Everything You Need to Know About Fitness — and Why It’s About Way More Than Hitting the Gym

Medically Reviewed

What does it mean to be fit? Finding a discrete definition is somewhat difficult. According to the dictionary, fitness means: “the quality or state of being fit." (1) (The definition of “fit” is: “sound physically and mentally.") (2) If you find those words somewhat vague, you’re not alone.

And that’s sort of the point, according to exercise experts. Fitness doesn’t have to mean that you’re an ultra-marathoner or that you can perform one pull-up or one hundred. Fitness can mean different things for different people.

“For me, fitness is first and foremost about feeling good and being able to move without pain,” says the certified strength and conditioning specialist Grayson Wickham, a New YorkCity–based physical therapist and the founder of Movement Vault, a mobility and movement company. He explains that true fitness is about feeling healthy and being in sufficient shape to do the activities you want to do and live the lifestyle you want to live. Can you play with your kids orgrandkids? If hiking the Inca Trail is on your bucket list, can you do it? Do you feel good after a day spent gardening? Are you able to climb all the necessary the stairs in your life without getting winded or having to take a break?

Michael Jonesco, DO, an assistant professor of internal and sports medicine at the Ohio State University Wexner Medical Center in Columbus, agrees. “Since medical school, I've learned that physical fitness is simply defined as your body's ability to perform tasks. Nowadays, there are more tools available than ever for fitness enthusiasts to track, measure, and follow.”

For example, you’ve got body mass index (BMI), resting heart rate, body fat percentage, VO2 max, 5K or marathon personal records (PRs), 100-meter-dash times, and bench-press maxes, he says. “These are all objective measures we use to gauge progress (or measure ourselves against the guy or girl on the metaphorical squat rack or treadmill next to us).”

RELATED: What BMI Has to Do With Health and Wellness

But physical fitness should not solely be measured with any one of these or other tests or evaluations, he adds. It's much more complex. You wouldn’t, for instance, use one factor (such as blood pressure) to measure someone’s overall health, Dr. Jonesco says. Blood pressure is a useful test to monitor for cardiovascular disease, but it doesn't indicate whether or not someone has cancer or dementia.

“Physical fitness should be considered a balance of many of the aforementioned measures, but also many more intangible measures, too,” Jonesco explains, including “your outlook on not just your body, but your attitude toward your own health and wellness.”

RELATED: Women’s Wellness Report 2017: What Factors Keep Us Well?

Traditionally, experts have defined five key components of physical fitness: body composition (the relative proportion of fat and fat-free tissue in the body), cardiorespiratory or aerobic fitness, flexibility, muscular strength, and muscular endurance, according to the American College of Sports Medicine (3). But you can’t discount the impact of nutrition, sleep, and mental and emotional health on fitness either, says Jeffrey E. Oken, MD, deputy chief of staff at the Edward Hines Jr. VA Hospital in Hines, Illinois.

That means looking fit doesn’t mean you actually are.

“Some individuals obsess on their physical appearance and numbers but are motivated by low self-esteem and criticize the flaws of their physical appearance. Some sacrifice rest and sleep in order to achieve further success but, in turn, drive their body into illness or burnout,” Jonesco says. “Fitness is a truly a spectrum of physical well-being that must balance our physical and emotional motivations.”

When all of the components of fitness are balanced, physically and mentally, we get the most benefit.

RELATED: Here’s Everything You Need to Know About How to Be Physically Fit and Make Exercise Part of Your Routine

Read on to learn all about why being fit is such an important part of your health and well-being, now and throughout your entire life.

Being Fit Boosts Energy, Mood, Sleep, and Your Immune System

Because fitness is the state of being physically able to live the happy, fulfilling life you want — the first and most obvious payoff of achieving fitness is high quality of life.

Research links fitness to:

  • Increased energy levels (4)
  • Better work-life balance, according to a study in the November/December issue of the journal Human Resource Management (5)
  • Stronger immunity (6)
  • Sounder sleep (7)

Some research suggests that increasing your fitness through exercise may help mild to moderate depression just as much as medication. (8)

Physical activity is also connected to better focus and productivity. A study published in the May 2015 issue of the journal Psychophysiology suggests this is because exercise increases the flow of blood and oxygen to the brain. (9)

The mental health and emotional health benefits of physical fitness are some of the most important ones — and often have the biggest effect on someone’s quality of life, Jonesco says. “The satisfaction of pushing your body and seeing it respond breeds not only a stronger, faster, leaner body, but a more peaceful, satisfied, and confident mind.” When you’re physically fit, you know firsthand what you can accomplish when you put your mind to it, and you become empowered to hit your personal, career, and relationship goals in a way you wouldn’t otherwise.

What’s more, you can’t deny the impact of fitness on helping people achieve (and maintain) healthier weights. (10) That’s because increasing your fitness level through physical activity not only burns calories, it builds metabolically active muscle. And the more strong, healthy muscle you have, the more calories you burn every day at rest, Wickham says. A fitter body equals higher metabolism equals healthier weight.

Learn More About the Ways That Being Fit Boosts Energy and Mood

Exercise and Sleep Have a Very Intimate Relationship. Here’s How They Both Play a Role in Overall Fitness

Think about it this way: Even a marathon runner who fits in multiple strength-training workouts per week can throw off their fitness by eating a diet of highly processed foods that are low in nutrients and high in saturated fats and sugars. Similarly, someone with stellar workout and diet habits can sidetrack their fitness by not logging a consistently healthy amount of sleep each night.

RELATED: What Happens to Your Mind and Body When You Skip Sleep

Sleep is incredibly important to keeping your body functioning optimally, explains W. Christopher Winter, MD, the president of Charlottesville Neurology and Sleep Medicine in Virginia and the author of The Sleep Solution: Why Your Sleep Is Broken and How to Fix It. Slacking when it comes to sleep can undermine your fitness goals.

RELATED: How Much Sleep You Need Every Night

The benefits of keeping both sleep and physical activity in check? Staying active helps your sleep, and logging the seven to nine hours of sleep per night recommended by the National Sleep Foundation helps you maintain the energy you need to actually stick to your workout goals and stay active (11).

Learn More About the Intimate Relationship Between Fitness and Sleep

Staying Fit Benefits Long-Term Health in Big Ways

While the immediate gratification of fitness is awesome, you can’t forget that you may not notice many of the greatest benefits of fitness for years, or even decades. (Patience, patience.)

For example, studies consistently link physical fitness with improved longevity. (12) According to a study published in the October 2013 issue of Lancet Oncology, when your body becomes fitter, it lengthens its chromosomes’ protective caps, called telomeres. (13) Thosetelomeres are in charge of determining how quickly your cells age. That means keeping them in top shape (being fit) can help lengthen your life span.

What’s more, improved fitness drastically reduces the risk of chronic diseases that develop over the course of many years, such as heart disease, type 2 diabetes, and even cancer. And a rapidly growing body of research suggests being fit may help prevent dementia, too. (14) “The one thing that will help prevent almost any type of disease is fitness,” Wickham says.

And in addition to all those benefits, fitness can help you live better and stronger through the years. One out of every three adults age 60 and older suffers from severe levels of muscle loss, called sarcopenia, according to data published in the November 2014 issue of the journal Age and Ageing. (15) Additional research shows that the condition contributes to fat gain, low mobility and function, falls, and even death in older adults, but that exercise can help prevent this effect of aging. (16)

“The explanation really comes down to evolution. Our bodies and genes have evolved to be active and mobile,” Wickham explains. “When you give your body what it needs, it rewards you by being its best.”

Learn More About the Amazing Ways Being Fit Boosts Your Health

Why Being Fit Helps With Chronic Disease Management

Getting regular exercise and keeping your body fit helps lower your risk of chronic problems, like heart disease, cancer, and type 2 diabetes. But what about the chronic problems that do show up? Across the board, physical activity and maintaining fitness usually helps.

You may need to modify your exercise routines or take specific precautions depending on your symptoms, according to information from the Mayo Clinic. (17) (Be sure to check with your doctor before starting a new exercise program and discuss any limitations or modifications you should be aware of.)

But for most people, regular activity can help with such conditions as heart disease, diabetes, asthma, back pain, arthritis, and cancer. And maintaining fitness also helps ward off additional conditions you might otherwise be at risk for. (17)

Learn More About Why Being Fit Helps With Chronic Disease Management

Here’s How Much Physical Activity You Should Be Doing

So how do you make fitness part of your overall lifestyle — and reach your own individual fitness goals? Jonesco recommends starting with meeting the federal guidelines for physical activity.

The U.S. Department of Health and Human Services (HHS) recommends that, for general health, adults should aim for 150 to 300 minutes of moderate physical activity or 75 to 150 minutes of vigorous-intensity aerobic physical activity each week. (18). The HHS guidelines also note that doing more than those quantities of activity will yield additional health benefits. And the guidelines recommend that adults do muscle-strengthening exercises (of moderate or greater intensity) for all the major muscle groups at least two days per week.

Research shows that aerobic exercise is important for cardiovascular health (19). (The intensity you choose should be based on your current fitness level and your doctor’s recommendations.) Examples include walking, running, cycling, and swimming.

And other research shows that strength training provides other important health benefits. A study published in the February 2015 issue of the journal Obesity shows that, compared with cardiovascular exercise, resistance exercise is more effective at preventing the accumulation of abdominal (visceral) fat, which is linked to the development of chronic diseases, including heart disease, type 2 diabetes, and cancer (20). And a 2019 study published in the journal Medicine & Science in Sports & Exercise found that individuals who regularly strength trained had a lower risk of heart attack, stroke, or death related to heart disease compared with people who didn’t strength train — and those benefits were independent of whether or not they regularly did aerobic exercise. (21)

These strength workouts should target one or all of the body’s basic muscle groups, such as the legs, core, back, hips, chest, or arms. Lifting weights, working with resistance bands, or performing body-weight exercises are all good options and should be used to match, and improve, your current fitness level.

RELATED: The Best Exercises for Stronger Abs and Core Muscles

RELATED: The Best Exercises to Strengthen the Muscles of the Back

“There's no shame in building to these guidelines over a month or so,” Jonesco notes. And do realize that the guidelines leave a lot of room for personalization. This is on purpose because the most important aspect of a workout is keeping it up. “You must enjoy a given activity if you expect to continue to be motivated to do it on a regular basis,” he says. If you don’t like running, that’s okay. Try swimming or take an indoor cycling class.

And importantly, the HHS physical activity guidelines stress that some movement is better than none, and no matter how short a spurt of activity is, it can still count toward your weekly goals. The bottom line is that adults should be moving more and sitting less over the course of their days.

That may sound overwhelming but not if you expand how you think of exercise beyond time spent in the gym, Wickham says. Instead, think about all the movement you do as exercise. “Even people who are exercising regularly often aren’t moving throughout the day,” he says.

A study from researchers at Northwestern University found that women who meet current activity guidelines sit just as much as those who don’t work out (22).

Instead of focusing on getting all of your day’s (or week’s) activity in one go, Wickham advises integrating movement and activity into your day-to-day life. Try breaking up long stints of sitting with any activity that takes your body through its full range of motion, feels good, and helps you dive back into whatever else you were doing with renewed energy.

And don’t forget about stretching. While experts are currently debating the benefit of stretching after a workout (stretching before exercise is no longer advised), stretching throughout the day is a great way to ease tight muscles, relieve tension, and promote the flexibility you need to perform both in the gym and in life, according to Wickham.

Again, fitness is all about giving your body what it needs to thrive. Just make sure to listen.

Learn More About How Much Exercise You Actually Need

Resources We Love

Favorite Orgs for Essential Fitness Info

American Council on Exercise (ACE)

ACE is a nonprofit exercise professional and health-coaching certification organization. The group’s mission is to educate exercise professionals and coaches, and connect individuals to those professionals.

American Heart Association (AHA)

AHA was founded in 1924 with the mission of fighting heart disease and stroke. Today, the nonprofit’s mission statement is: “To be a relentless force for a world of longer, healthier lives.” The organization funds research, advocates for efforts to improve health, and helps provide health services and information to those who need it. You’ll find information on the site about physical activity, nutrition, healthy lifestyle habits, and how to balance it all.

Favorite Online Community for Fitness

Health at Every Size

Health at Every Size describes itself as a movement supporting people of all sizes to adopt healthy behaviors. On the site you’ll find a blog, podcasts, books, online and in-person support groups, and more to help everyone meet their fitness goals.

Favorite Fitness Podcasts


Hurdle, created and produced by New York City–based editor and personal trainer Emily Abbate, tells the stories of inspirational people who have gotten where they are today — at least in part — due to finding a fitness or wellness practice. Check it out for lots of fitness inspiration.

The Strength Running Podcast

Yes, this podcast is about running, but it’s also about how to maintain other aspects of your fitness if you are a runner. Episodes cover nutrition, running while vegetarian, coaching, dealing with failure, injury prevention, supplement use, and more.

Favorite Instagrammers Who'll Inspire Fitness


Holly Davidson is a personal trainer with expertise in yoga, high-intensity interval training, suspension training, kettlebells, boxing, mobility, and weight loss and dietary management. She’s written two books on health and fitness. She claims food is an integral part of a healthy lifestyle, and nutrition is an important component of any training program. And we couldn’t be more in love with her message: “I want you to fall in love with being active,” she writes on her website. Follow her on Instagram for reminders of how to keep fitness fun.


Joe Wicks is a personal trainer with a subscription online fitness and nutrition program to get stronger, leaner, and healthier. Follow him on Instagram, where he shares inspiring success stories, healthy eating options, and how stays fit. His Instagram summary pretty much sums up what to expect: “On a mission to inspire one new person every day to exercise and cook a healthy meal.”


Kirra Michel is a New York City–based personal trainer, health coach, and yoga instructor. You’ll find more about her yoga classes, workshops, and guided meditations on her website. On Instagram, follow her motivational updates about yoga, staying active, and staying mentally well.

Editorial Sources and Fact-Checking

  1. Fitness. Merriam-Webster.
  2. Fit. Merriam-Webster.
  3. ACSM's Health-Related Physical Fitness Assessment Manual. American College of Sports Medicine.
  4. Puerts TW, et al. A Randomized Controlled Trial of the Effect of Aerobic Exercise Training on Feelings of Energy and Fatigue in Sedentary Young Adults With Persistent Fatigue. Psychotherapy & Psychosomatics. March 2008.
  5. Clayton RW, et al. Exercise as a Means of Reducing Perceptions of Work-Family Conflict: A Test of the Roles of Self-Efficacy and Psychological Strain. Human Resource Management. November/December 2015.
  6. Nieman DC, et al. Upper Respiratory Tract Infection Is Reduced in Physically Fit and Active Adults. British Journal of Sports Medicine. September 2011.
  7. Loprinzi PD, et al. Association Between Objectively Measured Physical Activity and Sleep, NHANES 2005–2006. Mental Health and Physical Activity. December 2011.
  8. Carek PJ, et al. Exercise for the Treatment of Depression and Anxiety. The International Journal of Psychiatry in Medicine. January 2011.
  9. Cameron TA, et al. Near-Infrared Spectroscopy Reveals Link Between Chronic Physical Activity and Anterior Frontal Oxygenated Hemoglobin in Healthy Young Women. Psychophysiology. May 2015.
  10. Foster-Schubert KE, et al. Effect of Diet and Exercise, Alone or Combined, on Weight and Body Composition in Overweight-to-Obese Postmenopausal Women. Obesity. August 2012.
  11. Hirshkowitz M, et al. National Sleep Foundation’s Sleep Time Duration Recommendations: Methodology and Results Summary. Sleep Health: Journal of the National Sleep Foundation. March 2015.
  12. Chakravarty EF, et al. Reduced Disability and Mortality Among Aging Runners: A 21-Year Longitudinal Study. Archives of Internal Medicine. August 2008.
  13. Ornish D, et al. Effect of Comprehensive Lifestyle Changes on Telomerase Activity and Telomere Length in Men With Biopsy-Proven Low-Risk Prostate Cancer: Five-Year Follow-Up of a Descriptive Pilot Study. The Lancet Oncology. October 2013.
  14. Ahlskog JE, et al. Physical Exercise as a Preventive or Disease-Modifying Treatment of Dementia and Brain Aging. Mayo Clinic Proceedings. September 2011.
  15. Cruz-Jentoft AJ, et al. Prevalence of and Interventions for Sarcopenia in Aging Adults: A Systematic Review. Report of the International Sarcopenia Initiative (EWGSOP and IWGS). Age and Ageing. November 2014.
  16. Roubenoff R. Sarcopenia: Effects on Body Composition and Function. The Journals of Gerontology: Series A. November 2003.
  17. Exercise and Chronic Disease: Get the Facts. Mayo Clinic. December 18, 2018.
  18. Physical Activity Guidelines for Americans: Second Edition. U.S. Department of Health and Human Services. 2018.
  19. Bateman LA, et al. Comparison of Aerobic Versus Resistance Exercise Training Effects on Metabolic Syndrome (From the Studies of a Targeted Risk Reduction Intervention Through Defined Exercise — STRRIDE-AT/RT). The American Journal of Cardiology. September 2011.
  20. Mekary RA, et al. Weight Training, Aerobic Physical Activities, and Long-Term Waist Circumference Change in Men. Obesity. February 2015.
  21. Liu Y, et al. Associations of Resistance Exercise With Cardiovascular Disease Morbidity and Mortality. Medicine & Science in Sports & Exercise. March 2019.
  22. Craft LL, et al. Evidence That Women Meeting Physical Activity Guidelines Do Not Sit Less: An Observational Inclinometry Study. International Journal of Behavioral Nutrition and Physical Activity. 2012.
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