How to Gain Weight as a Runner
If the scale keeps drifting down while your mileage goes up, the math is usually simple: your runs burn more than you add back at the table. This guide shows how to put a number on that gap, how much extra food closes it, and how to split those calories between carbohydrate, protein and fat so the weight you gain supports your running.
- Your runs add hundreds of calories a day, so eating like a non-runner leaves you short.
- Estimate maintenance with the calculator, add about 300 to 500 calories a day, then adjust from your weekly average weight.
- Keep protein at 1.2 to 2.0 grams per kilogram and let carbohydrate cover the rest of your training fuel.
- Add strength training on at least 2 days a week.
Why runners struggle to keep weight on
Running burns energy fast. The Compendium of Physical Activities, which its authors describe as a global standard for the energy cost of activities, rates running at 6 to 6.3 mph (a 10-minute mile) at 9.3 METs. One MET is the energy you use at rest, about 1 calorie per kilogram of body weight per hour. So a 150-pound (68 kg) runner at that pace burns roughly 630 calories in an hour, and about 565 of those are on top of what they would have burned sitting still.
Over a week of training that adds up quickly. Thirty miles at a 10-minute pace is five hours of running, or around 2,800 extra calories a week for the same runner: about 400 a day that have to come from somewhere. If they do not come from food, they come from your body and the scale moves down.
Sports scientists call what is left after the cost of exercise energy availability. The International Olympic Committee's 2023 consensus statement explains that when it stays too low for too long, it can lead to Relative Energy Deficiency in Sport (REDs), which can affect metabolism, reproductive function, bone and muscle health and immunity. It also warns that no single cutoff fits everyone, so the practical goal is to stop the slide first, then rebuild.
Runner fuel calculator
Enter your details and a typical week of running. The calculator estimates your everyday needs, adds what your runs cost, then adds a surplus. It covers adults aged 19 to 59, the range of the adult Compendium.
Your estimate
Estimates only. The National Academies report an average error of 266 calories a day for the men's equations and 191 for women's, and the Compendium authors call their values a starting point, not a precise measure of one person. Your weekly average weight is the real test.
How the calculator works
Everyday baseline. The adult "inactive" equations from the National Academies' 2023 Dietary Reference Intakes for Energy. Men: 753.07, minus 10.83 times age, plus 6.50 times height in centimeters, plus 14.10 times weight in kilograms. Women: 584.90, minus 7.01 times age, plus 5.72 times height, plus 11.71 times weight.
Your runs. Distance and pace give your hours. The calculator takes the Compendium running row closest to your speed, multiplies its METs by your weight and hours, then takes away 1 MET per hour, because the baseline already counts your resting burn. For example, 25 miles a week at 9:00 per mile is 3.75 hours at 6.7 mph, rated at 10.5 METs.
Target. Baseline plus the daily average of your runs is maintenance; the surplus sits on top. A 30-year-old man, 5 feet 10 inches and 150 pounds, running those 25 miles gets a baseline of about 2,543 calories, about 346 a day for running, maintenance of about 2,889 and a target of about 3,289 with a 400-calorie surplus. Cycling, swimming and lifting are not counted, so add them separately.
Add a surplus you can keep up
The NHS advises adults who want to gain weight to do it gradually, adding around 300 to 500 healthy calories a day. For a runner that surplus sits on top of the running calories, not in place of them. The NHS tips:
- Eat smaller meals more often, with healthy snacks between meals.
- Add extra calories to meals with cheese, nuts and seeds.
- Have high-calorie drinks, such as milkshakes, between meals, but do not fill up on drinks right before you eat.
- Add protein with beans, pulses, fish, eggs and lean meat.
- Do not rely on chocolate, cakes and sugary drinks to gain weight.
Then let the scale steer. Weigh yourself at the same time of day a few times a week and compare weekly averages. If the average has not moved after two or three weeks, add another small snack a day.
Carbohydrate, protein and fat for runners
The NIH Office of Dietary Supplements sums up what athletes need each day: carbohydrate of typically 3 to 10 grams per kilogram of body weight to maintain blood glucose and replace muscle glycogen, protein of 1.2 to 2.0 grams per kilogram, and fat at 20% to 35% of total calories. For comparison, the Dietary Guidelines for Americans, 2025 to 2030 set a general protein goal of 1.2 to 1.6 grams per kilogram per day.
The calculator splits your target inside those ranges: protein at 1.6 grams per kilogram, fat at 30% of calories and carbohydrate for the rest, checked against 3 to 10 grams per kilogram. For the example runner (68 kg, 3,289 calories):
| Nutrient | Rule | Grams a day | Calories |
|---|---|---|---|
| Protein | 1.6 g per kg | 109 | 435 |
| Fat | 30% of calories | 110 | 987 |
| Carbohydrate | The rest (6.9 g per kg) | 467 | 1,867 |
| Total | 3,289 |
The joint position of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine sets amounts for different training scenarios and recommends a registered dietitian for a personalized plan. For protein alone, try our protein calculator.
Calorie boosters for runners
The easiest extra calories pack a lot of energy into a small volume. The CDC explains why: fat has 9 calories per gram, more than twice the 4 in carbohydrate and protein, while water adds weight but no calories.
| Food | Portion | Calories | Carbs | Protein |
|---|---|---|---|---|
| Granola, homemade | 1/2 cup | 298 | 32.9 g | 8.3 g |
| Bagel, plain | 1 medium | 277 | 55.0 g | 11.1 g |
| White rice, cooked | 1 cup | 205 | 44.5 g | 4.2 g |
| Pasta, cooked | 1 cup | 196 | 38.3 g | 7.2 g |
| Peanut butter, smooth | 2 tbsp | 191 | 7.1 g | 7.1 g |
| Oatmeal, cooked with water | 1 cup | 166 | 28.1 g | 5.9 g |
| Greek yogurt, plain, whole milk | 6 oz | 165 | 6.8 g | 15.3 g |
| Baked potato with skin | 1 medium | 161 | 36.6 g | 4.3 g |
| Whole milk | 1 cup | 149 | 11.7 g | 7.7 g |
| Medjool dates | 2 dates | 133 | 36.0 g | 0.9 g |
| Raisins | 1 small box (1.5 oz) | 129 | 34.1 g | 1.4 g |
| Olive oil | 1 tbsp | 119 | 0.0 g | 0.0 g |
| Banana | 1 medium | 105 | 26.9 g | 1.3 g |
Source: USDA FoodData Central, SR Legacy. Portions use USDA gram weights.
Stir olive oil into post-run rice or pasta, spread peanut butter and banana on a bagel, carry trail mix or raisins on long runs, and drink whole milk between meals; the Dietary Guidelines advise full-fat dairy with no added sugars. More ideas: calorie-dense snacks and pre and post-workout nutrition.
Lift weights too
The Physical Activity Guidelines for Americans advise muscle-strengthening activities of moderate or greater intensity that involve all major muscle groups on 2 or more days a week, such as lifting weights, resistance bands or push-ups. The NHS notes that strength training builds muscle and that exercise can also improve appetite. See gaining weight and muscle together.
When weight loss is a warning sign
Some weight loss when you add miles is expected. The NHS says to speak to a GP if you have lost weight suddenly, if you have lost weight without changing your diet or exercise routine, or if you use the control of food to cope with feelings, because it could be a sign of an underlying health condition.
The IOC describes REDs as a clinically diagnosed syndrome that can affect reproductive function, bone and muscle health and immunity, so tell your doctor about missed or irregular periods, repeated injuries or frequent illness too. For a personal plan, the joint position statement notes that in the United States and Canada, the Certified Specialist in Sports Dietetics (CSSD) is a registered dietitian and credentialed sports nutrition expert.
Frequently asked questions
- Why can't I gain weight as a runner?
- Usually because your runs burn more than you eat back. At a 10-minute mile, 30 miles a week can cost a 150-pound runner around 2,800 calories on top of normal life. Cover that first, then add a surplus.
- How many calories should a runner eat to gain weight?
- Start from maintenance, your everyday needs plus the cost of your runs, and add about 300 to 500 calories a day, the NHS range for gradual gain. The calculator above does the math.
- Do I have to run less to gain weight?
- Not necessarily. First eat enough to cover your mileage plus a surplus, and add strength training. If you cannot eat that much, talk with your coach or a sports dietitian.
- How much protein does a runner need to gain weight?
- The NIH Office of Dietary Supplements puts athletes' needs at 1.2 to 2.0 grams of protein per kilogram of body weight a day. For a 150-pound (68 kg) runner that is about 82 to 136 grams a day.
- What should runners eat to gain weight?
- Energy-dense foods that also fuel training: rice, pasta, bagels, oats, potatoes, full-fat dairy, nut butters, nuts, dried fruit and olive oil, in smaller meals more often.
- Can triathletes use this calculator?
- For the running part, yes. Add cycling and swimming separately; the Compendium lists those activities too, and a sports dietitian can combine them into one target.
Keep reading
References
Sources: National Academies: Dietary Reference Intakes for Energy (2023) · Compendium of Physical Activities: Running · Herrmann et al., 2024 Adult Compendium of Physical Activities · NIH ODS: Dietary Supplements for Exercise and Athletic Performance · IOC consensus statement on REDs (2023) · ACSM Joint Position Statement: Nutrition and Athletic Performance · NHS: Healthy ways to gain weight · Physical Activity Guidelines for Americans · Dietary Guidelines for Americans, 2025 to 2030 · CDC: Low-Energy-Dense Foods and Weight Management · USDA FoodData Central.