Does Weight Loss Make You Run Faster?


Weight is a touchy subject in any type of fitness… Or in general, really! Many of us exercise at least partly with weight in mind, whether to maintain a healthy weight or shed some extra pounds.

But if you’re serious about performance, another question comes into play—does weight loss make you run faster? It makes sense that the lighter you are, the quicker you’ll move, but it’s a little more complicated when you look deeper into it.

Let’s see how your weight affects your running speed and how to lose weight correctly if you want to become lighter and faster.

How Does Weight Affect Running Speed?

Do you remember learning physics? One handy equation tells us that weight is important when it comes to speed:

  • Force = mass x acceleration

This means that the more mass you have, the more force is needed to maintain the same acceleration (speed). In other words, the more you weigh, the harder you must work to be fast!

But it’s more detailed than just that—it’s more about body composition than how much you weigh.

For example, a person who weighs 200 pounds but has 30 percent body fat is going to find it much harder to run fast than someone who weighs 200 pounds but has only 12 percent body fat.

The more muscle you have, the easier and more powerfully you can push yourself forward as you run. You’ll be able to expend more power on your toe-off and push forward harder thanks to more developed quad and glute muscles.

So while weight is important in a way, ultimately, it’s more about body composition than it is about how much you weigh.

How Much Faster Can You Run If You Lose Weight?

A study from 1978 indicated that a 5 percent increase in body weight resulted in running 89 meters less over 12 minutes of running. This works out to increase your mile time by 1.4 seconds for every mile you run.

This might not seem like a lot, but over time and distance, it can significantly change your performance. Put on 5 percent body fat, and you’ll add 14 seconds to your 10-mile race time—and that’s the best-case scenario.

Work this in reverse, and if you lose 5 percent body fat, you can expect to increase your speed by at least 1.4 seconds per mile, possibly up to 3 seconds per mile. Remember that this means losing 5 percent of fat, not muscle!

Your Ideal Racing Weight

It’s hard to say the ideal racing weight, as it’s subjective. Every person is different, so you may need to experiment with this and see what feels best for you.

The lowest body fat percentage they’ve achieved is ideal for most people. For example, if you’ve been down to 15 percent body fat, that will be the best racing shape you’ve ever been in.

But that doesn’t necessarily mean that going lower than that will increase your performance. If losing more body fat triggers a spate of poor performance, take note—that’s where your ideal racing weight is.

In some cases, losing weight means your body isn’t getting enough nutrients to stay strong enough for optimum performance.

Don’t assume that lighter is always better. If you’re already lean, you have less weight to play with, so you must be more careful about how much you lose.

Training Weight vs. Racing Weight

Serious runners often refer to their “training weight” versus their “racing weight”. Your training weight is the weight you want to maintain for most of the year and the weight you’re comfortable training and still see progress.

For the last 4 to 6 weeks before a race, elite runners may slim down to reach their “racing weight”. This weight is not necessarily sustainable over long periods, but slimming down does help them to be a little lighter and faster on race day.

If you’re a recreational runner, you can run at your training weight, and you should still be able to perform well.

The Best Way to Lose Weight

While losing weight can help you run faster, there is a right and wrong way to do it. You want to lose fat and not muscle; in fact, putting on some more muscle can actually help to speed up the fat-burning process.

Follow these tips and tricks to lose weight quickly and safely, while adding some muscle at the same time.

Do Resistance Training

Muscle is a “metabolically-active” tissue that requires energy to maintain. Having more muscle doesn’t mean you’re going to burn a huge amount more fat, but it can make a significant difference over time.

Evidence also suggests that your body continues to burn fat for longer after an intense resistance training session than after cardio. So you’ll get a sustained calorie burn effect, helping you to lose weight faster over time.

But having more muscle will also help you to perform better when you run, as you’ll be able to power yourself forward more powerfully. Doing three to four resistance training sessions a week will significantly affect your body composition.

Don’t Overdo It On Cardio

While it’s true that you can burn more calories in a short HIIT session than in a longer weight training session, too much cardio can easily lead to overtraining and hamper muscle growth.

Three to four cardio sessions per week are usually enough to lose weight safely if you’re in a calorie deficit. If you’re running three to four times a week, that’s enough!

Work Out Your Basal Metabolic Rate

A BMR calculator will help you find your basal metabolic rate, the energy you use daily to survive and perform your bodily functions like breathing and digesting food.

If you can work this out, you have a starting point for figuring out how many calories you should eat to lose weight. To lose weight, you need to eat fewer calories than you burn every day.

A calorie deficit of 20 to 25 percent is a good deficit to lose weight safely. For example, if your BMR is 1200 calories and you’re burning 300 calories during exercise, you’re burning 1500 calories daily. To be in a 20 percent deficit, you’ll need to eat 1200 calories per day.

If you can remain in a calorie deficit for long enough—8 to 12 weeks before incorporating a deload week—you’ll lose weight effectively and safely.

Eat A Healthy Diet

It’s difficult to reach your weight loss goals without paying attention to your diet. Eating processed foods and sugar will add empty calories to your diet and make weight loss harder.

Maintain a diet of whole, healthy foods. Make sure to eat a balanced diet of lean proteins, healthy carbs, and healthy fats while maintaining your calorie deficit.

Hydrate Throughout the Day

Did you know you can carry between one and five pounds of water weight at any given time? Contrary to logic, the more you drink, the less water your body stores, as it tends to store water weight when dehydrated.

Staying hydrated throughout the day means you’re less likely to hold that pound or more of water weight, keeping you lighter and leaner.

Be Consistent

You can’t lose weight healthily in a few weeks. While you might drop a couple of pounds, you need at least a few months before seeing and feeling the effects properly.

Consistency can be the hardest part of weight loss. But without it, you’ll never reach your goals and maintain your goal weight once you reach it.

Can You Lose Too Much Weight?

There is a point where you can lose too much weight, and then it can negatively impact your performance.

If you don’t have excess pounds to lose but continue to restrict calories and lose weight, your body may not be able to sustain enough energy output for you to perform well.

Extreme fat loss also often includes muscle loss, and a lack of muscle can also negatively impact running performance.

Photo of author


Ben is an avid road and trail runner, and has completed multiple marathons and ultras. A former running store owner, he now shares his knowledge and experience writing these articles.