Your workouts are important to you, but life, work, and even just plain burnout can get in the way and lead you to skip a few – or a bunch of – days.

While taking rest days is essential to helping your body recover and build muscle, taking too much time off can be detrimental to your overall health and fitness level.

Don’t let a lack of motivation, a confusing schedule, or burnout affect you for too long! Here are 8 bad things that happen to your body when you don’t regularly exercise:

Loss of Aerobic Capacity

Working out is great for your heart, even if you aren’t focusing solely on cardio. It’s a muscle just like your biceps and quads, and the more you work it, the stronger and more efficient it gets at pumping blood to the rest of your body.

After a few weeks of not exercising, your heart begins to lose its ability to handle the extra blood flow that comes with working out, but your body’s ability to utilize oxygen – your VO2 max – decreases.

Studies have shown that your body sees significant decreases in your VO2 max and overall aerobic capacity within two to four weeks of stopping physical activity. Everything you’ve built up in aerobic capacity in the last two to three months can be gone in a matter of weeks.

While this loss will be most noticeable when you decide to workout again, you may see that you’re struggling to catch your breath going up flights of stairs at home or work, for example.

Decrease in Muscle Strength

Just as your heart gets stronger when you workout, the rest of your muscles get stronger, too. And if you’re not using those muscles in the same way after a while, they’ll begin to lose their strength.

Over the first few weeks after you stop working out, you’ll notice that some of your muscles appear smaller. By the time you reach 12 weeks without training, you will see decreased muscle mass and muscular strength. This could mean that what you once used as your warm-up weight will become your max when you come back to the gym.

Good news, though: Muscle memory can help you bounce back to those PRs fairly quickly once you get back to training.

Increased Blood Pressure

Regular exercise is a well-known way to decrease your blood pressure. It’s so well-known, in fact, that many doctors prescribe an exercise regimen to help naturally treat hypertension.

While not exercising for a while doesn’t mean you automatically will develop high blood pressure, it can still cause problems. If, for example, you already have elevated blood pressure or you are at risk for hypertension, not working out can cause your blood pressure to rise again.

As with your aerobic fitness and muscle strength, re-starting your exercise regime can help improve your blood pressure.

Note: If you are using exercise to control your blood pressure, please be sure to consult with your doctor if you anticipate not working out for long periods of time.

Higher Blood Sugar

When you eat, your blood sugar rises. It then drops as your muscles and tissues absorb the sugar from your digested food, turning those sugars into energy.

By working out, you decrease those blood sugar levels, as you’re burning the energy from your food to fuel your exercise.

Over time, your body gets used to those lower base blood sugar levels. When you stop exercising, your blood sugar increases and, as you eat food, it increases even more.

A study in Medicine & Science in Sports & Exercise showed that, in young, healthy individuals, blood sugar levels remained elevated after just three days of inactivity. So, unlike losses in aerobic capacity and muscle strength, the negative impacts of not exercising on your blood sugar levels are much more immediate.

Decreased Metabolic Rate

Do you notice that, when you start working out or increase your activity levels, your appetite skyrockets? This is because exercise revs up your metabolism, causing you to more quickly digest the food you put into it.

But when you stop working out, your metabolism slows to support your decreased activity level. In a lot of cases, this decreased metabolism doesn’t come with a decrease in appetite, meaning you may unconsciously continue eating as if you’re working out.

Over time, this can lead to increased caloric intake and weight gain, reversing any progress you’ve made in your fitness journey.

Increased Stress Levels

Working out is often referred to as people’s “stress relief,” as a good sweat session can do wonders for your mood and stress levels.

When you workout, you release endorphins, or “happy hormones.” These endorphins help regulate your mood and manage your stress levels. So, if you workout in the morning and your boss dumps a project on you at noon, you’re more likely to have a more calm, measured response than if you were overly stressed.

By not working out, your endorphin production is much lower, meaning your ability to regulate your emotions and stress levels is also decreased.

If you find yourself suffering from a hair-trigger temper when you miss the gym for a couple of days, you know this one’s true!

Worse Sleep

It makes sense that the more energy you expend, the more tired you’ll be at the end of the day, right? And the better you’ll sleep at night?

If you work at a largely sedentary job – as many of us do now – working out is often the largest sustained block of physical activity we get in a day. Think back to when you first started exercising: You came home at the end of every day exhausted, and fell asleep pretty soon after your head hit the pillow, right?

When you don’t workout, you’re not getting that large energy expenditure which can lead to more difficulty falling asleep. After missing a few days of workouts, you may find yourself tossing and turning when you first get into bed, or waking more frequently at night, overall decreasing the amount and quality of sleep you get at night.

Brain Fog

Everyone’s attention is really scattered, with our brains constantly holding our big project due dates, kids’ doctor appointments, grocery lists, and world happenings like a bunch of spinning plates. Being able to sit down and really focus on the task at hand, whether it’s a meeting, a conversation, or a column of numbers, can be difficult.

Working out can help clear out this “brain fog” and improve overall focus and productivity. Rather than sitting and staring at your screen for an hour, your daily workout clears your mind and allows you to get your work done more efficiently and effectively.

But when you stop working out, this brain fog can return – often paired with poor sleep and an overall feeling of sluggishness – meaning you’re unable to work to the same level you were when you were getting your daily workout in.

Skipping the Gym Happens – But Prepare for It!

Periods of detraining are totally normal. Whether you’re nursing an injury, things are busy at work, you’re moving, or you’re just in a funk, taking some time away is perfectly OK – and even healthy.

But if you’re planning on an extended period away from the gym, just be sure you understand the changes your body, mind, and attitude will go through and prepare for them accordingly!