Running Nutrition: What to Eat Before, During and After

Runner nutrition revolves around one idea: managing fuel. Glycogen stores are limited, and when they run out on a long run, the famous "wall" arrives. That is why carbohydrate and hydration call the shots, although protein still matters for recovery. If you want to fine-tune the intensity of your runs, work out your zones with the heart rate zone calculator.

How much carbohydrate per day for your training volume

The figure is not fixed: it rises with the hours you train. These are the ranges from the consensus of the ACSM, the Academy of Nutrition and Dietetics and Dietitians of Canada (Thomas et al., 2016), also summarised in the review by Vitale and Getzin (2019).

If you run three or four days a week for 30-40 minutes, you are below the "moderate" tier: you do not need to carb-load, a normal diet is enough. What changes with the kilometres is energy expenditure; to see how much you burn on each run, use the calories burned calculator.

Before running

For long runs or races lasting over an hour, the consensus recommends 1-4 g of carbohydrate per kilo 1 to 4 hours beforehand (Thomas et al., 2016). On short runs the benefit is smaller: the review by Rothschild et al. (2020) concludes that eating carbohydrate beforehand improves performance in longer efforts, not shorter ones. If time is short, eat less and pick something easy to digest. The breakfast in the first row provides 90 g of carbohydrate: 1.5 g/kg for a 60 kg person.

During the race: how much carbohydrate per hour

What you eat on the move depends on how long the effort lasts. According to Burke et al. (2011) and Jeukendrup (2014): in hard efforts of about an hour, small amounts are enough, even rinsing your mouth with a sugary drink; from 1 to 2.5 hours, 30-60 g per hour; and beyond 2.5 hours, up to 90 g/h. That top tier requires mixing glucose and fructose, because a single type of sugar can be used at about 60 g/h at most; with both, different intestinal transporters come into play.

• Gels: check the label. Each brand carries a different amount of carbohydrate, and not all of them mix glucose and fructose.
• Spread your intake: the ISSN suggests drinking the carbohydrate drink every 10-15 minutes, not all at once.
• Whole fruit is more filling because of its fibre: in the banana study covered by Naderi et al. (2023), cyclists felt fuller and more bloated than with a sports drink, although they did not perform worse.

Water and sodium: neither too little nor too much

The ACSM position stand on fluid replacement (Sawka et al., 2007) sets the goal at losing no more than 2% of body weight through water deficit: 1.2 kg for a 60 kg person. Because sweating varies a lot from person to person, it recommends weighing yourself before and after to learn how much you sweat; Vitale and Getzin (2019) cite rates from 0.3 to 2.4 litres per hour and an average of 1 g of sodium per litre of sweat. On long or hot runs, a drink with electrolytes and carbohydrate can outperform plain water. The opposite risk exists too: at the 2002 Boston Marathon, 13% of the 488 runners tested finished with hyponatraemia, linked to gaining weight during the race and to finishing times over 4 hours (Almond et al., 2005). For most people, drinking to thirst works (Costa et al., 2019). For your everyday water needs, use the water intake calculator.

• Before: arrive well hydrated; start drinking a few hours ahead, not on the start line.
• During: drink to thirst; in the heat or on runs over 2 hours, a drink with sodium is better than plain water.
• After: replace around 150% of what you lost; if you are 1 kg down, about 1.5 litres over the following hours.
• Warning sign: if you weigh more at the finish than at the start, you drank too much.

After running: recovery

After a demanding run it is time to restore glycogen and repair muscle. The ISSN (Kerksick et al., 2017) puts the protein dose that maximally stimulates muscle protein synthesis at 20-40 g and, if you train again within 4 hours, suggests 1.2 g/kg of carbohydrate per hour; if your next session is the following day, your normal meals are enough as long as they reach your daily carbohydrate figure.

Common runner mistakes

• Trying a new gel, drink or breakfast on race day.
• Drinking at every aid station "just in case": the road to hyponatraemia in long races.
• Falling short on carbohydrate in high-volume weeks: with a need of 6-10 g/kg, it is easy to miss it if you do not keep track.
• Eating something fatty, very high in fibre or very large right before heading out: stitches and discomfort.
• Going over 60 g/h with a single type of sugar: what is not absorbed stays in the gut.
• Running to lose weight and then rewarding yourself because "I earned it": the energy burned on a run is easily cancelled out.

Running to lose weight: the nuance

If you run to lose weight, remember that exercise is only one part of the equation: diet still calls the shots. Run for health and performance, and base your weight loss on a moderate calorie deficit and enough protein. If you cut back, do it in the rest of the day and not in the fuel for your long runs, which is where it shows most in performance.

With a clear carbohydrate and hydration strategy you will run more comfortably and recover better. Log your meals with Renzy (a photo of your plate, or the barcode on packaged food) to see whether you are getting the fuel you need, especially in high-volume weeks.