Fueling Easy Runs vs Hard / Long Runs

sarah cuff Endurance Sport, Performance, Running Performance Leave a Comment

While traditional advice for runners has long been to eat ~60-65% of your diet from carbohydrates, after working 1-on-1 with hundreds of runners and hearing from thousands over the past decade, I do not believe this often recommended high-carb advice serves the majority of runners. To maintain our health and prevent injury over the years, as well as ensure optimal performance, it appears the best strategy is to implement nutrient timing and bookend only your hard runs and your long runs with carbohydrates. Easy runs, which technically ought to make up about 80% of your training, do not need to be fueled with an excess of carbs.

Not all runs are equal and as runners we do our long-term health a disservice if we try to fuel each run the same way. It’s likely eating too many carbohydrates also hinders many of our short-term health not to mention any weight goals also. (That said, please note there are very specific cases where I do find fueling all runs, even easy runs, with carbs can be helpful – for a short period of time until the health condition being addressed is resolved.)


Unlike hard or long runs, your easy runs can be fueled nearly entirely by fatty acids – one of the (many) benefits to working out in your aerobic energy system! However, for those just getting into running or for those who eat a chronically high-carb diet (such as is the traditional recommendation!), the body is not primed to burn fat for fuel as its default and therefore it’s optimal to take time to ‘train’ your body to become a better fat-burner. 

Another term for becoming a better fat-burner is becoming more ‘metabolically efficient’ – whereby your body is able to access the plentiful fat stores on your body for fuel (everyone, even the leanest of runners, has over 135,000 calories worth of fat stored on their bodies – whereas no one is able to store more than about 2,000 calories worth of carbohydrates at one time). 

Easy runs (that is, when you run at a HR between 65-79% of your HRmax [maximum heart rate]; or below 180 minus your age [MAF]) are the perfect opportunity to help train your body to become more metabolically efficient. When you go out for carb-depleted or fasted runs, you are helping your body learn to access fatty acids for fuel. Typically, the first few weeks of carb-depleted runs can feel challenging, as your body goes through the physiological changes of making new enzymes and learning how to utilize fatty acids for fuel. 

Even more metabolically efficient runners stand to benefit from incorporating carb-depleted runs. For example, a 2012 study published in the International Journal of Sport Nutrition and Exercise Metabolism followed 3 of Canada’s top elite marathon runners for 16 weeks and found that 2 to 5 fasted runs (low-CHO-availability training bouts) per week resulted in marathon personal bests come race day (2:11:23 and 2:12:39) and a successful marathon debut (2:16:17).

Here’s some examples on how to successfully incorporate carb-depleted training sessions into your weekly training schedule: 

Morning Easy Runs: if you are waking up and running first thing in the morning, this is the easiest way to run carb-depleted. Simply wake up and head out for your fasted run. Do not drink or eat anything except for a bit of water, black coffee or black tea (in other words, avoid calories in any form prior to going out for your easy run). To intensify the effect, you might also choose to have a low carb dinner the night before (skip the starchy carbs and just have protein with veggies and healthy fats). 

Afternoon Easy Runs: if you run at lunch (that is, just before eating lunch), either practice IF (intermittent fasting) and skip breakfast, or aim to have a low carb breakfast that morning before your run (such as Paleo Coffee/Matcha or an egg scramble cooked in butter and served with avocado). Either skip having a morning snack or have a low carb snack such as a handful or two of nuts, grass-fed beef jerky, smoked salmon or hard-boiled eggs. 

Evening Easy Runs: if you aim to do your carb-depleted run in the evening, ideally, you’ll want to eat low-carb all day – at the very least skip the carbs at lunch and as above, either skip having an afternoon snack or have one that consists of nuts, avocado, jerky or boiled eggs. 

I do always recommend immediately following any run with recovery nutrition – in this case after an easy run, aim to have a complete meal including a good source of protein, lots of healthy fats, and fruit or starchy carbs if desired.


Any run that is faster than ‘easy’ pace means that we step out of the aerobic zone and into the anaerobic zone. The only fuel that powers the anaerobic zone is carbohydrates (glucose). Therefore, it’s imperative to ensure muscle, liver and blood glucose levels are topped up and steady before going into a tempo, interval or progression run. 

Long runs (defined as longer than 75 minutes for typical carb-fuelled runners; and longer than 2.5 hours for more metabolically efficient runners) also need to be fueled, as our glycogen stores are limited, thus need to be topped up before going out, and then restocked while we are out running. Even metabolically efficient runners burn a small percentage of carbohydrates while running easy, so anyone running long enough will eventually need more carbs to keep going.

We can fuel our hard and long runs well by ensuring the last 1-2 snacks / meals we have before the run are primarily made up of nutritious carbohydrates.

To dial into how to best fuel your speed workout or long run, let’s look at specific examples.

Morning Run: if you’re waking up and running first thing, you do need to ensure you eat beforehand. Depending on the amount of time you have before your run starts determines the food you’ll be able to digest. Keep in mind if you currently think you’re unable to eat pre-run, you won’t be able to perform at your best until you train your gut to be able to. The good news is that the gut is highly trainable! Here are some examples: 

Eating 20-45 minutes in advance, such as waking up at 5:30am for a 6:00am run: have 2-3 medjool dates with a bit of nut butter and washed down with water or tart cherry juice. Ensure anything consumed pre-run is primarily purely carbohydrate based (such as fruit such as banana or dates, gels, fruit juice, candied ginger, energy drinks).

Eating 1-2 hours in advance, such as waking up at 6:00am for an 8:00am run: you might have a bowl of instant oatmeal, cooked oats or oat based granola, with berries or dried fruit and a sliced banana and some juice or tea/coffee. Anything consumed 1-2 hours or more in advance gives the body more time to digest everything, so the meal can include protein and fat as long as it’s still mostly made up of carbohydrates (such as oats, rice, quinoa, potatoes, fruit, sourdough bread). 

For both options above, if your run is going to be particularly hard (more than ~20-30 minutes of actual speed work) or very long (longer than ~3-4 hours), you might also ensure your dinner the night before includes a serving of rice, potatoes, yams, quinoa, beans or lentils or other nutritious whole food starchy carbohydrate. 

Afternoon/Evening Run: Your pre-run snack should be easier to digest (primarily carbohydrates with just a bit of fat/fibre/protein), such as a Chocolate Beet Muffin or a Power Cookie with a matcha tea (or green tea). Or date/nut energy balls or bars, or a piece of fruit with some nut butter.

If your run is going to be particularly hard (again, more than ~20-30 minutes of actual speed work) or very long (longer than ~3-4 hours), you’ll want to ensure your lunch and your afternoon snack are primarily carbohydrate based. Lunch can contain more protein, fat and fibre as it’s farther away from the run (such as a rice or quinoa-based power bowl / burrito bowl, or wild salmon with rice and veggies, or grass-fed steak with mashed potatoes and veggies). Just ensure there’s a good serving of yam, potato, rice, quinoa, lentils or other complex starchy carbohydrate on your plate.

I encourage all runners to consume recovery nutrition ASAP following a long or hard run. A recovery shake is a popular option, such as the Chocolate Cherry Berry Recovery Shake, as we often find ourselves without much of an appetite or desire to eat food after speed workouts or longer runs. Whatever your choice of nutrition is, just ensure it contains 40+ grams carbohydrates, 15-25 grams protein and some healthy fats.

With a little planning in advance, you’ll find you can land on a schedule of fitting in carb-depleted / fasted runs to help you become more metabolically efficient while ensuring all hard or long runs are adequately fueled with carbohydrates for optimal performance and recovery. As your body becomes stronger and healthier for it, you will find your performance only continues to progress to the next level.

To deliciously healthy food and stronger faster running,

Sarah Cuff, R.H.N.
Holistic Sports Nutritionist
Run Coach
Therapuetic Coach

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