At the most basic level, you lose weight when you burn more calories than you consume. But science is learning there’s lots of nuance to weight loss, which is influenced by factors including hormones, sleep quality, nutrient density, stress, the quirks of your own body, and so much more. Still, if you’re trying to shed some excess weight, changing your eating patterns and adding more physical activity can help you achieve your goal, and swimming can and should be part of that picture.