Will Losing Weight Make You Faster? What Runners Should Know

Have you ever thought: Would I be faster if I lost a few pounds?

Many runners chase the idea of a “race weight,”  the body weight where performance feels easiest and fastest. And while body weight can influence running performance, the relationship is more complicated than simply getting lighter. 

Race weight is the body weight where a runner feels strong, well-fueled, and able to perform at their best. Done correctly, reaching a healthy race weight can help performance. Done incorrectly, it can sabotage your training and leave you slower and fatigued. Here’s how to know the difference.

Does Race Weight Actually Improve Performance?

If you have excess pounds to shed, losing weight and achieving a healthy, athletic weight can help performance. Studies have shown that you can see improvements around 2 seconds per mile per pound of body weight. A runner carrying an extra 8–10 pounds of body fat might see noticeable improvements in pace once that weight is lost.

When Losing Weight Helps, and When It Doesn’t

An important note: losing weight to run faster only works if you have excess non-functional weight (bodyfat as opposed to lean tissue). If you’re already at a healthy weight with a low body fat percentage, losing a few more pounds shouldn’t be a priority as it’s unlikely to lead to any performance improvements and also risks negative health effects. A runner already lean and training hard may actually slow down if they try to lose more.

Finding Your Ideal Race Weight

So how do you know if you actually have weight to lose? Race weight is not a one-size fits all, even for those of the same height. It will vary based on body type and energy needs. The best way to determine if you have extra weight to lose would be to get a body fat measurement (either caliper method or DEXA scan are best). The optimal range for endurance athletes is 6-13% for men and 14-20% for women. This is a good place to start, but keep in mind, lower is not always better. Some athletes may perform better in the higher ranges than other athletes.

Losing Weight Without Hurting Your Training

If you have determined that you have excess bodyfat to lose, you want to approach it carefully during your running training. It is best to try and achieve weight loss slow and steady. A safe goal is losing around ½ pound per week, which is about a 200-300 calorie deficit per day.

Running burns a lot of calories, so underfueling can quickly hurt performance. Spread your calories throughout the day and make sure you are fueling:

• Before your runs
• During long runs (90+ minutes)
• Within 30–60 minutes after running

For more help on general running nutrition, read Nutrition Basics for Runners.

Fueling Matters More Than the Scale

While maintaining a small calorie deficit (200-300 calories per day), don’t skimp on the nutrients your body needs the most to fuel and rebuild from your running and training. Keep your protein intake at 1.6-2.2g/kg of bodyweight, and keep carbohydrate intake at 4-6 g/kg of bodyweight. Create your calorie deficit primarily by reducing fat intake slightly, while keeping protein and carbohydrates high enough to support training.

Tip: focus mostly on whole, unprocessed foods to give yourself proper nutrients.

Race Weight Isn’t Year-Round Weight

Sometimes during heavy training loads, you may hit a lower “race weight” naturally with the increased training. This weight should only be maintained for the weeks leading up to the goal race. Once your race has passed and your training load returns to a maintenance level, it is healthy and normal to gain a little bit of weight.

The Best Race Weight Is the One That Feels Strong

While achieving a lean, athletic race weight can help shave seconds off the clock, always be mindful of keeping your body in a healthy range – which can look different for everyone. If you feel tired, or feel your performance slipping with weight loss, that may not be the right weight for you. Instead of focusing on a specific number on the scale, runners should focus on good nutrition and how their body feels and performs.

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