Is running or swimming better for weight loss?

For pure calorie burn per session, running edges out swimming at a similar perceived effort level, mainly because running is weight-bearing and your body works harder against gravity the whole time. A moderate 30-minute run typically burns somewhat more than 30 minutes of moderate swimming for most people. But better for weight loss really comes down to which one you'll actually keep doing consistently, and that's where swimming has a real edge for someone returning after a couple of years off. Running is high-impact on joints that haven't been conditioned in a while, and a lot of people get an early injury that stalls momentum in the first few weeks. Swimming is low-impact, works your whole body, and lets you build a cardio base without the same injury risk while you're getting back into shape. My honest suggestion: start with swimming for the first month or two to build a fitness base without injury risk, then introduce running gradually once your joints and cardiovascular system have caught up. Weight loss ultimately comes down to consistency and a sustained calorie deficit far more than which specific cardio activity you pick - the best exercise for weight loss is genuinely the one you'll still be doing in six months.