What to Eat Before and During a Long Run

What should you eat before a long run?

Eat a carbohydrate-focused meal 2-3 hours before you start, and keep it low in fat, fiber, and protein so it digests fully before you're moving. Carbohydrates are your body's preferred fuel for running because they convert to usable energy faster than fat or protein, and a mostly-carb meal 2-3 hours out gives your stomach time to empty before impact.

Good pre-run meal options: oatmeal with banana, toast with jam or honey, a bagel with a little peanut butter, or rice with a small amount of protein. If you only have 30-60 minutes before you run, switch to something smaller and simpler — a banana, a few dates, or a slice of white toast. The closer you eat to your start time, the lower the fiber and fat should be, because both slow digestion and raise the odds of cramping or nausea mid-run.

If your long run is first thing in the morning, you don't need a full meal at 5 a.m. A small carb snack (15-30g, like half a banana or a few crackers) right before heading out is enough for most runners going under 90 minutes; your glycogen stores from the day before cover the rest.

What should you eat during a long run?

For runs under about 90 minutes, water is usually all you need — your stored glycogen can cover the effort. For runs over 90 minutes, aim for roughly 30-60g of carbohydrate per hour, taken in small amounts every 15-20 minutes rather than all at once.

Common sources and their rough carb content:

Some trained runners tolerate up to 80-90g/hour using products that mix glucose and fructose, but as a beginner, starting at the 30-60g/hour range and adjusting based on how your stomach handles it is the more reasonable approach. There's no single correct product — what matters is hitting a carb target you can actually absorb without discomfort.

How much should you drink before and during a long run?

Dehydration beyond about 2% of body mass has been shown to impair endurance performance, so the goal is to limit fluid loss, not necessarily to drink as much as possible. Overdrinking carries its own risk (hyponatremia), so more is not automatically better.

A practical approach: drink 400-600ml (about 14-20oz) of fluid in the 2-3 hours before your run, then sip 150-250ml every 15-20 minutes during runs over 60-90 minutes, adjusting for heat and your own sweat rate. You can estimate your sweat rate by weighing yourself (in dry clothes) before and after a run without drinking — each kilogram lost is roughly a liter of sweat.

For runs over 60-90 minutes, especially in heat or if you're a heavy sweater, add electrolytes (sodium in particular) rather than plain water alone, since sweat carries sodium out with it and low sodium is part of what drives cramping and, in rare cases, more serious issues.

How do you avoid GI issues during long runs?

The single most useful strategy is to practice your race-day fueling in training, using the same products, amounts, and timing you plan to use on race day, well before the event. GI distress on long runs is one of the most common reasons runners drop pace or DNF, and it's largely preventable with repetition — your gut can be trained to tolerate carbohydrate intake, similar to how your legs adapt to mileage.

A few other habits reduce risk:

• Start fueling early — in the first 30-45 minutes — instead of waiting until you feel hungry or low on energy, since by the time you feel it, absorption is already behind.
• Avoid high-fat, high-fiber, or high-protein foods in the 2-3 hours before running; they sit in the stomach longer and are a common trigger for cramping.
• Cut back on caffeine and alcohol the night before if either has historically upset your stomach.
• If a product causes bloating or nausea in training, swap it out — don't wait to discover that on race day.

If you have a diagnosed digestive condition or you get severe GI symptoms regardless of what you try, that's worth discussing with a doctor or sports dietitian rather than solving through trial and error alone.

What should you do nutritionally after a long run?

Refuel with a mix of carbohydrate and protein within about 30-60 minutes of finishing, and rehydrate steadily over the next few hours rather than all at once. This isn't about a narrow "window" you'll miss — it's about restarting glycogen replenishment and muscle repair sooner rather than later.

Fueling is only part of recovery. How you cool down matters too — see how long your cool-down should be after running — and pairing good nutrition with sleep and easy movement helps you recover faster after a long run. If your legs are still sore days later, that's usually a training-load issue rather than a fueling one; is it ok to run with sore legs covers how to tell normal soreness from something that needs rest.

What can fueling advice NOT do for you?

Getting your nutrition right reduces the risk of bonking and GI distress, but it doesn't fix mechanical problems. If you're dealing with recurring injury or discomfort tied to your stride, no amount of pre-run oatmeal will address that — that's a form question, and something like how to change your foot strike safely is a better starting point.

It's also worth being honest about individual variation: carb tolerance, sweat rate, and sodium needs differ meaningfully between runners, and the ranges here (30-60g carbs/hour, 2-3 hour meal timing) are starting points, not fixed prescriptions. Some runners need more, some need less, and the only reliable way to find your number is testing it in training over several weeks.

Fueling guidance also isn't a substitute for individualized care. If you have a medical condition affecting digestion or blood sugar (like diabetes), are managing disordered eating, or experience GI symptoms severe enough to affect daily life, talk to a doctor or registered sports dietitian before building a race-fueling plan. And if fatigue, cramping, or GI issues are new, worsening, or paired with other symptoms, that's a reason to get checked out rather than adjust your gel brand.

Frequently Asked Questions

What's the best snack to eat right before a long run?

If you have 30-60 minutes before you start, keep it small and simple: half a banana, a few dates, or a slice of plain toast. Low fat and fiber matter more than the specific food — the goal is quick-digesting carbs that won't sit in your stomach.

Do I need a sports drink for a long run under 90 minutes?

Usually not. Runs under about 90 minutes can typically be fueled by water and your existing glycogen stores. Carb intake during the run becomes more useful once you're going past that 90-minute mark.

How do I know if I'm dehydrated during a run?

Common signs include unusual fatigue, dizziness, dark urine after the run, or a heart rate that feels high for your pace. Losing more than about 2% of body mass in fluid has been linked to reduced performance, which you can estimate by weighing yourself before and after a run without drinking.

Can eating the wrong thing before a run cause a stomach ache?

Yes — high-fat, high-fiber, or high-protein meals close to a run digest slowly and are a common trigger for cramping or nausea. Sticking to simple carbs 2-3 hours out, or a small snack closer to start time, lowers that risk.

How many carbs should I eat the night before a long run?

For most recreational long runs, a normal carb-containing dinner is enough — you don't need a special 'carb-loading' protocol unless you're preparing for a marathon or longer event. The bigger lever for a long run is the meal 2-3 hours beforehand, not the night before.

Sources

• American College of Sports Medicine — "Nutrition and Athletic Performance (Position Stand)"
• International Society of Sports Nutrition — "ISSN Position Stand: Nutrient Timing"
• British Journal of Sports Medicine — "Carbohydrate intake during endurance exercise"
• Academy of Nutrition and Dietetics — "Fueling for Endurance Exercise"