What to eat before, during, and after a run

Most runners learn what to eat the same way: by experimenting with whatever they can stomach at 5 a.m., and gradually deciding what doesn't ruin the run. That works fine for a 5K. For anything longer, the decisions matter more, and the gap between what works and what shows up in your Instagram feed gets uncomfortable.

What the actual research supports is more specific, and at least one common rule is wrong. Below are the numbers from the position stands the field itself reads, simple rules to follow, and the 30-minute "anabolic window" the literature retired a decade ago, even though the supplement aisle never got the memo.

Before a run

Past roughly an hour, the pre-run meal starts to matter. The position stands have a specific answer.

The International Society of Sports Nutrition's 2017 position stand on nutrient timing recommends consuming 1 to 4 grams of carbohydrate per kilogram of body weight in the hours before a longer, higher-intensity session. Sports nutrition recommendations are written in kg, so if you think in pounds, divide your body weight by 2.2 to get kg. Then multiply by 1 (the floor) and by 4 (the ceiling) for your range.

The wide range is the point. The bottom of it can be as small as a banana, a bowl of oats, or a piece of toast with jam. The top is a full pre-race meal, hours out.

The same paper also bucked the common "eat 2 hours before" rule. Carbs eaten 30 minutes before exercise often produced better outcomes than carbs eaten 120 minutes before, depending on individual tolerance. Some runners do better with a smaller meal closer to start time. Some get a stomach ache. Your gut is the variable nobody on Reddit accounts for. Practice it in training, not on race morning.

The simple rule: for runs under 60 minutes, eat what your stomach will tolerate. For runs over 60 minutes, eat something carb-leaning in the hours before, and figure out by experiment whether your stomach prefers it close or far.

During a run

This is the section most people get wrong in both directions. Beginners obsess over fueling on a 5K. Marathoners ignore it for too long on race day.

The threshold is around 70 to 90 minutes. Under that, mid-run fueling mostly doesn't help. Past that, glycogen stores start running low and performance falls off, sometimes catastrophically.

The position stand's recommendation for longer-duration exercise is 30 to 60 grams of carbohydrate per hour, ideally in a 6 to 8 percent carbohydrate-electrolyte solution, every 10 to 15 minutes. A standard energy gel is around 25 grams of carbs, so one gel every 30 minutes after the first hour gets you in the recommended range. So does sipping a sports drink steadily, since most are formulated in the 6 to 8 percent range.

That 30 to 60 g/hour band is for runs roughly 1 to 2.5 hours. Above 2.5 hours, the research on highly trained endurance athletes supports going higher (some elite ultrarunners reach 90 g/hour with mixed carbohydrate sources), but for most amateur runners, 60 g/hour is the realistic ceiling without GI distress.

After a run

This is where popular advice and the actual research diverge most.

For decades, the standard belief was that you had a 30 to 60 minute "anabolic window" after exercise: eat protein in that window or lose most of the benefit. Aragon and Schoenfeld's 2013 review in the Journal of the International Society of Sports Nutrition quietly demolished this. Their conclusion was that "evidence-based support for such an 'anabolic window of opportunity' is far from definitive," and that the next regular protein-rich meal, whether it happens immediately or 1 to 2 hours after, is generally enough to maximize the benefit. The window is wider than the supplement industry needs it to be.

That doesn't mean post-run eating doesn't matter. Two things still do.

Carbohydrate, if you're training again within 8 hours, helps replenish glycogen faster. The 2017 ISSN nutrient timing stand recommends about 1 gram of carbs per kg of body weight within 30 minutes after, then again every 2 hours over the next 4 to 6 hours, for fast recovery between same-day sessions. For most runners who train once a day, this is overkill. The next normal meal does the job.

Protein, on the other hand, has clearer evidence. The 2017 ISSN protein position stand by Jäger and colleagues recommends a per-meal dose of 20 to 40 grams of high-quality protein, ideally containing 700 to 3000 mg of leucine, distributed every 3 to 4 hours across the day. A normal recovery meal with chicken, fish, eggs, tofu, or a protein shake gets you there. There is nothing magic about doing it inside 30 minutes.

The daily picture

Almost everything described above is in service of one bigger number: total daily protein and carbohydrate intake. Specific timing is a small variable on top of that.

For exercising adults, the 2017 ISSN protein stand recommends 1.4 to 2.0 grams of protein per kg of body weight per day for building or maintaining muscle. Multiply your body weight in kg by 1.4 and 2.0 to get your daily range. For most adults, that lands in territory you can hit with normal meals containing real protein sources at breakfast, lunch, and dinner, not a supplement program.

Carb targets shift with training load, per the 2016 ACSM joint position statement on nutrition and athletic performance (Thomas, Erdman, Burke). Light training days (under an hour of running) sit around 3 to 5 g/kg/day. Hard or long training days move toward 6 to 10 g/kg. Race weeks and ultra-distance blocks push higher.

Why your gut acts up

Runners are the most-studied athletes on exercise-induced gastrointestinal distress, partly because running has the unfortunate distinction of being the sport that does the worst to your stomach. The Costa et al. 2017 systematic review consolidates the evidence under the label *exercise-induced gastrointestinal syndrome*, and three mechanisms keep showing up.

First, blood flow to the gut drops sharply during exercise as the body diverts circulation to working muscle. Prolonged underperfusion of the gut lining is the leading proposed driver of the cramps, nausea, and (in extreme cases) bleeding that long-distance runners report.

Second, every footstrike mechanically jostles the contents of the GI tract. Running is the only major endurance sport that shakes the gut with every stride; cycling and swimming sit gentler at the same intensities, and consistently produce fewer GI symptoms in the same athletes.

Third, high-osmolality fuel compounds both effects. Energy gels and concentrated sports drinks pull water into the gut to dilute themselves, which is exactly the opposite of what a stressed gut needs. The 6 to 8 percent carbohydrate solution recommended for mid-run fueling isn't arbitrary; concentrations above that band consistently produce more GI symptoms in studies.

The practical response is the same set of rules you'd already follow. Train your gut on the same fuel you'll race on. Avoid high-fiber, high-fat, or unfamiliar meals in the 2 to 3 hours before a hard effort. If gels give you problems, dilute them with water at the same time, or shift to a steady sports-drink sip pattern instead of pulses.

TL;DR

For most runners, on most days, the rules are simple.

1. For a run under an hour, eat what works for you. Water before, water after. Don't overthink it.

2. For a long run over 90 minutes, eat a carb-leaning meal 1 to 3 hours before. Carry a gel or a small flask of sports drink. Take in 30 to 60 g of carbs per hour after the first hour.

3. After any hard session, eat your next meal within the next couple of hours, and make sure it includes 20 to 40 g of protein and some carbs. The exact minute does not matter.

4. Across the whole day, aim for 1.4 to 2.0 g/kg of protein, distributed across 3 to 4 meals. Carbs scale with training load.

Hit those numbers and you have done more than 90 percent of the optimization the research actually supports. The rest is your stomach's call.

Sources and further reading

• International Society of Sports Nutrition Position Stand: Nutrient Timing (Kerksick et al., JISSN 2017)
• International Society of Sports Nutrition Position Stand: Protein and Exercise (Jäger et al., JISSN 2017)
• Nutrient timing revisited: is there a post-exercise anabolic window? (Aragon and Schoenfeld, JISSN 2013)
• American College of Sports Medicine Joint Position Statement: Nutrition and Athletic Performance (Thomas, Erdman, Burke, MSSE 2016)
• Systematic review: exercise-induced gastrointestinal syndrome (Costa, Snipe, Kitic, Gibson, Alimentary Pharmacology & Therapeutics 2017)