- Watch what you eat/count calories
- Lift heavy weights
- Do cardio
#3 on its own is rarely ever going to show results. So many people will jog for an hour or more every day and then eat a candy bar as a reward, instantly undoing all the work, then eventually get discouraged when they see no progress.
While weight loss is mostly diet, if you did want to use exercise to burn additional calories, cardio would do more than weight training. I burn up to 1000 calories in an hour of very strenuous cycling (from normal weight), which I doubt I could ever do lifting dumbbells and barbells.
I've always used weight training during weight loss to try and tell my body to retain muscle and target fat primarily.
the way i always think about it is that humans are among the most efficient runners in the entire animal kingdom; some tribes in Africa still practice persistence hunting. so by extension, cardio is going to be the worst choice for weight loss - but the other benefits still make it worth it.