Slow carb, low carb, no carb?

Ketogenic and Paleo eating plans are the trendy diets right now, especially among active people.  Because of that, “carb” has become a dirty word.  I can’t tell you how many endurance athletes I work with that have put themselves on low carb diets.  (Spoiler alert- training rarely goes well after that). 

Before we get too far, I need to say that YES- refined carbohydrates and excess sugar are bad.  Many people are also finding they have some sort of gluten intolerance – including my own husband who was recently diagnosed with celiac disease.  

But…If you are riding regularly or training for a race, century ride, etc, you need carbs.  Not everyone should eat the same amount-  some of us need more or less, depending on our own personal tolerance and how active we are.  The bottom line is that you don’t need to take up a keto diet or eat like a caveman to be healthy.  Read on and I’ll explain why.   

The science of workout nutrition:

When you are exercising, training, competing, or just generally being active, your blood sugar (aka glucose) levels are important.  The goal of a good nutrition plan is to give your body what it needs to keep these levels from dropping.  

Blood sugar too low?  You will feel foggy and fatigue faster than usual.  Performance drops- obviously not what we want during a workout.   In a long ride or race you will likely hit the dreaded “wall” we all try to avoid.  

Blood sugar stays steady?  You will feel like you have enough “in the tank.”  You’ll have enough mental sharpness to power though at your best level of performance. 

We store extra glucose (sugar) in our liver and muscles for times that we really need it.  But think of this as a “savings account” at a bank-  if we tap into it, we need to replace the funds at some point.  If we don’t, our body starts to break down its own tissues to repay the debt.   We start losing muscle and lean tissue and throwing our hormones out of balance.   We don’t recover well from training sessions and can get injured pretty quickly.

For optimal workout recovery, we have to put the right fuel source back into our body’s storage account.  Carbs are the best source of this.  Yes, keto fans are correct in saying that the body can also use fat as a fuel source.  In theory, this sounds awesome-  you would avoid blood sugar levels dropping altogether and never have to worry about “hitting the wall.”  But sometimes, theories don’t work as well in reality. Right now, the consensus among exercise physiologists is that fat doesn’t allow athletes to go as fast and as efficiently as possible as using glucose and carbs as a fuel source.   

It’s important to understand that restricting calories or amounts of a certain food source can put extra stress on the body.  We operate at our best when we eat a variety of whole, unprocessed foods.   So diet stress plus training stress can overload the body in a way that can make your performance even worse. 

When should I eat carbs?

Most athletes are successful with eating a well-rounded diet that includes quality carbs before, during, or after exercise.  The right time to eat them depends on your training and your own individual needs.

Carbs before exercise:

  • Fuels the body for training 
  • Signals the brain you are fed and nourished and that you won’t need to tap into the body’s stored energy sources
  • Stimulates the body to release insulin, which works with protein for workout recovery 

Carbs during exercise:

  • Gives immediate energy if you feel like you are losing your mental edge or performance
  • Is important for endurance athletes on long rides, runs, swims, etc
    • *Note- most people don’t need to take in extra carbs during exercise, unless they are participating in long workouts (longer than 2 hours) or multiple training sessions per day

Carbs after exercise:

  • Replaces glucose or fuel the body used for the workout. 

What kinds of carbs are best?

As I mentioned before, processed foods or refined sugars are not great for the body.  These cause our blood sugar to rise quickly and then fall; which helps no one achieve their goals.  Plus this quick spike and drop puts unnecessary stress on the body just like eliminating carbs altogether would.  

Before or after a workout, we want to eat minimally processed, slow digesting carbs.  These are often foods that are high in fiber (also a carb).  Examples of these are:

  • Potatoes and sweet potatoes (which is better?  Check out this infographic)
  • Fruit 
  • Beans, legumes
  • Sprouted bread
  • Bean pasta (also a good protein source!)
  • Quinoa
  • Steel cut oats
  • Barley, millet, wild rice

Fruit gets a bad rap because it contains fructose, but it also contains fiber and good vitamins, minerals, and nutrients (this is different than the awful-for-you high fructose corn syrup found in most processed foods).   We shouldn’t be eating more than 50g of fructose per day, which is equivalent to 32oz of soda, 2 bags of Skittles, or 11 apples.  So if you eat whole, minimally-processed carbs, fruit is perfectly fine to have. 

If you need to eat during a workout, choose something that digests quickly (ain’t nobody got time for stomach issues).   Usually a liquid source like a sports drink or gel is best.  If your ride or workout is intense, longer than two hours, or in hot or dry weather, you will likely need to replace electrolytes too. 

Questions about the best carbs other nutrients to make you feel or train your best?  Contact me or schedule an online nutrition coaching session.


  • Our body needs carbs as fuel for most workouts
  • Most of us feel and train our best when eating a variety of whole, unprocessed carbohydrate sources that are high in fiber.


  1. Berardi, John et al. The Essentials of Sport and Exercise Nutrition. Precision Nutrition, Inc, 2017.
  2. The Ketogenic Diet: Does it live up to the hype? 
  3. Best workout nutrition strategies