Q: mike can you still lose weight, if you only weight train, without any cardio.

A: Yes, you can definitely lose weight and fat very effectively without doing any cardio, if you have a good whole-body weight training program and a good nutrition plan.

Cardio is great for your overall health, but it is limited as far as its fat-burning potential. It certainly burns calories while you exercise -- typically 600 calories or so per hour or running. That means you need to run for 6 hours to burn 1 pound of fat. More importantly, running does not boost your metabolism once you're in decent shape (it definitely does boost your metabolism if you start in really poor shape). This means you don't get any 'bonus' calorie burning after you finish running while your body recovers. In fact, if you run too much, and especially if you eat little, there's a good chance a lot of running will actually depress your metabolism which means your body gains new fat easier than before.

This is very different from heavy whole-body weight training. Weight training also burns some calories during the exercise itself. But that's not its main fat-burning benefit. What happens during heavy weight training is your muscles sustain significant physical damage that your body then needs to repair. This kicks off a flurry of processes in your body all of which burn calories after the exercise and raise your metabolism. This means the fat-burning continues for days after you are done exercising and your body becomes resistant to building new fat. The net effect is that with less time spent your body burns more fat and becomes resistant to new fat. The keys here are to lift heavy (heavy for you, not for somebody else) and to focus on big compound exercises like squats, deadlifts, lunges, rows, pullups/pulldowns, and presses -- you won't burn much fat doing endless bicep curls. Read my Weight Training article to learn how to weight train effectively.

Your diet is very important too, of course. You need to eat enough to support muscle repair and not cause your body to start burning muscle instead of fat for energy which you body can do if you are eating too little. You also can't eat too much or else extra calories start going into new fat. And not all calories are created equal, of course. You need a balance of lean protein, slow-digesting carbs, and healthy fats. Fortunately it sounds more complicated than it really is -- just read my Nutrition article.

So while most people will derive benefits from at least some cardio, it is definitely not necessary if you have a good weight training program and eat right.