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Body Composition and Running: What Changes Can You Expect?

Posted on April 19 2017

Special guest post by Jessica Thiefels, owner of Honest Body Fitness (bio below)

Running is a great way to attain a strong and lean body, burning around 600 calories per hour efficiently and effectively. But what does “strong” and “lean” really mean? 

When you start a running program, or simply pick it up as a new way to stay fit, your body goes through a variety of changes, specifically with fat, muscle, and metabolism. If you want to know what that might look like on you, you’ve come to the right place.

Find out what body composition changes you can expect, along with tips for maximizing the results to become your strongest, leanest self.


Fat Loss

Losing weight, at the base level, is a matter of tipping the scales on energy in and energy out. When you begin a running program, you start expending more energy on a regular basis. If you keep your energy-in (total calories eaten) relatively the same, science says you’ll start to lose fat.


Muscle Gain 

Not every runner gains a note-worthy amount of muscle mass, but that doesn’t mean you can’t. “Although skeletal muscle hypertrophy after aerobic exercise training is not ubiquitous, nearly all studies examining muscle mass since 2005, have reported skeletal muscle hypertrophy in the muscle group(s) most utilized during exercise,” according to Skeletal Muscle Hypertrophy After Exercise.

When running, you use a very specific set of muscles each time, including your core and low back (stabilizers), calves, quads and hamstrings. As such, these are the muscles where you’ll see the most change in strength and size.



One of the best parts about becoming a regular runner is that your body starts burning more calories for you. “The main benefit to running … is that it is sufficiently high intensity to burn a greater number of calories, while stimulating the metabolic rate for a longer period afterward,” says David Robson, owner of Elite Physique Training Studio. 

Stimulation of your metabolic rate leads to an uptick in your resting metabolism. This chain of events occurs thanks to both increased muscle mass and higher energy demands on your body.

How to Increase Body Composition Changes

At a certain point, your body becomes accustomed to the same distance, speed and terrain. Because this makes it less strenuous for your body, your body stops changing and begins to maintain.

If you’ve noticed your body plateauing, and are no longer losing fat or weight or gaining muscle, boost your body composition changes with the following tips:


1. Track Your Heart Rate

Heart rate is one way to track and improve fat and weight loss and boost muscle building on a running program. “Too often, individuals train at too high of a heart rate, too frequently. Combine this with improper nutrition, and this can create catabolism (muscle breakdown),” explains Dr. Rick Kattouf, best selling author and fitness and nutrition expert.

The goal is to work in your fat-burning zone, which is 60 to 70 percent of your max heart rate. Use this Max Heart Rate Calculator to find yours before your next run.

To make sure you’re staying within this zone during runs, use a simple fitness tracker. You can get one for as low as $45 that tracks your steps, heart rate and more, according to a 2016 pricing analysis. Tracking during your run will keep you accountable to staying in this zone, allowing you to scorch fat and build muscle.


2. Eat the Right Foods (And the Right Amount)

First and foremost, you need to be eating enough food. If you don’t replace the calories that are burned when running, your muscles won’t be able to grow. John Sifferman, Health-First Fitness Coach explains how to calculate the extra calories you need: 

“Let’s say you need 2500 calories per day to maintain your weight. That’s your Total Daily Energy Expenditure (TDEE). If that’s the case, you’d want to eat somewhere between 2600-2800, which will be roughly a 5 to 15 percent surplus. That slight surplus will be just enough to get your body into anabolic mode to enable muscle building.”

Secondly, you need to reduce your fat and boost your protein. For protein, focus on getting a minimum of .8 grams per pound of body weight. Eat lean, whole protein sources, like chicken, turkey, beans, fish and some nuts. Don’t eat too many nuts, because the fat adds up quickly; to maximize body composition, you want to reduce your fat intake a bit. 

Owen Anderson, Ph. D recommends, “A reasonable recommendation is for fat to make up 15 to 20 percent of daily energy intake, with omega-3 and monounsaturated fats making up the bulk of this lipid consumption.”


3. Run Harder, Longer and More Often

Simply jogging for 20 minutes just 2 or 3 days a week will likely not help you build a notable amount of muscle. To maximize this, the goal is to keep the intensity high (70 to 80 percent HRR), the duration to 30 to 45 minutes, and frequency at 4 to 5 days per week.

This helps you to achieve “a large number of muscle contractions that places a high-volume, low-load on skeletal muscle compared to traditional hypertrophic resistance exercise programs,” explain the authors of the previous hypertrophy article.


Now it’s time to get excited for the body composition changes that are in your future. When you get into a regular routine and become a great runner, you’ll feel lean and strong, and ready to maximize your efforts for even greater results.



BIO: Jessica Thiefels has been writing for more than ten years and is an ACE Certified Personal Trainer, NASM Certified Fitness Nutrition specialist, and the owner of her own personal training business, Honest Body Fitness in San Diego. She offers both in-person and online personal training. She’s also written for Shape, Reader’s Digest, AARP, Snap Fitness, 24 Hour Fitness and more. Follow her on TwitterFacebook and Instagram for health articles, workouts tips and more.


  • Gary Mickel: June 04, 2017

    I have watched Physiclo since introduced on Kickstarter I would love to have a pair of tights and Shorts to run or walk in & I am trying to refer friends to give them the $15 off so I can get that as well and afford better buying them since I am retired and on disability for back problems and just had surgery almost 7 months ago a double fusion & now I need to rebuild the strength lost in that time although I continue to try to walk/run with vertigo that was caused by spinal cord damage that was repaired in a 9 hour surgery in November 2016. These both tights and shorts would help me immensely but on my budget they are hard to afford without the discounts 15% or $15 off them.

  • Frank from Physiclo: April 21, 2017

    @Candace, we’re restocking soon, and we’ll have your pre-order shipped out early next week! Thanks so much for your patience :)

  • Candace Davis : April 21, 2017

    I have not received my order, and the pay pal has already sent payment to you.

  • Frank from Physiclo: April 20, 2017

    @Denise, sorry for the wait! We’re restocking on Monday, so all pre-orders will be fulfilled early next week!

  • Denise: April 19, 2017

    I have not received the oants yet!

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