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Marathon Training Diet: Analyzed By Registered Dietitian

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I’ve run over 50 races, including two Boston Marathons, and thought my nutrition was pretty solid considering how clean I eat. But I was surprised at what a registered dietician had to say about my marathon training diet eats.

marathon training diet

One of my best friends, Christian, is a registered dietitian and also getting his doctorate in Nutrition Sciences. Oh, and he is also the Director of Performance Nutrition for the University of Alabama at Birmingham. In short, the dude is smart and knows what he’s talking about when it comes to sports nutrition. So, naturally, I had him analyze what I eat in a day during marathon training. Here’s what he told me.

sports dietician

If your “what I eat in a day” is a representation of a “normal” day, my knee jerk reaction is that you are not eating enough — by a pretty good bit — to meet your needs. More on that below. But you’re doing a lot of great things already.

Marathon Training Diet: Analyzed By Registered Dietitian

Best Diet For Marathon Training

What You’re Doing Well

  • Keep eating pre-workout

Your pre-run breakfast looked good, especially for someone who is not a fan of eating before morning workouts.

  • Keep taking your iron supplement

Take on an empty stomach with citrus (so long as it doesn’t upset your tummy). Try to avoid caffeine 2 hours before and after you take the pill. Also avoid consuming dairy around the same time. Shouldn’t be a problem for you since you don’t eat dairy!

  • You hydrate throughout the day.

I especially liked seeing that as soon as you woke up, you went straight for a glass of water. Lots of folks are concerned that this will upset their stomach but if you keep it to an 8-12 oz glass at least 30 minutes before running, you should be good to go.

I like to fill a glass with ice and water the night before and put it in the fridge so that it’s already made for me when I am groggy and just want to get back in bed! Plus, the ice cold water really helps me wake up, which makes it a lot easier to eat!

  • You are doing a great job with protein. Yay, happy muscles! This helps build and repair them as you workout.

Not only are you doing a good job with the amount of protein you are consuming, but you do a pretty great job of incorporating protein into each of your meals and snacks throughout the day. As active as you are, it is important to make sure that you are eating high quality, protein-rich foods all day so your muscles have it for use when they need it.

One recommendation is to add some kind of protein snack right before bed. A lower carb protein shake is a great option here. Your muscles do a lot of healing overnight so assuring that protein is around is a smart practice.

  • Dried fruit for the win!

I like seeing that you incorporate dried fruits into your meals and snacks. They are also a GREAT alternative to sports gels during runs as they provide the same burst of easily digested carbs without the added processed sugars. They are also a great source of fiber. Yay, happy colon!

Among other performance deceasing effects, alcohol in excess can seriously mess with your hydration. Stick to 1-2/night when seriously training for a race. And have me over for wine when you do imbibe.

Biggest concern: not eating enough

You are NOT eating enough and need to increase your calories (this is common for most people following a marathon training plan). A few tips to do so:

  • Eat slightly larger portions with meals and snacks. A mix of carbohydrates and proteins is great.

You need to increase your portion sizes just slightly – no need to stuff yourself.

  • Put peanut butter on EVERYTHING
  • Eat an avocado EVERY day

I split mine down the middle and sprinkle with sea salt, fresh ground pepper, garlic powder, and smoked paprika. I mash everything together right in the skin and spoon it out on toast with some halved cherry tomatoes or just eat it by itself!

  • Add a smoothie as your snack (w/ avocado)
  • Snack more frequently

What else to improve:

  • Eat more the night before a big AM run

Since the pre-run meal you have before a longer/more intense workout is so small, its critical to make sure that you have a quality dinner the night before.

We all know carbs should be a staple while training for a marathon. I know you don’t love carbs (unless it’s toast or potatoes) but you need to add in more. Try bagels, rice and crackers. Don’t get so obsessive about clean eating that you under fuel.

Remember, fruits and vegetables are almost entirely carbohydrate, and they’re gluten free. 😉

  • You MUST fuel and hydrate on any run over 45 minutes (I’d consider this a long run)!

11 mile, hour and a half run and no fluid/fuel?! You know better! Remember, any sustained (or higher intensity) physical activity lasting more than 45 minutes needs to accompany fluid and carbohydrate replacement for optimum performance and to avoid bonking.

  • Eat sooner after you finish a workout

Your run ended at 7:35 and you didn’t have solid food until 8:45 (a full hour post run). Remember the “metabolic window.” Post workout, your muscles are torn up, damaged, and looking for some love. That 30-45 minute window after a workout is a critical nourishment period to assist in proper/expedited recovery and stronger/better performing muscles! Replenishing glycogen stores by eating carbs helps your recovery.

  • Get blood work done

It’s especially important now since you are likely at your peak metabolic and physical health. Knowing these values now will serve as a standard by which you can gage your health as you get older.

What happens when you under-eat

  • It’s super important to remember that not eating enough can affect your performance and ALSO lead to illness and injury.

Also, if you happen to be trying to lose weight, under-eating can actually prevent weight loss! This may sound counterintuitive, but it’s been shown in multiple studies.

I actually have a paper in review at the moment on a study I finished last fall examining energy balance and body composition in NCAA division 1 female soccer players. We found that athletes who ate less and less often had greater body fat and less muscle mass than those athletes that ate more and more often!

running nutrition


Since Christian gave me some tough love about my nutrition (which came just in time about three weeks before the Boston Marathon), I took all of his advice. I’ll do another post in more depth about what happened but, in short, turns out he knows what he’s talking about.

Thank you Christian! (Y’all can follow Christian on Instagram here! He posts adorable pictures of his frenchie.)

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    32 responses to “Marathon Training Diet: Analyzed By Registered Dietitian”

    1. I am so intrigued by this! I BQ’d last fall for Boston 2020 & am planning to amp up my fall 1/2 marathon training (including diet) to hopefully get a new PR at the 1/2 & lead right on into Boston training. I am going to follow him because I really think nutrition is where its at for me at my older age approaching 50…and still trying to grasp some PRs! 🙂

      • I’m approaching 50 and have a BQ for 2020 too. I know I need to up my nutrition game. I plan on following him too 🙂

      • I’ve noticed a HUGE difference in how nutrition impacts me, as I’ve gotten “older”, even in my mid 30s! I tend to overeat fats and have to make sure I get enough carbs!

    2. Hah! Love his feedback. Whenever I read a “what I ate” post (from anyone!) I always think “OMG aren’t they hungry??” I guess I eat a lot!! (I’m also running, nursing, chasing a toddler and pregnant, so… you know. Send me all the calories!)

          • Haha at first I read it as “you be much hungry all the time” ? truth!

            When I rave about how good something tastes, my mom jokes “oh does it taste like it has calories in it?”

          • Haha at first I read it as “you be much hungry all the time” ? truth!

            When I rave about how good something tastes, my mom jokes “oh does it taste like it has calories in it?”

    3. Loved this! So informative and I liked the format. You should have Christian guest post regularly! Can’t wait to read the follow up post!

    4. If I could go back to school, I would definitely be an RD. I’m so intrigued by everything. And I, too, am excited for the follow-up post.

      • I totally agree!!! It’s SO fascinating. And there are sooooo many opinions about nutrition out there. I love his balanced — and super informed and well researched — approach!

    5. Hi Teri! Thanks for sharing this post! Super interesting and informative! I have a question about taking an iron supplement. I recently got blood work back that said I was slightly anemic so my Dr. prescribed an iron supplement. I’ve been apprehensive to take it after reading that iron supplements can cause painful stomach issues/problems with digestion. I’m wondering if you’ve experienced that at all and if you have any recommendation as to when the best time to take it is?

      • Hi Haley! Thanks for the feedback and the question. As a sports dietitian working with a lot of female college athletes, I deal with this question/apprehension a lot. If you know yourself to typically have a sensitive stomach, I would recommend taking “Slow Iron”. This kind of iron supplement is engineered in such a way that releases the iron more slowly than a standard release supplement. This often times is a big help for folks with sensitive tummies. You should try to take the supplement about an hour before you eat or two hours after. However, if you find that you are still have stomach problems, you can take the pill with food, just avoid dairy with it!
        Hope this helps!

        • Hi Christian! Thank you so much for the advice! Interesting about “slow iron,” I didn’t even know that was a thing!

    6. This was so helpful. I eat clean prob 99% of the time and am vegan but can see that I really need to bring a morning snack back – I got rid of it awhile ago. Even if I’m not training, I still run about 40 miles per week. I’m 49 and know that even though I take care of myself, I really need to pay attention to taking care of my muscles and bones if I want to be that crazy old lady running down the street 🙂

    7. Awesome! Doubly so because I am about to graduate from Optometry school at UAB. I need all of this advice too, particularly the eating more but also having more protein more often throughout the day. I know i need to but it has been difficult with my schedule (in clinic and not a desk job so rarely time for snacks). That’s going to change this summer though so I’m looking forward to what will happen.

      • Oh man, I actually think about often how lucky I am that with my schedule I CAN fuel easily. It’s gotta be so tough when your day is dictated by others and/or you’re with people and can’t just eat while you’re on a call or something!!

    8. I’ve heard of a few athletes in their 30s (like Sue Bird, still kicking booty in the WNBA at 38) realize they were actually under eating and drastically improve their fitness and resilience by eating more. I’m fascinated by these findings and maybe hoping to translate this into my life somehow. It’s tough to manage training + nutrition + having a full-time non-sports job.

      • I’ve also been focusing specifically on increasing my carbs. I don’t love carbs unless it’s potatoes – but I could eat peanut butter or avocados all day. It is so tough to manage it all but I’ve also found by increasing my carbs that my energy is better, which helps me focus at work better and run better!

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