Cardiovascular workouts, such as swimming, are effective for lowering your body fat because of their ability to burn a large number of calories. Whether or not you lose fat with exercise depends on how frequent you are with your workouts and your eating habits. However, while swimming will help you lower your body fat, in some circumstances it can cause the number on the scale to increase.
Fat Loss from Swimming
According to the American Council on Exercise, swimming is among the most efficient types of workouts for burning calories. A person weighing 140 pounds will burn about 9 calories every minute he swims at a moderate pace. A 160-pound person will burn about 10.3 calories per minute and a 180-pound person will burn about 11.6 calories every minute. This means that a person between 140 and 180 pounds can burn approximately 270 to 348 calories in a 30-minute workout. To lower your fat, you've got to burn 3,500 more calories than you consume. Therefore, a person weighing 140 to 180 pounds can reach this deficit in 10 to 13 30-minute swimming workouts.
Fat vs. Weight
When you step on the scale, the value it reads is how many total pounds your body weighs. This number makes no distinction of your body composition. For example, a person with a lower body fat percentage but a large amount of muscle mass can weigh the same as a person with a high percentage of body fat with little muscle mass. Swimming, because of the calories it burns, will help you lower your body fat, but it also has the potential of making you weigh more because of another effect that comes from consistent training.
Weight Gain from Muscle Mass
According to Columbia University Health, studies looking at weight loss effects from swimming have been inconsistent. Some studies have found that the exercise is effective for weight loss, while others have shown no difference and even weight gain. They note that the cause of swimmers in the study gaining weight came from an increase in muscle mass and not due to putting on more fat. As you put on lean muscle, you will notice an increase in body weight. However, at the same time, you will notice that your clothing size decreases.
Results of Eating More
Another reason swimming may cause you to gain weight is because you could be eating more. Columbia University Health notes that people have a tendency to consume a greater number of calories after a swimming workout in cold water. If you increase the number of calories you consume, you could cause a caloric surplus instead of the deficit you need to lower your fat. This cause of weight gain is due to an increase in body fat and should be of concern. Therefore, monitor the food and drinks you take in to ensure you're not consuming a greater number of calories after your swimming sessions.