There are benefits to both swimming and using the elliptical machine if your goal is weight loss. Swimming and the elliptical are both low-impact workouts, so they're safe for weak joints and easier for obese people. Both exercises are high calorie burners and build muscle all over your body, boosting your metabolism. Your intensity and the types of swim strokes you perform will determine which workout is more effective for weight loss.
To lose weight, you need to burn off pounds of fat by expending more calories than you consume. Because both swimming and the elliptical work your upper body, core and lower body at the same time, they both burn calories at a high rate. Just 30 minutes on the elliptical burns about 335 calories for a 155-pound person. Swimming at a moderate to high intensity by doing the breaststroke, butterfly or a vigorous front crawl burns 370 to 410 calories. However, when exercising at a low intensity you'll burn more calories on the elliptical than you will when performing the backstroke or front crawl.
Water serves as resistance against your muscles, and you use all your muscles to swim, no matter which stroke you do. Besides torching calories, swimming laps also helps to build muscle mass. The elliptical does, too, working your core, hips, glutes, thighs, calves and arms -- if you use the arm handles. The elliptical is considered a good cross trainer for runners and cyclists because it builds the hips and glutes. These muscles will balance out strong quads and hamstrings and increase overall power.
If you use proper technique for various swim strokes, like the breaststroke and butterfly, and do them at a steady or vigorous pace, you will get a more effective workout than exercising at a moderate pace on the elliptical. However, using the elliptical at a vigorous intensity may burn as many or more calories as swimming laps. No matter which exercise you do, you'll burn more calories if you include high-intensity intervals. In the pool, swim one lap as vigorously as you can, then swim one or two easy, recovery laps. On the elliptical, go at a moderate pace for about five minutes, then increase the resistance and your speed to a high intensity for one minute. Complete four or five high-intensity intervals over the course of a 20- to 35-minute workout.
The best choice for weight loss may simply be whichever you enjoy doing more, because you're more likely to stick to your workout and do it at a high intensity if you're happy with it. If you can save time by buying an elliptical trainer for your home, this may help, as you won't need to leave for the pool. Varying your workouts challenges your muscles by forcing you to use different movement patterns. For optimum weight loss results, include both the elliptical and swimming as part of your cardio program. Do different swim strokes to emphasize different muscles. Also, do two strength-training sessions each weak that target all your major muscle groups.