It's easy to find reasons not to exercise: It's cold outside, you have a million things to get done, or you'll do it tomorrow. But before you know it, you haven't exercised in who knows how long.

Skipping the gym every once in a while is nothing to worry about. In fact, it's good to give your body time to recover from intense workouts and build muscle mass.

However, you don't have to wait for dust to collect on your sneakers before your body starts reacting negatively to the break from physical fitness.

According to the Mayo Clinic, here are seven ways your body is ruined when you stop exercising:

You gain water weight

Many people don't worry about how a week off from exercise will affect their weight; but after going only one week without exercising, your body begins to retain more liquids, which can make you feel and look bloated.

You lose cardio endurance

You shouldn't be surprised to learn that the longer you put off facing the treadmill, the more challenging it will be to outrun ravenous zombies in a potential apocalypse. What may surprise you is that your cardiovascular endurance will noticeably decline in as little as two weeks.

This happens because the number of mitochondria, which fuel your muscle cells, decreases when you stop exercising, making it harder for you if you decide you'd rather not face the gym for a couple of weeks.

You feel more tired

When you stop exercising for a few weeks, your heart has to work harder to beat. This means that your lungs aren't able to absorb as much oxygen. This strain and lack of oxygen fatigue your body, making you more tired overall.

You can't sleep

Even though skipping workouts can make your body extra tired, sleeping becomes challenging. Exercise supports your circadian rhythms, or your process of living in a 24-hour period. When you disrupt them by neglecting exercise, you become more stressed and have challenges sleeping.

So if you're struggling with insomnia more and more, it's probably time to add exercise back into your routine.

You get depressed

Exercise triggers the release of endorphins in your body. These chemicals reduce pain and create positive feelings in the body (much like morphine).

Furthermore, exercising increases your self-esteem in more ways than one, which contributes to your overall happiness.

It's for these reasons that scientists cite depression as a negative side effect of not exercising.

You burn less calories

When you participate in a regular exercise routine, your body burns more calories — even if you're just sitting. However, if you persist in skipping exercise for over a month, your metabolism is weakened. This means that you don't burn as many calories.

You get sick

When you exercise, your body makes more bacteria-fighting cells (macrophages) and they are able to move more quickly through your body, giving you a more efficient immune system. Limiting your exercise also limits these benefits, making you more susceptible to illness.

If your "break" lasts close to a year, the risks increase. You could be facing diabetes, insomnia, high blood pressure, high cholesterol, obesity and clinical depression. While there are always reasons not to exercise, there also are these pretty important reasons toexercise. Make sure you make exercise a priority.