Skip to Content

How Running Changes Your Body (Most Of It’s Good)

Taking up running will change your life. I mean it. Running isn’t just a way of exercising, it’s joining a community (and not in a scary religious cult type of way).

Yet the questions most would-be runners want answering are “How running changes your body?” and “What does running do for your body?” Most of it’s good. Really good.

  • Running boosts your cardio, helps reduce stress, and lets you sleep well at night.
  • Taking up running is good for your fitness and can help you lose weight.
  • Expect to lose body fat and develop envious calf muscles.

Some people even think we evolved to run. If you’re body-obsessed, or just trying to get in shape, I’m sure you’ll want a few more details such as will my butt look good, is running the best way to get fit, and is there a typical runner’s body?

✅ Most people start running to lose weight… then hopefully fall in love with running. If you’ve tried running before and failed to make it stick, this guide will change your view of running.

This post contains affiliate links. This means I receive a commission if you make a purchase through my links, but this is no additional cost to you. Please read my disclaimer for more information.

how running changes your body

You Will Lose Body Fat

When people want to know what does running do to your body, often what they have in mind is losing weight. It’s simple really, weight loss is about the balance between calories in versus calories out, and running is a great way to burn calories.

In my view, it’s the BEST! You burn nearly double the number of calories compared with walking. Each mile you run burns around 100 calories. There’s no expensive gym membership, most people can run right from their door and all you really need is a good pair of running shoes. Develop a regular running habit and you will lose weight.

There are a few caveats. Running makes you hungry. Did I say hungry? I meant starving! Forget to refuel after a run and the only thing on your mind will be, “I need to eat NOW”. (Beware of HANGRY runners – they need feeding!)

If you’re running to lose weight, this can be a bit tricky. You don’t want to replace all the calories you’ve just burnt by reaching for a big sugary donut! It might be tempting but you’re going to regret it!

Make sure the food you’re eating fits with your weight loss plans. I find filling up on whole-grain carbohydrates, beans, and lentils with lots of fresh fruit and vegetables works best. Get a healthy snack lined up ready to eat just after your run.

If you’re running to lose weight, don’t aim for perfection overnight. Get used to running first. When you’re two to three weeks in and running is becoming a habit, then it’s time to give your diet an overhaul – one small step at a time. Forget seeking a halo – it’s best not to change everything all in one go.

Age, metabolism, conditions such as hypothyroidism, can all make weight loss difficult. Yet we’re a society that eats too much and moves too little – and for most people, a running lifestyle will help. If you’re struggling to lose weight through running, strength-building exercises and high-intensity interval training (HIIT) will boost your metabolism AND do wonders for your speed. Just don’t do too much too soon if you’re a running newbie.

Your runners body

Your Thighs Will Become Toned

Always wanted to get rid of fat at the top of your thighs? Running is the answer. It’s hard to think of any regular runners who don’t have toned thighs.

Running gives your legs a terrific workout. Run regularly and your thigh fat will be history.

how running changes your body
Running will shrink your boobs but to be fair it’s a downside of all weight loss.

Your Boobs Will Shrink

This is a downside. To be fair, it’s a downside to losing weight full stop. Most women, (and men), will lose weight off their chest when they take up running.

You can still have an attractive cleavage. Just make sure you wear a sports bra even if your breasts are small. No one wants saggy boobs!

It’s not a question of looks. Sports bras are essential for female runners to protect the Cooper’s ligaments that support the breasts from stretching. Run without a sports bra and it hurts – big time.


Reading Tips For How Running Changes Your Body

Full of encouragement, this is the book to get if you think you hate running!

Runner’s World is always a good place to start looking for running advice.

7 easy-to-follow running plans. A plan for every goal, big or small.

Run For Your Life will help you discover how to take up running without pain or injury.


You Will Develop Envious Calf Muscles

Best chat up line ever? Walking around a bookstore in Sydney I was asked “How did you get such great calf muscles? You must be a runner!”

Now my calf muscles have been admired by many, but using it as a chat-up line was a first!

Running will build your calf muscles giving you shapely legs.

There is a downside. You will no longer be able to fit into skinny jeans, skinny boots, or anything that requires stick-thin skinny legs. Will it bother you? I doubt it. You’ll be too busy running…

what does running do for your body
Running up hills builds big powerful calf muscles.

Your Arms Will Shrink

This is another downside of losing weight. If you’re running intensely, the muscles you’re not using will slim down. That means no more arm muscles.

There is a way to prevent weedy arms. Combine running with yoga or any other weight-bearing exercise that gives your arms a good workout.

You Will Have The Best Butt Ever

Running doesn’t just tone your legs, it tones everything below the waist. Think stomach muscles of steel and a butt to die for.

When you run you’re really working your gluteal muscles. That means an envious butt without having to hit the gym.

Strengthen your glutes with hill reps
Strengthen your glutes with hill reps for the best butt ever!

You’ll Sleep Better

Physical exercise increases the amount of time in deep sleep and can help with insomnia. The only proviso is to avoid intense activity in the hours before bedtime.

(No cramming in a run late at night because you forgot to go earlier – set your alarm for an early morning run instead).

Run earlier in the day and feel the benefits when it’s time to get some shut-eye. Sleep soundly and awaken refreshed.

running helps you sleep better
Running helps you sleep better.

You’ll Feel Terrific

Running just makes you feel great. It gives you energy and builds confidence making you more outgoing. However, when it comes to “How running changes your body” it’s about more than just the physical side.

It’s a wonderful way of making friends and you’ll find yourself enjoying your journey towards becoming a fitter, healthier person.

Being able to move better, run to catch a bus, get the maximum use out of your body, just makes you feel terrific.

You’ll Stop Overthinking Everything

The runner’s high isn’t a myth. Running releases endorphins creating a natural high. This way you get to feel good without any side effects.

It could be the endorphins or just the benefits of exercise, but running creates positive outlooks, helps you stop overthinking and sweating the small stuff. Life’s just better when you’re running regularly.


What Does Running Do To Your Body?

If you’re squeamish, look away now. Personally, I start to feel a little faint whenever I read about heart rates and circulation, but I’ll give it a go just for you.

Let’s talk biology. What exactly is running doing to your body?

When You First Start Running

Initially, you’re going to be out of breath and your heart rate shoots up. You’re breathing oxygen into your lungs and your heart is pumping oxygenated blood into your muscles.

You won’t feel great and your stomach can feel a bit weird. It’s busy breaking down energy causing muscle cells to release gas.

Your muscles will start using Adenosine Triphosphate (ATP) for energy. This is an organic compound that provides energy for cells. It’s stored in glycogen within your muscles and your blood, but we only store small amounts in our bodies. As you start to run your body creates more.

This Needs More Oxygen

To create ATP your body needs more oxygen. That’s why you start breathing harder and faster. Your body diverts blood away from anything that’s non-essential, such as your digestion. It’s a reason it’s hard to eat and run.

You’re burning calories, lactic acid builds up in your muscles and your core body temperature rises. That red face occurs as blood is diverted nearer to the skin to be cooled and you’re sweating profusely to try and cool down.

out of breath running
It gets easier! Your body becomes more efficient at getting oxygen to your muscles as you improve your running.

As You Continue Running

If you’re in shape, you’ll breathe, sweat, and convert glucose to ATP. Your body settles into a comfortable cycle.

When you’re new to running, your body is less efficient and lactic acid builds up. Running starts to hurt! It’s a good reason to go easy when you start out as a beginner runner.

What Does Running Do For Your Body?

Couch surfers love criticizing runners. Anything to give them an excuse not to get off their butts and get some exercise! But just like most things in life, there isn’t a straightforward answer to “Is running good for you?”

Are we born to run?

Chris McDougall’s Born To Run book exploded onto the running scene in 2009. Telling the tale of the Tarahumara Indians who run down prey barefoot to survive, ultra runners couldn’t get enough of the story.

Suddenly runners weren’t just lycra-clad freaks but people following their natural instincts. A whole new movement of people running barefoot appeared overnight – not often with the best of outcomes with our soft western feet and dirty city streets.

The idea we’re natural runners is convincing. Young children love to run and will happily run around playing all day long. Sitting all day at school, peer pressure, electronic gadgets… all conspire to produce nations of non-runners.

It can help with major depressive disorders.

Running pumps out mood-enhancing endorphins and endocannabinoids. The legendary runner’s high is real.

Take my word for it or try it out for yourself. No matter how hard you find your run, you’re guaranteed to come back feeling better about yourself.

Is running good for you
Is running good for you?

Is running bad for your knees?

Grannies love to tell you “running will damage your knees” but is this true or is it just a myth?

Science suggests the opposite. There’s no evidence it’s bad for your knees and weight-bearing exercises help protect against osteoporosis.

That doesn’t mean you’ll be immune from knee pain. Runner’s knee, patellar tendinitis, or iliotibial band syndrome are common overuse injuries.

Just like any other sport, it’s important to treat your body with respect: build your running miles slowly and avoid muscle imbalance. Regular yoga is a great way to stay injury-free.

Endurance runners have bigger hearts

No this doesn’t mean they’re more likely to remember Valentine’s Day! Endurance runners can have hearts that are 50% bigger than normal. They can also have wider arteries and slower resting heart rates. Is this all sounds good but it’s also possible excessive running thickens the heart tissue, causing fibrosis or scarring.

So what is excessive and is it really a risk? Medical science fully supports moderate exercise. Running just 5 to 10 minutes a day can make a big improvement to your health, reducing your risk of heart disease. It’s the effect of high volume running that’s inconclusive. What about those runners clocking up ultra-marathons and pushing through 40+ mile weeks? At the moment there are no clear answers.

That doesn’t mean it’s bad for you. Running persistently gives you good cardio and it’s encouraged by your doctor, you just need to be aware of the potential risk of overdoing it. It’s always okay to slow down or walk on those steep hills. Just listen to your body.

Is running good for you?

It’s a resounding yes! Any downsides to running come from over-doing it. If you want a great body, enhance your moods, sleep better at night and benefit from good cardiovascular health, lace up some running shoes.

Is running good for you? It’s a resounding YES!

Your Runners Body

There’s no such thing as “a typical runner’s body”. Ignore any comments from gym fans that running will make you look weedy.

Or get the idea that you can’t lose weight from running just because the guys at the back of your local race are carrying some extra pounds.

Two of the most famous runners in the world are Usain Bolt and Mo Farah. Completely different bodies. The former is all muscle to run fast and the latter has his body dialed for maximum efficiency to run a marathon.

For female equivalents compare the Olympic sprinter Tori Bowie and former World Record marathon runner Paula Radcliffe.

Your runner’s body will be dictated by your build, what you eat, and how you train. However, if you want to build muscle, such as a curvaceous butt, work on your hill reps and speed intervals.

If you want to lose weight, balance running with a healthy diet, and avoid eating excess calories.

Hopefully, you’ll learn to love running for more reasons than how you look. Take it from me, the health and social benefits are immense.


I hope this insight into “how running changes your body” will convert you to take up running. It’s been a big part of my life for years and has taken me on all sorts of adventures. I’d love to hear about yours…

If you're thinking about taking up running and want to know how running changes your body - read on. Most of it's good and you'll feel terrific. #running #fitnesstips
Enjoy this post? I’d love you to share my pin!

Frequently Asked Questions – How Running Changes Your Body

How running changes your body?

Running changes your body by burning body fat and building muscles. Expect to lose fat at the top of your thighs, build stomach muscles of steel, and a butt to die for the weight. When you run you’re really working your gluteal muscles. That means an envious butt without having to hit the gym. Running increasing your strength and endurance plus interval training can boost your metabolism. You’ll lose weight if you combine running with a calorie-controlled diet.

How does running change a woman’s body?

Running is a great way to burn calories and can help with losing body fat. However, if you’re trying to lose weight, you need to combine running with a healthy eating plan. Running will tone your legs and give you a perfect butt. There’s a good chance your boobs will shrink. Running makes you feel terrific. It’s not just a runner’s high, you feel more energetic, it builds confidence, and makes you more outgoing.

Can you get in shape by just running?

Running is excellent cardio and if you combine running with healthy eating you can achieve a high standard of fitness. But running does neglect some muscle groups, especially your arms, so it’s good to add one or two weekly gym workouts, yoga, or HIIT to your training schedule.

What happens to your body when you run every day?

It’s best for most runners to take at least one rest day a week. Beginner runners should run no more than alternate days. Running every day won’t give your body a chance to recover and could lead to injury. Building up to a routine of running just 1 to 2 miles a day is achievable and will have terrific cardio benefits such as a reduced risk of heart disease. Running is a terrific way to get in shape.

Will running 2 miles a day tone my body?

Running 2 miles a day will definitely tone your body. For best results combine running with healthy eating. If you’re a beginner runner don’t jump right into running every day. You need rest days for your body to recover and to reduce the risk of injury.

Does running make you skinny?

Running is an excellent cardio exercise. The intensity of the exercise can mean you burn more calories per minute compared with walking, cycling on the flat, or swimming. Weight loss happens when you use up more calories than you consume. Running can help you lose weight provided you don’t over-eat after your run. You need a calorie deficit to lose weight and running can be a terrific aid to achieve this.

How long does it take for running to change your body?

For real change your running needs to be regular – at least 30 minutes 3 times a week. Suggest also walking/cycling for an extra 2 days a week. With this level of commitment, you will start to notice small changes in 3 to 4 weeks and major changes in 2 to 3 months.

Will running help lose weight?

Yes! Running is one of the best ways of burning calories but unless you’re going to run a very high mileage every week, you also need to watch your diet. (Please don’t start running a high mileage overnight, it’s a good way to get injured. Always build up your weekly mileage slowly – no more than 10% increase per week). Running one mile burns around 100 calories so it’s easy to replace those calories with an after-run treat. Find out more in my post Running For Weight Loss Plan.

Clifford Stanger

Friday 29th of October 2021

I have been running exactly 1 year, started out 256lbs, currently 197lbs. I started out on a track, just getting over plantar faciatis, barely able to run 1 lap. Recently ran my first 10k and got lost as it was in the mountains, I ran an extra mile 7.41 miles to be exact, I couldn't believe it, muscles were depleting but I finished strong, breathing was great, wasn't tired. I am hoping to drop 20 more pounds and goal is to run 30 mile race Called the Elkhorn Crest Trail Run. I am 45 years old, never in my life thought I can do this.

Alison

Saturday 30th of October 2021

Hi Clifford. Thank you for such an inspiring post. That's an amazing journey you've been through in a year! You must be so proud of yourself. Losing so much weight in a year and becoming a runner is really something. I've had a look at the website for the Elkhorn Crest Trail Run. Wow - it looks like a great race! I'm tempted to enter myself! It's going to be a very rough trail for a newbie runner so it will be important to build up your leg strength and ankle strength. This book Run Less Run Faster has some really good advice for building leg strength although I'd go easy on the interval training suggested until you've built up more running strength. I also suggest getting a wobble cushion. Stand on it one leg at a time to build your ankle strength. This is the one I use. I'm rehabbing one of my ankles at the moment and it's really helping. I find a wobble board is too aggressive. Just make sure you build up your mileage slowly and that way you'll avoid injury. You can always hike on some days to build your leg strength with less risk of overtraining. I'd love to hear how you get on!

Jesse Barton

Wednesday 13th of January 2021

Is a 15:29 5k good? I'm only a freshman in high school and I kind of like running. I need some help finding people o run with can you help me?

Alison

Wednesday 13th of January 2021

Hi Jesse, that's an extremely good time for any age group and especially considering how young you are. You would really benefit from having a coach. Speak to your sports staff at school and if they can't help look for a local running club with junior athletics training. You need to find someone who is excited by your potential and can help you improve. It's rare for someone to be running that fast at your age.

mary

Friday 8th of January 2021

I enjoyed reading your article! I always enjoyed jogging when i was younger I just didnt stick with it..having young children at the time, it was difficult to find the time, my knees would hurt after two miles. i know excuses!! anyways, fast forward now, im 55 and was diagnosed with pre diabetes about 5 years ago. i got really serious this past year after a discussion with my doctor when i hit 232 pounds in Sept 2019. He told me its not too late to reverse this diabetes diagnoses. i have always been a yo yo dieter and had a weight issue my entire life. i started walking of course and then i started jogging August 2020. starting with a mile. i remember how excited i was that i could finish a mile. gradually worked my way up to 5 miles a day now. i have lost 60 pounds since Sept 2019 and i have about 6 more pounds to my goal that my doctor and i discussed. I will continue running even after i hit my goal for maintenance. im addicted to jogging now!!! At my doctors appointment in October, my doctor couldnt believe how much weight i had dropped. i am off my diabetic medication and the one thing your article said that sticks to me is...YOU WILL FEEL BETTER. I do! i cannot believe how much better i feel since i started jogging. Thank you!

Alison

Monday 11th of January 2021

Hi Mary, I love your post! Thank you so much for adding your story. It's brilliant that you've been able to reverse your pre-diabetes and get off your meds. It sounds like you've had the best approach to starting running again - walk first, then aim for a mile a day and build it up. Love that you're now running 5 miles a day AND enjoying it so much! You're an inspiration!

Erlan

Saturday 5th of December 2020

When I was furloughed in March from my sales career I was still stressed as if I was still working, eating horribly, and fluctuated between 205-215lbs at 5’6 (large frame) and really didn’t like myself or what I looked like. With work I always used time as an excuse to be active. I decided it was time to change.

I started to go on walks for a few miles and eventually after a few weeks what started as a few miles became 5 and then evolved into 10 miles. I remember being so sore from it and my thighs would always get a rash that I would need to cream up. But as difficult as it was to be patient and fight through the early pains, the “high” from the workout was addictive. All of a sudden my body wasn’t as interested in the crap foods I was accustomed to in the past and I found myself needing to get in the exercise on a daily basis so I could feel good. After 3 or so months my walks evolved into walking/slow jogs and eventually evolved into full-blown jogs. Because I started with walking and had been accustomed to long distances, I basically transformed 10 mile walks into 10-mile jogs and the rest is history. At that point, I got serious about calorie deficit and wanted to get the most bang out of the buck for all my hard work. Once I was able to cut down a significant amount of weight I was happy but not thrilled because I wasn’t firm anywhere. 3 months ago I then added moderate weight training with a trainer and have been doing it once a week and as of December 4th, 2020 I can tell you that now I am solid as a rock and weigh 175lbs which is a 35-40lbs drop and am almost at my goal weight of 165lbs and I feel great every day, am a better person, better single father, and hope that after the pandemic I can find someone special that actually appreciates the “new” me. Running has changed my life. There truly is no better feeling than finding that second gear mid-run and feeling like your legs can go forever.

Alison

Tuesday 8th of December 2020

Hi Erlan, your comment made my day. It's everything I want to encourage with this blog. Love the bit where you mention "suddenly my body wasn't interested in the crap foods I was accustomed to in the past". Although diet is the main driver behind weight loss I always believe it's exercise that gives you the incentive to get in shape and keeps you on track. I sure the new confidence you've found will help you find someone special. Thank you for spreading the word about how great it feels to exercise.

Alex

Friday 4th of December 2020

most of the time