The Effects of Running on Body Composition

Running is a widely favored activity for improving body composition, but how does it truly affect fat and muscle? Can it lead to muscle loss, and how much running is necessary to see results? Let’s explore.

Does Running Cause Muscle Loss?

A detailed study on ultra-marathoners participating in the Transeurope Footrace—where runners covered 2,787 miles over several weeks—provides insight. Participants lost around 40% of their body fat mass but only 1.2% of lean tissue, with most muscle loss occurring in the legs. This was linked to severe caloric deficits and inadequate recovery for their fatigued muscles.

In contrast, moderate running has been shown to enhance muscle mass, especially in beginners. It can even counteract age-related muscle decline. However, excessive training without proper nutrition can lead to muscle loss. By maintaining a balanced diet plan, most runners can avoid this issue and preserve muscle while improving fitness.

Does Running Burn Fat?

Running is one of the most effective ways to burn calories and reduce body fat. A 12-week recreational running program studied in young males demonstrated an average fat loss of 11 pounds, with participants maintaining their fat-free mass.

Interestingly, a similar program involving soccer—known for short bursts of intense activity—produced comparable results. This indicates that both steady-state running and high-intensity, intermittent activity can significantly improve body composition by reducing body fat percentage.

Endurance Running vs. Sprinting

The debate between long-distance running and sprinting often focuses on their respective benefits. Sprinters argue that high-intensity workouts trigger a metabolic afterburn effect, while distance runners highlight the calorie-burning advantage of extended sessions.

A study comparing endurance and sprinting programs over 12 weeks found that both approaches reduced visceral fat and improved body composition. There were no significant differences in fat loss or half-marathon performance between the two groups.

Conclusion

Both endurance running and sprinting offer meaningful benefits for body composition and overall health. Whether you prefer long-distance jogging or high-intensity sprints, choose the style that aligns with your interests and fitness goals. With consistency and proper fueling, running can help you achieve a leaner, healthier body.