Hi folks, this is a follow-up to the last video I did on nutrition, where we talked about caloric intake and the value of checking in periodically to make sure that we’re actually getting enough food, because it’s not uncommon for runners to underfuel. Calories are obviously only part of the picture, though. What those calories are, in terms of macronutrients, is also really important.
The Role of Macronutrients in a Runner’s Diet
When we talk about macronutrients, we’re talking about carbohydrate, protein, and fat. In this video, we are focusing more towards the end of performance because, in terms of diets, low carbohydrate, high fat diets work generally, and high carbohydrate, low fat diets work generally. There are definitely populations within that that should maybe gravitate towards one rather than the other, and that would be more towards a higher carbohydrate diet, particularly if you’re exercising.
But what we’ve got to be quite careful of sometimes is that we don’t gravitate into the sort of moderate carbohydrate, moderate fat intake because that can leave us feeling sluggish in our training. And also it can drive weight gain.
Caloric Distribution and Macronutrient Ratios for Runners
The numbers I’m going to discuss now should be taken as rough guides, but it is worth checking in periodically to see where we land with our macro splits. In terms of where your calories are likely to come from as a runner, we are generally looking for about 50% from carbohydrates, 25% from protein, and 25% from fat. All of these macronutrients are super important, and depending on a runner’s goals, the ideal macronutrient split might look quite different.
For example, we might be slightly higher in protein if we strength train as well, and we might be slightly higher in protein, maybe for an older athlete, where protein synthesis becomes more difficult as we age, and so we might just need a little bit more of it.
The Importance of Carbohydrates in Endurance Sports
So, let’s focus on the carbohydrates for a moment. Carbohydrates are essentially a type of sugar, and we store sugar within our muscles and use it when we train. That’s why we need to eat when we run on longer runs. That’s why people talk about “hitting the wall” in events like the marathon where we’ve actually depleted our muscle glycogen.
In simple terms, carbohydrates end up in the muscle in the form of muscle glycogen. We can think of muscle glycogen as like a cup within the muscle with the fuel, muscle glycogen in there and the cup continuously leaks. It’s got little holes in it and it’s continuously leaking because we continuously use muscle glycogen. And then every now and then when we eat carbohydrates, we put a little bit more in to top the cup up. But when we do exercise, we tip quite a lot of this muscle glycogen out.
We therefore have to make sure that, over long periods of time, we’re not chronically depleting our muscle glycogen stores. So in other words, the amount we top it up isn’t as much as the amount that we’re using and eventually it just ends up settling quite low and that’s when we can feel quite lethargic on runs. That’s why we need to make sure that, particularly a few days before a longer run, we add a little bit more extra starchy carbohydrates, we have a carby breakfast, we eat carbohydrates on the run. And then after our longer run, we refuel really soon to make sure that those muscle glycogen stores are topped back up.
“Dialling in your macros can make a noticeable difference in your training. There’s no one-size-fits-all prescription though; it’s about finding what works best for your body, training and goals.”
Coach Helen, We Run Running Coach in Leicester
So it is worth checking in every now and then on your caloric intake to make sure that you’re somewhere near, and your macro split to make sure that you’re somewhere near, bearing in mind it will be different for different individuals. But the sort of area that we’re trying to avoid is that moderate carbohydrate, moderate fat, quite low protein. That’s not really helpful in terms of training and can drive weight gain.
So the recommendation for endurance sports is a higher carbohydrate diet just to make sure that our muscle glycogen stores are topped up, which will lead to good sports performance. If you have any questions, please just get in touch. And for now, Happy Running!
Macronutrient Ratios for Runners (Carbs, Protein & Fat Explained)
Definition: A macronutrient ratio for runners (also called a macro split) is the percentage of your daily calories that come from carbohydrates, protein and fat.
What is a macronutrient ratio, in practical terms?
A macro split describes how your total daily calories are divided between carbohydrate, protein and fat. It is not about eating “perfectly” at every meal. It is about looking at your overall week and checking that your intake broadly reflects your training demands.
For example, if you eat 2,400 calories per day, a 50/25/25 split would mean around 1,200 calories from carbohydrate, 600 from protein and 600 from fat. It does not need to be exact, but being wildly off can affect how you feel in training.
Rules of thumb that work for most runners
- Rule of thumb: If weekly mileage or session intensity increases, carbohydrate usually needs to increase too.
- Rule of thumb: If you add strength work, hills, or faster running, protein should be consistent (often nudging toward the upper end of your usual range).
- Rule of thumb: If you feel “flat” in sessions, look at carbs around key runs first before making big calorie cuts.
Why runners usually need more carbohydrate
Carbohydrate is stored in the muscles as glycogen, which is your main fuel source for steady runs, tempo efforts and races. When glycogen stores are low, sessions feel harder than they should and pace drops off earlier than expected.
If you are regularly doing long runs, intervals or back-to-back training days, a higher carbohydrate intake helps you show up ready to train again rather than constantly digging yourself out of a hole.
Protein: recovery, strength and ageing athletes
Protein supports muscle repair, adaptation and strength work. Runners who include gym sessions or hill sprints often benefit from being at the upper end of a typical range.
Older runners may also require slightly more protein because muscle protein synthesis becomes less efficient with age. That does not mean extreme intakes, but it may mean being more deliberate about including a quality protein source at each main meal.
Simple protein checklist
- Include a clear protein source at breakfast, not just carbs.
- Aim for protein within a couple of hours after harder sessions.
- Spread intake across the day rather than saving it all for dinner.
Fat: essential, but easy to overdo
Dietary fat is important for hormone function, nutrient absorption and overall health. The issue for runners is not fat itself, but drifting into a moderate carbohydrate, moderate fat pattern without enough protein.
Fat is energy-dense, so it is easy for intake to creep up without noticing. If carbohydrate intake drops at the same time, performance can suffer even if total calories look fine on paper.
The “moderate everything” trap
A common pattern we see in recreational runners is moderate carbs, moderate fat and relatively low protein. On the surface it looks balanced. In reality, it can leave glycogen stores under-topped, recovery slower than it should be and body composition drifting in the wrong direction.
If you feel sluggish, struggle to hit paces you used to manage comfortably or find weight slowly creeping up despite consistent training, your macro split is worth reviewing.
Examples: how macros might shift with your training
Example 1 (steady fitness): If you run 3–4 times per week (around 20–35km) with mostly easy runs, a 50/25/25 style split often feels fine – especially if you’re consistent with protein at breakfast and after harder runs.
Example 2 (marathon build): If you run 5–6 times per week (often 50–80km+) with long runs and workouts, you’ll usually perform better with more carbohydrate across the week – particularly the day before and the day of key sessions.
How many grams per kg of carbs, protein and fat do runners need?
Some runners find it easier to work in grams per kilogram than percentages. These ranges vary by individual and training load, but they can be a practical way to sanity-check intake.
- Carbs (g/kg): Often higher as mileage and intensity rise; consider pushing carbohydrate up during heavy weeks and before long runs/workouts.
- Protein (g/kg): Keep consistent across the week, especially if you strength train or you’re an older runner.
- Fat (g/kg): Keep adequate for health, but avoid letting fat crowd out carbohydrate during endurance blocks.
If you want a precise grams-per-kg target, it’s worth speaking to a qualified nutrition professional – particularly if you’re training hard, trying to lose weight, or dealing with low energy.
Macros for marathon training
Marathon training is one of the clearest cases where carbohydrate matters. Long runs and marathon-pace work draw heavily on glycogen, and under-fuelling can turn a sensible plan into a grind.
If you’re building for a marathon, consider making carbohydrates the “default” around long runs and workouts (the day before, the morning of, and the meal after). You can still eat well and keep overall calories appropriate – but the timing and consistency of carbs becomes more important.
Macros for fat loss while running
If your goal is gradual fat loss, total calories matter most. But runners often do better when they keep carbohydrate aligned with key sessions, so training quality stays high.
A common approach is to keep protein steady, place more carbs around workouts/long runs, and be a little lighter on carbs on true rest days – without dropping overall intake so low that recovery collapses.
Adjusting macros based on your goal
If your focus is performance (especially longer races), carbohydrate becomes more important. If your focus is building strength alongside running, protein may edge higher. If your goal is gradual fat loss, total calories matter most, but keeping carbohydrate aligned with key sessions can help maintain quality.
There is no single “perfect” macro split. The best macro split is the one that supports consistent, good-quality training and leaves you feeling well-fuelled rather than restricted.
Frequently asked questions
Is 50/25/25 the best macronutrient ratio for all runners?
Can I run well on a low carbohydrate diet?
How do I know if I am underfuelled?
Should my macro split change on rest days?
Do I need to track macros long term?
When should I get personalised advice?
What to do today (3 quick steps)
- Step 1: Note your current training week (sessions + rough weekly mileage).
- Step 2: Track normally for 7–14 days, then look at your average macro split (don’t judge individual meals).
- Step 3: Make one small change (usually carbs around key runs, or protein consistency), then reassess energy and session quality over the next 2 weeks.
Want help dialling it in?
If you would rather not second-guess your fuelling, working with a coach can help you match your nutrition to your training plan. That way, your macro split supports the sessions you are actually doing, not just a number you found online. For more information, see our Running Nutrition Analysis service, and our Running Nutrition Coaching.
