What happens to your body when you don't exercise enough

Some people are born with naturally thin frames and the metabolism that allows them to eat whatever they want and never gain weight. It's tempting for these people to forego exercise altogether in favor of hanging on the couch and watching TV with a friend. As a certified personal trainer, I've had many clients who weren't convinced they actually needed to exercise since they were naturally thin. Exercise does a lot more than help us burn calories to lose weight. In fact, not getting enough exercise can have a pretty significant impact on what's going on in our bodies and the future of our health. What really happens when you don't exercise enough?

You crave unhealthy food

Many people who exercise regularly also eat very healthy diets. While it may seem like this is always due to a conscious choice to be healthier, it turns out that people who are more active actually crave healthy food. This is called the transfer effect and refers to the effect whereby learning new skills and improving in one area of your life automatically triggers a desire for improvements in another. This is great if you're trying to build multiple healthy habits, like exercising and eating healthy.

The problem is, I've seen it work in the reverse for some of my clients as well. When someone falls off the wagon with their exercise routine, it doesn't take their nutrition long to follow. Your body stops craving highly nutritious foods because it no longer needs the extra sustenance. Instead, nutritionally-poor-but-delicious foods like potato chips and chocolate cake become quite enticing. Not only that, but it's a lot easier to eat a bag of chips while you're sitting in front of the TV binge-watching an entire season of your favorite show on Netflix than it is while you're at the gym. Once you start eating junk, you start craving more junk. Wouldn't it be easier to get regular exercise and let your body take care of the cravings itself?

You don't sleep well

Tossing and turning all night, but feel like you still have a ton of restless energy to burn? According to the Centers for Disease Control and Prevention (CDC), one in three American adults is not getting enough sleep. If you're someone who is experiencing sleep problems, you may not be exercising regularly enough.

Regular exercise has been shown to increase total sleep time and leave people feeling more alert and well-rested throughout the day. This has been shown even while controlling for Body Mass Index (BMI), health status, smoking status, and depression. What that means is that the positive effects of exercise on sleep aren't just because people who exercise more tend to have a lower BMI or tend to be healthier overall. Regular exercise can be beneficial for sleep for all of us, even those who suffer from insomnia. When you don't exercise enough, the benefits to sleep aren't as noticeable. While a single day of exercise does produce some small improvements to sleep compared to those who do not exercise, only those who engage in regular exercise see a significant difference in sleep quality. Can't sleep? It may be time to start exercising regularly!

You get winded easily

If you don't exercise regularly, you may find that when you climb a flight of stairs or carry a heavy bag of groceries for more than a few feet, you get out of breath. Regular exercise results in improved cardiovascular (heart and blood vessel) health and pulmonary (lung) health, leading to improved functional exercise capacity and reduced breathlessness in both healthy people and those with chronic lung conditions. This means your body has greater efficiency for taking in and absorbing oxygen, even when your body is fatigued. Without regular exercise, your body is not as efficient at absorbing oxygen when it is under strain. This makes it hard to use the oxygen you're breathing in, so it feels like you aren't taking in enough air. This is why when you return to exercise after time off, it feels like you're back to square one, panting desperately to catch your breath.

By getting enough exercise, you maintain your body's ability to effectively and efficiently get oxygen from the lungs to your heart when you are exerting effort. This isn't just important for making sure you aren't embarrassingly out of breath when you walk up the stairs in public. The process of getting oxygen from the lungs to your heart also determines how much oxygen makes it to your brain and other vital organs. This is why you may get light-headed if you can't catch your breath. We can all agree that getting enough oxygen to the brain is important, right?

Your metabolism slows down

Your metabolism may be great right now, but metabolism naturally slows for everyone as we age. One great way to offset these changes in metabolism is to get more exercise, including both cardiovascular and resistance training, like lifting weights. Research has shown that exercise helps increase a person's Resting Metabolic Rate (RMR), which is the rate at which your metabolism functions when you are not exercising or otherwise active. While RMR is affected by other factors as well, including a person's body weight and muscle mass, increases in RMR from regular exercise are valuable.

On the other hand, when you don't get enough exercise, your under-used muscles gradually shrink (thanks to a phenomenon called sarcopenia that causes muscle loss as we age) and your body fat percentage increases, further slowing your metabolism. Why does RMR matter? Think of it this way. As we get older and our RMR decreases, we burn fewer calories every day if we don't do something to increase the calorie burn, like exercise. This means that even though your habits stay exactly the same, you could start gaining weight. By getting enough exercise now and increasing your RMR, you can be proactive about your metabolism rather than reactive in the years down the road.

You could get injured

I've told clients before that they should think of exercise and fitness as a use it or lose it situation. The more you use your body, the more accustomed it is to movement and the more it can deal with before it becomes fatigued. When you don't exercise, though, your muscles become deconditioned. What this means is that when you are sedentary, the result is a partial or complete reversal of any prior gains in strength, cardiovascular fitness, and flexibility or mobility.

One consequence of these losses in physical fitness can be injury. Have you ever sprinted for the bus after weeks of inactivity only to strain a muscle? That's deconditioning at work. Or maybe you've tried to pick up something heavy (that you used to be able to lift without any problem) and threw your back out or strained your neck. You guessed it, deconditioning. In order to keep your body moving the way it was designed and injury-free, getting enough exercise is key. Maybe you didn't get injured, but are you starting to have more aches and pains? Deconditioning has also been associated with chronic low back pain. So if you're starting to notice a few more aches and a bit more stiffness when you wake up in the morning, it may be time to use it or lose it.

You get grumpy and depressed

If you haven't been exercising enough and you notice you're feeling grumpier or sadder than usual, it isn't all in your head. When it comes to your mood, regular exercise can be a huge factor. For those individuals with clinically diagnosed depression, exercise can lead to a reduction in symptoms. The benefits of exercise are not significantly different (better or worse) from those garnered from cognitive therapy or antidepressants and has been suggested as an adjunct to these types of treatment. You don't need a diagnosed mental illness to reap the benefits of exercise on mood though. Research has shown that people with non-clinical levels of depression and anxiety also benefit from regular exercise.

Those who exercise regularly and then stop or significantly decrease their exercise also see a difference in mood. Have you ever met someone who is training for a marathon and then gets very sad or grumpy when it comes time to taper? Some scientists argue that this is because exercise has an effect on neurotransmitters like serotonin and dopamine levels in the brain, which can help make us feel happy. For people who exercise a lot and then stop, it can almost be like going through withdrawal from a drug. A positive mood is quite a powerful thing. It's also important to note that as long as you're exercising regularly, it doesn't much matter exactly what you're doing. Research has found that improvements in mood and general well-being persist with regular exercise, regardless of whether the exercise was high intensity or low intensity. This means that you don't have to start running marathons or going to CrossFit to see an improvement in mood, you just need to move.

You feel more stressed

If you've ever had a friend talk about going to the gym to blow off steam, she isn't totally off base. Most Americans say they experience stress in their daily lives, with 40 percent saying they experience stress frequently and 36 percent saying they sometimes experience stress. This is important because stress, for which symptoms include increased heart rate and muscle tension, is associated with higher blood pressure, which may lead to heart disease. When your friend says she feels less stressed after spending an hour in spin class or taking a few hits on the heavy bag in a boxing class, she isn't imagining it, but just one class may not make that much of a difference long-term. Both inflammation and oxidative stress have been shown to be important in the development of psychological stress and anxiety. Regular exercise serves as an anti-inflammatory that can help reduce this oxidative stress, thereby reducing psychological stress. In this case, the amount of exercise matters somewhat.

In a study comparing inactive women, moderate exercisers (two-six hours of exercise per week) and vigorous exercisers (more than six hours of per week), researchers found that women who exercised regularly experienced a smaller response to stress. The response to an external stressor produced by the researches was measured both physiologically (through heart rate and cortisol levels) and psychologically (measured by chronic stress and state-trait anxiety levels). Before being exposed to the stressor, the groups of women did not vary in terms of stress level. After stress exposure, non-exercisers showed a higher stress response measured by change in heart rate and self-reported stress than the two exercise groups. Moderate and vigorous exercisers showed lower responses to stress, with vigorous exercisers having a slight edge over moderate exercisers. So while your friend who is at the gym for two hours every day may be cool as a cucumber, spending even 30-45 minutes at the gym every day can help with how your body responds to stress.

Your bones get weak

In my experience as a trainer, many women who do exercise stick primarily to cardio training like running or taking a spin class because they think it's the best type of exercise for their health. While cardio training is important for your heart and is part of the recommendations set by the American College of Sports Medicine (ACSM), it isn't the only type of exercise you should be doing. In fact, resistance training, like lifting weights or doing bodyweight exercises, may be one of the most beneficial types of exercise for women in particular. As we age, our bones get weaker. This is especially true of women who are four times as likely as men to suffer from osteoporosis, which is a bone disease that occurs when the body loses too much bone, makes too little bone, or both. Individuals who have less bone mass to begin with are at a higher risk of developing osteoporosis.

So what does this have to do with exercise? Research has consistently shown that resistance training has a positive effect on bone mineral density in women. By engaging in resistance training before menopause, a woman will increase her bone mass and reduce her risk of developing osteoporosis. For those who are already postmenopausal, strength training is still shown to be more effective for increasing bone mass than non-weight bearing cardiovascular exercise. The ACSM recommends that adults train each major muscle group two or three days each week using a variety of exercises and equipment. If you don't get enough regular exercise, and that includes resistance training too ladies, you may be putting your bones at risk.

You may die younger

Maybe you don't mind if your stress levels are high, your mood plummets, your pants start getting a little snug, and you can't fall asleep at night. Don't you want to live a long life anyway? Numerous studies have shown that in addition to decreasing the risk for certain cancers and improving cardiovascular health, exercise helps you live longer overall. It turns out that regular exercise is associated with a 30 percent decrease in all-cause mortality, that is, all of the things that could possibly kill someone. This means people who exercise are less likely to experience death caused by disease and have a greater chance of dying of natural causes. If you don't get enough exercise, you may be at higher risk for disease and a shortened lifespan. Leading a sedentary lifestyle has been linked with diabetes, cardiovascular disease, and all-cause mortality. It isn't just about weight and sleep, exercise may actually be question of life and death in the long-run.

It doesn't have to happen

A lot of unexpected things happen in your body when you don't get enough exercise, including changes to your physical health and mental health. Many of these changes can be detrimental to your life in the long run so it's important to make sure you're exercising regularly. If you're having a hard time fitting exercise into your schedule, do what I tell my personal training clients and split it into smaller portions. Research has shown that the recommendation of moderate exercise for at least 150 minutes each week can be split into portions for as little as ten minutes and still be beneficial. You don't have to go whole hog all at once. Start small and ease your way in so you can truly make exercise part of your lifestyle long-term. The last thing you want to do is get burned out. For your mind, body, and longevity, it's time to get up and move.