We've all heard a hundred times that the key to weight loss and a healthy body is a sound diet and exercise. Many of us work hard to keep our diets in check, but have a hard time when it comes to exercise. Either we're short on time, feel too tired, or just don't have the motivation to get up any earlier.

Well, if you're one of those that has a hard time with exercise, I've got good news for you. Exercise doesn't have to be that hard! You don't have to spend an hour at it, and you don't have to join a gym or buy expensive equipment.

In fact, just 20 minutes of exercise per day can give you great health benefits over the long haul. Even if you only do 5 or 10 minutes at a time, you're still doing your heart--and your physique--a lot of good.

When you're short on time, you can sneak your exercise in just about anywhere you are. It's amazing what a little heart-pumping here and there will do for your health AND your mood.

Pulling a stressful 9-to-5 shift? Take a 15-minute break twice a day and go for a walk...even around the office or up and down the stairs. The exercise will not only burn a few extra calories, but it will also help you avoid that afternoon slump and put you in a better frame of mind.

Got too much laundry to worry about exercise? Use your chores as a workout. Take a few extra trips up and down the stairs, dance while you dust, or vacuum whether you need to or not. Load the dishwasher in a squat position to tighten those glutes, and keep those abs pulled in no matter what you're doing.

While you're out doing your regular errands, get a little exercise as well. Park at the far end of the parking lot to do a little walking. Contract your arm and back muscles while you push that shopping cart. Carry your toddler instead of having her walk. If you only have a few items to get at the store or have a neighborhood delivery to make, walk!

If you can, set your alarm just 20 minutes earlier and grab your dumbbells. Find a few exercises on the Web and alternate working different parts of the body on different days. Weight-bearing exercise is the best way to increase your lean muscle mass, which will boost your metabolism and help you stay fit. You'll also get stronger bones! No dumbbells? Use soup cans or gallons of milk.

If you're trying to lose weight, exercise will get you to your goal much faster, and you'll form a healthy habit along the way. It takes just 21 days to form a habit, so if you can commit to exercise several times a week for just the next three weeks, it will become easier to keep it up. You will probably even decide you enjoy it!

Remember, exercise is any activity that gets your heart rate into its target zone. You don't have to sweat it out in front of a video or in an organized class. Your exercise can be walking, dancing, tennis, football, biking, or any other sport or physical activity you enjoy. As long as you keep it up and use variation to keep from getting bored, exercise can be an enjoyable, permanent part of your new healthy lifestyle.