're using, because they paint a story, but also how we describe ourselves or how we describe the food choices that we make. It can impact our progress, and so if oftentimes we say, oh, that's a bad food, or I shouldn't have ice cream because I'm being bad, it's the food that we really enjoy, and so then we create this negative emotion about it when we do eat it and it shouldn't be that way. Right, we should be able to create balance and still enjoy those foods without feeling so restrictive or that you know we need to eliminate them. So it is definitely about balance and all foods fit.

Speaker 1:

I do have one tip for active listeners. High fiber foods can cause some bloating if you consume it too close to workouts, right? So if you are an active person, definitely experiment with the timing and just make sure that, whatever you try, never try it on your day of racing or when you're going to compete. That's another time to experiment. You want to add these modifications when you're training, just to make sure that your body is going to respond properly. And just make sure to always stay hydrated when increasing your fiber intake, because it pulls some water, so you need some increasing water as well, especially if you're an active person. Make sure that you are staying hydrated in general. Okay, let's talk a little bit about how much carbs people in general need and what about protein, especially around exercise.

Speaker 2:

Yeah, the truth is there is no one size fits all answer. But for anyone exercising intensely for over an hour every day, we strongly recommend working with a registered dietitian, so specifically a sports dietitian, for that personalized guidance. When you're highly active every day, your calorie and macronutrient needs are going to be higher than those of the general population, so a dietitian can help you develop a personalized plan that supports your goals as well as your nutrient and recovery needs. But in general, the acceptable macronutrient distribution range, or AMDR, is pretty broad for individualization purposes. In general, carbs should make up about 45 to 65% of your total daily calories, protein anywhere between 10 to 35% and fat between 20 to 35%. And endurance athletes do need the same macronutrients as anyone else who's active. They just need more of them to keep up with the demands of their sport. So we won't go into exact numbers that people should be eating in this episode because we don't want to provide a nutrition prescription. This, again, should be done with a dietician. But there are some key principles for feeling well. So in the day leading up to a tough workout so anywhere from four to 24 hours before it's a good idea to focus on eating plenty of carbs. Aim for around 60 to 70% of your total calories, to make sure your glycogen stores are fully stocked.

Speaker 2:

Then, during exercise, especially if it's lasting longer than an hour, it's important to take in some carbs to help maintain your energy levels. And staying hydrated, of course, is also crucial, and we won't get into full details of hydrating here, since it could be its own episode. But I do want to quickly mention that regular sports drinks can be really helpful in this context. While you're exercising, they provide fluids, electrolytes and glucose, which your muscles need to keep going. But, as a side note, if you're sweating a lot and working out for a long time, sugar-free electrolytes electrolyte drinks might not be the best choice. So they don't have the carbs your body needs during prolonged exercise and for some people the sugar substitutes can cause stomach issues. Everyone's different, so it's all about testing what works best for your body. And after exercise, your body is primed to replenish glycogen stores immediately post-workout. This is crucial and often missed. It's important to eat carbs within two hours of a workout, but ideally right away. Waiting more than four hours significantly impairs recovery.

Speaker 1:

Yeah and thank you for really explaining that and making sure that listeners are taking note of that, and so this is where the carb protein combination matters, right?

Speaker 2:

Absolutely. Protein post-workout enhances muscle repair, but it works best with carbohydrates. Together they speed up glycogen replenishment and support recovery. Many people focus only on protein and they end up missing this important synergy Right and we are learning that we need our carbs.

Speaker 1:

So, speaking of protein, many people believe eating more protein than the other nutrient is always better, but that isn't true.

Speaker 2:

Is that right? Yeah, while eating enough protein is important, more isn't always better. Remember, the acceptable range is 10 to 35% of your total calories, but many people go way beyond that and it is simply not beneficial to your body to consume more than this. There are actual problems that can occur with excessive protein intake, including kidney strain for those with any underlying kidney issues, and there's also increased risk of dehydration, since the breakdown of protein in your body requires water, and then this increases water loss through the urine. Many high protein foods also have higher saturated fat levels, which is linked to increased risk of heart disease and certain cancers. And one of the biggest problems with overemphasizing protein intake is that there's less room for carb-rich, nutrient-dense foods like fruits, vegetables, whole grains and legumes. And when you overemphasize that protein intake, you often under-eat carbs, which leads to fatigue, poor recovery, disrupted sleep and, ironically, potential muscle loss through gluconeogenesis.

Speaker 1:

Yeah, so balance is definitely the key for all macronutrients.

Speaker 2:

Exactly so. When it comes to fats, you want to aim for about 20 to 35% of your total daily calories, but the key is focusing on nuts, seeds, olive oil, avocado and fatty fish especially fatty fish because they're packed with anti-inflammatory omega-3s, such as salmon. When you're getting quality fats like these, your body can properly absorb and transport those fat-soluble vitamins we talked about. You're reducing inflammation after a workout, you're giving your brain the nourishment it needs to function optimally and you're supporting all those other critical roles that fats play in keeping your body running smoothly.

Speaker 1:

Thank you for making all the analogies and help us understand the important role of all the macronutrients, because we need all of them. This is why diets don't work well, because our bodies need these nutrients. It's just important that we understand that specifically, if you're an athlete, you need all these nutrients to help you recover, to help you repair and to help you perform better.

Speaker 2:

Yeah, thank you Absolutely. It's so important to keep this information in mind and remember that if any diet touts cutting out entire food groups, that that diet is not only not going to be sustainable, but it's going to harm your body in some way, shape or form. This leads into a very important question Before we wrap up, leo where should people actually get their nutrition advice?

Speaker 1:

Yeah, amazing question. This is so important. Social media is just flooded with influencers, nutrition coaches and even well-meaning healthcare professionals without formal nutrition education giving advice that can cause real harm, especially for active people. So registered dietitians are the only professionals specifically trained in evidence-based, individualized nutrition care. We understand the science, the individual variations and how to optimize both performance and health. You know, if you haven't worked with a dietitian and you're an active person, you need a dietitian in your life.

Speaker 2:

Thank you so much, leo. If you're experiencing low energy, you're not performing well and you just don't know how to meet your needs. See a registered dietitian. So, leo, where can your listeners contact you if they want some advice?

Speaker 1:

Yeah, I do have an Instagram. You can follow me if you like. Nutrition underscore with underscore Leonila L-E-O-N-I-L-A. If you want to send me a text, this might be faster 559-512-0404. Or my email fueledbyleo at gmailcom. I'll make sure to add all this information in the show notes so you don't have to scramble and write it. I'll make sure to add all this information in the show notes so you don't have to scramble and write it, and this has been such an incredible, enlightening episode. Any final thoughts for our listeners.

Speaker 2:

Yes, I hope this episode informs and empowers people to fuel themselves well and to ditch the diet myths once and for all. Carbs are not the enemy. They're your body's preferred fuel source. Embrace them, choose them wisely, time them well and watch your performance excel.

Speaker 1:

Amazing Mic drop. Nothing else to say. But yeah, thank you so much, Anna. That is it, my friends. Thank you so much for joining us. I appreciate you. We'll talk to you and see you in another episode. Bye-bye for now.