Exercise intensity and duration are important for weight loss.
Cardiovascular exercises like running and swimming pack in a host of health benefits, from weight loss to decreasing your risk of cardiovascular disease, and boosting your mood, your immune system and your ability to handle stress. In fact, the Office of Disease Prevention and Health Promotion recommends that adults get at least 150 minutes of moderate-intensity aerobic activity every week, or 75 minutes of intense activity. But keep in mind that not every workout is suited to every body.
Comparing Calories Burned
If you're thinking of swimming or running for weight loss, the amount of calories you burn with each exercise may be a deciding factor. According to statistics from the Mayo Clinic, an hour of light to moderate lap swimming will burn 423 calories, while an hour of running at 5 mph will burn 606 calories.
However, those numbers aren't necessarily the be-all, end-all of your exercise decision making. For example, if you love swimming, it's going to be a better exercise for you than running because you're more likely to keep it up. On the flip side, while not all gyms will have a swimming pool available, almost every gym will have a treadmill of some sort.
The Benefits of Running
Here's some more food for thought when it comes to running: Although not everyone can sprint like an Olympian, running generally comes more readily to people than a truly athletic swimming technique; after all, you've been walking or running for most of your life, and the worst that could happen to you on a treadmill is a trip and fall - you're definitely not going to drown, and you don't ever have to worry about being seen in your swimsuit.
It's also very easy to make your running workout harder (or easier) by altering the speed and incline of the treadmill. Finally, many modern treadmills have interactive programs and entertainment options that can really break up the monotony of a long workout.
The Drawbacks of Running
Although few exercises can beat running when it comes to pure calorie burn, there is one major drawback: Running is a high-impact exercise, which means that it generates a lot of pounding on the joints of your lower body. You don't have to be skinny to run, and you don't have to have perfect knees - but some exercisers who carry extra weight or have compromised joints find that they do better with a low-impact workout such as swimming.
Getting access to a treadmill might be another deal-breaker when it comes to running, but take heart - if no treadmill is available, you can almost always lace up your running shoes and go for a jog outside.
The Benefits of Swimming
While running may be the champion for all-out calorie burn, swimming is hard to beat for other reasons. It's the ultimate low-impact workout, because the water supports your body throughout the entire range of motion. At the same time, the water also provides resistance to your every motion, so swimming is one of the most efficient full-body workouts available.
If you want to really burn calories with swimming, you're going to have to do something more vigorous than a dog paddle, so there may be a learning curve involved. But once you have the proper stroke techniques down, you'll have an easily scalable workout that you can continue doing for the rest of your life.
The Drawbacks of Swimming
Like running, swimming has a few potential drawbacks, the biggest of which are the technique learning curve and finding access to a pool. But swimming is a valuable life - and potentially life-saving - skill that you'll never regret learning. That leaves monotony as the biggest hurdle; if you run on a treadmill, you have many entertainment options at your fingertips, but you can't exactly watch television while you're swimming laps.
Going out in public in your bathing suit might seem like a potential downside to swimming too, but have no fear. Nobody at the pool is going to pay much attention to you, because they're all concerned about how they look in their swimsuits too. If modesty is a true concern for you, you can add swim shorts or a rash guard (a water-ready T-shirt used by surfers) to your swim ensemble.
Can't decide between swimming and running on a treadmill? Try them both, and give yourself a few weeks to figure out which one you enjoy the most for its own sake. That's the exercise that will do you the most good in the long run.