A few things:
1.) You couldn't outrun a poor diet- I'm not assuming your diet is poor. My point is to say that you can run 20+ miles a day, but if your diet isn't setup properly you're not going to lose weight (and you may even gain some).
2.) Running, swimming, and high repetition/low weight lifting is cardio to me. Personally, I think that cardio is an integral part of one's general health, but I don't consider cardio to be one of the more effective ways to losing weight. Basically, when I go for an hour long run it's meant for my general health rather than to lose weight.
3.) Heavy weight lifting- While I still consider it a very small part of the equation, I think it's the most effective type of exercise when it comes to weight loss. First, heavy weight lifting promotes muscle growth/retention. When losing weight, you want it to be fat loss rather than muscle loss. Second, weight lifting causes your body to burn calories hours after you finish a (hard) workout when compared to cardio where your body adjust quickly after you stop. Third, heavy lifting helps ensure that if you're going to GAIN weight, it has a high likelihood of being primarily muscle. That may seem odd in this context, but if you're struggling to lose weight the last thing you want is to pack on additional body fat. Few would complain about adding additional muscle.
4.) When someone tells me they're having trouble losing weight, the first thing I ask is for them to be more specific. 99% of the time, those people don't have a diet plan outlined, aren't keeping a food log, aren't measuring their food portions with a scale,etc. Those things may seem unnecessary, and for the most part they are, but if you're struggling to lose weight you need to pinpoint EXACTLY where and why. The fact of the matter is that for MOST people (but not all) it's an issue of lifestyle intervention (making the necessary diet/health changes) rather than a metabolic or body-related issue.
