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A sports dietitian shares how glucose levels affect energy levels

Expert answers, General health, Type 2 diabetes

A sports dietitian shares how glucose levels affect energy levels

Plus, her top tips for the everyday athlete.

We recently chatted with Anna Turner, MS, RD, CSSD who is currently working as a Sports Dietitian for St Vincent Sports Performance in Indiana. She works with a variety of teams and clients including Butler men's and women's basketball, the Indiana Fever basketball team, and the Colts football team. Her goal is to ensure that every athlete has the basics of sports nutrition available to them in order to leverage their athletic ability. 

Q: Can you share a little bit about yourself and what a sports dietitian does? 

A: Hi! I'm Anna Turner. I'm a sports dietitian with an undergraduate degree in nutrition and dietetics, as well as a master's degree in exercise science. So that makes me a little bit different than other dietitians because I'm taking nutritional knowledge and applying it to exercise science and how the body metabolizes fuel to perform work. And so then my ultimate goal as a sports dietitian is to help athletes learn about nutrition in order to maximize their performance. So obviously maximizing health is important and a part of the plan. But a healthy eating diet is definitely different than a sports nutrition-focused diet. 

Q: What are your recommendations for the everyday athlete?  

A: So when I am assessing an athlete, I ask probably 30 questions (how often are you training, how often are you eating, what are you eating, etc.)  or so in our initial intake and I'm looking at these five areas:

1. Are they fueling frequently?

Is this an athlete who is skipping meals or they fueling up every three to four hours? 

2. What does their plate look like?

I'll talk throughout an "athlete plate" and the three different plates that show how your nutrition changes based on how intensely you're working out. Are you going for a 30 minute jog or you going for a 90-minute run? I'm thinking about how is this athlete building their athlete plate, how does that correspond to the training? 

3. Are they carrying a water bottle with them daily, or if they carry anything at all?

I carry my 32 ounce Yeti with me and as a result I know how many times I need to fill that Yeti up throughout the day to meet my minimum hydration goals. Beyond that, we work on hydrating to replace your sweat losses. 

4. Are they having any recovery nutrition?

For example, a lot of adults work out in the morning, so they might be doing a 5-6:30 am workout and then they have to hurry up and help their kids get dressed and ready to go to school. And then they have to commute to work as well. That can provide a really large challenge in getting recovery nutrition after a workout to help fill glycogen stores and to start the repairing process with protein. It's figuring out what their overall day looks like, and then how we implement nutrition strategies within that.

5. How is this athlete planning?

I go through what they need to eat for breakfast, lunch, dinner and snacks, as well as what they need to hydrate with and how much, but all of that information is essentially useless if they aren't planning and then implementing that plan. So it's important to help them figure out how to create a plan and then utilize it to their advantage. 

Q: Let's talk about blood sugar. First, is how does blood sugar levels affect energy levels and/or fitness performance? 

A: So, your blood sugar levels can and will affect your exercise performance in several ways.
One, in the willingness to even start training. If you are starving or hungry or just feeling low on energy because of a lack of calories (you didn't eat enough during the day or didn't have a snack within an hour to an hour and a half before starting to train), which is causing your blood sugar to start to drop, it's going to be hard to even start the workout. So that's a really big one is paying attention to. Are you excited to go jump on the bike or go out for a run? Do you have enough energy, or do you feel a little sluggish?

That's why talking to athletes about their fueling schedule is really important to help them understand the consistency of fueling and being thoughtful behind putting energy in your body before you're expecting it to give energy out in the form of a workout. 

If you're having hunger signals or feeling light-headed or dizzy, those signals that could indicate your blood sugar is dropping. That's why talking to athletes about their fueling schedule is really important to help them understand the consistency of fueling and being thoughtful behind putting energy in your body before you're expecting it to give energy out in the form of a workout. 
Another way in which you could feel blood sugar glucose levels affecting your performances is in perceived level of exertion, meaning how hard you feel a workout is. Does the workout feel super easy, or does it feel tough and almost like you can't finish it? If you usually crush a workout and today it's just feeling very hard, that could be a pretty good indication.

Perceivable exertion can definitely go up as blood sugar drops, and is very tightly linked to the amount of carbohydrates that you're taking in. Carbohydrates are the main source of energy for athletes and the more you exercise, the more efficiently you utilize those carbohydrates. 
That brings me to a really good point of just getting to know your body. If you are an athlete who is transitioning to a healthier lifestyle, getting to know your body is super important because there are multiple ways to be healthy, crush workouts, eat healthy and not weigh yourself on a scale. Not using a scale as the only predictor of success helps you to be more intuitive in how your body is feeling, how much energy you have, or how restful your sleep is. And being able to crush your workouts can really help you stay on track in a very helpful way. That is highly motivating. 

Q: Are there any other recommendations you have for managing glucose levels while working out?
A: Definitely having that pre-practice snack within an hour and a half to two hours before you train. From there, it really depends on the duration of  your workout. Are you doing a 30-minute HIIT workout, 90-minute trail run or three hour bike ride? It's really after 60 minutes that we need to start to think about putting in more carbohydrates into our system while we're working out. 
Within that first 60 minutes, that would be where we've kind of run through our glycogen stores within our muscles. And now we're getting to the place where we need that external carbohydrate to continue to have even level blood sugars. That's why it's important to be very mindful and intentional about the duration of your workout, so that you can then plan your nutrition. 
There is one story that I love to tell because I learned so much about myself even though it was an awful experience. I went on a bike ride with a group of friends, but the one cyclist who usually leads the way and doesn't get us lost wasn't there so my two-hour bike ride ended up being a four-hour bike ride. I did not pack enough food and I bonked. So bonking is just complete draining of energy, essentially draining of the glycogen that your body can use for immediate fuel. So then your body has to go to other sources like protein and fat and it's just much slower to convert that so your output in your exercise is just going to totally tank. I could hardly turn over the pedals on my bicycle. I had never experienced that before in my entire life, but I'm also happy that I did experience it because it taught me a ton about what my body feels like when it needs fuel and obviously what happens when it doesn't have it. So definitely take those moments as learning experiences. And you can use them to learn about what your body is telling you. 

What nutrition advice do you have for athletes who have pre-diabetes or type 2 diabetes? 

So with prediabetes and type 2 diabetes, I think one of my biggest recommendations would be to really ensure that you have a varied diet; you're not just eating one fruit or one vegetable on a daily basis. We're thinking beyond macros into really the micros of nutrition and making sure that we are getting in all of the vitamins and minerals that we need to really help all of the systems of our body run effectively. That's just one of the things I always like to bring up is challenging yourself to eat a very varied diet and choosing five fruits and vegetables to rotate throughout the week so that you're getting in different nutrients from each food and you're giving your body the best possible chance to thrive on all the nutrition that it does need.
Secondly, I would say for someone who is starting to add more exercise into their life to utilize sports nutrition rules such as a pre-practice snack or even adding in carbohydrates  after the 60-minute mark of a workout. However, I would do that with the asterisk of listening to your body because you can learn so much by doing so and it will help you apply those sports nutrition rules in a more tailored way that fits your specific case. 
With sports nutrition rules, there are so many variabilities. For example, one of the rules is to eat a balanced snack within two hours of training. But obviously, if you ate a bigger lunch and you're not hungry for that balanced snack, it would be less necessary. You have to think through how does this apply to my life and what my body's telling me? 

You have to think through how does this apply to my life and what my body's telling me?  

I will say that that's one of the things that I didn't do well before I became a sports dietitian. I was a competitive athlete so I knew my body really well and I did listen to my body when it came to exercise, but when it came to nutrition, I just assumed that I didn't know anything. And so I remember specifically one race where I had put so much pressure on myself to win because it was in my hometown. I got so nervous that I was Googling all the stuff I could possibly do to help me and one of the sports nutrition rules is carb-loading. So I ate so much more oatmeal than I normally would for breakfast that morning. I had read that carb loading is really important to build up my glycogen stores for the race and I thought if I ate eat more, then I'd have more energy throughout the race. Normally, I might eat like one bowl, but I ate two bowls. I thought the logic was sound, but realistically it didn't work out because I overfilled my stomach. Come the start of the race, my stomach was still full and that is not how any athlete wants to start a race. 
So that's why I say research and look at sports nutrition rules, but also apply it to your own life and know that what your body tells you is valid and you need to consider that as well.
Becoming more intuitive with yourself helps you figure out what low blood sugar feels like, what high blood sugar feels like. If you're someone who is on a continuous glucose monitor, you have some really good information. You can then utilize that information and also write down how it's making you feel so that when you're not testing, you know in your mind, "Oh, this is what 120 feels like". All of that is really good information that will help you have great, consistent exercise routine and energy levels.  


Q: What are a few common misconceptions people have about nutrition and fitness? 

A: One of the biggest misconceptions that I find with athletes is that they assume that as exercise increases, protein increases. There are some cases where protein does need to increase, but most of the time as exercise and duration increase, it's carbohydrates that actually increase.


Athlete platesImage source:


When an athlete comes into my office, I will teach them these three "athlete plates" (see above) that are adapted from the US Olympic Committee. The plate on the left is for the athlete who is an adult who works out for 30-45 minutes (or less) of cross training like a 30-minute easy run or 45 -60 minutes of easy cycling or the elliptical. I like to call this the standard American athlete plate. Most of us have a non labor intensive job and we work out for 30 to 45 minutes a day, and this plate is 100% on point for that. 

So to me, it's not that carbs are bad. It's aligning carbohydrates with the appropriate exercise level to have ultimate success.

As an athlete starts to train more (perhaps for a half marathon), we need to add a little bit more carbohydrates (see the middle plate). You'll notice the fruits and vegetables decrease and carbohydrates increase. And then for the plate on the right, if we're training for a full marathon or an Ironman, we need to increase carbohydrates again. You can see that protein stays the same throughout all three of these.

So that's definitely one of the biggest misconceptions; societal views on carbohydrates are that they are bad and make us make us sick, which can be the case. But that's when you're not balancing what our body considers as fuel (carbohydrates) with exercise, which would be the output. So one way in which I always describe that is if you were eating the plate on the right, but you're exercising like plate on the left, you're over-fueling your body because you are eating too many carbs. Or you could be doing the opposite where you're eating like the plate on the left, but you're training for the plate on the right. You're likely going to come into some chronic fatigue issues and maybe even weight loss because you're under-fueling. So to me, it's not that carbs are bad. It's aligning carbohydrates with the appropriate exercise level to have ultimate success.


Q: Thank you for all of this incredible information! How can someone reach you to learn even more about sports nutrition?
A: If you want to learn more about sports nutrition or want to have a personalized plan created for you, you can reach me at an
You can also reach me on Instagram at AnnaTurner_SportsNutrition. We have a ton of fun things going on right now. Currently we have a hydration tune-up. So that is a two-week crash course on putting together building out your hydration plan. So if you have ever noticed that you do really well during your shorter runs or bike rides during the week but your weekend bike rides and runs just tank and and you aren't sure if it's your fuel or if it's your hydration, that's a really good time to come get assessed. Let me help you build out that perfect hydration plan so that you can complete those really long but super awesome workouts on the weekends.