If you’re after general conditioning, maintaining existing muscle mass, and keeping body fat to a minimum, your best bet is to work on BOTH cardio and heavy weight training. Too much steady state cardio per week can actually result in muscle loss! (Which technically you would be losing weight, but it’s not the body fat that you were hoping you would be shedding.)
Lift weights more often than you do cardio. Even though minute per minute, cardio burns more calories than strength training (which could explain why compared to strength trainers, aerobic exercisers may lose more weight in less time), cardio doesn’t do much for your muscles.
And here is why that is important. Strength training is the best way to build more muscle. And long after you’re done with your strength session, your body will continue to burn off calories. Plus, for every three pounds of muscle you gain, you can expect to burn an extra 120 calories a day just being – without moving a single one of those muscles!
Think about going for a long run. After the initial increase of breath and heart rate, you get to that place where everything clicks and you level off and you feel like you could run at that pace forever. Your body get comfortable.
But with lifting those heavy things, your body doesn’t ever hit that “comfortable” place. And because of that it may take your body an hour to recover from a strength session. All the while it’s still continuing to burn calories!
And as an extra bonus, your metabolism stays elevated up to 10% for 3 days after you lift as your body works diligently to rebuild the muscle fibers you broke down while lifting!
Also consider the repeated impact and linear range of motion of running, biking, swimming, or rowing which can create muscle imbalances over time, and repetitive motion injuries and joint problems.
That doesn’t mean that you shouldn’t run though (or row, bike, swim, etc), especially if you’re a stress eater. Cardio is one of the best ways to reduce stress, and stress can often lead to fat gain.
The best plan is a good mix of exercises, intensity, and time domains, but if you only have time for one thing, you should strength train. It’s possible to get your cardio from strength alone. If you keep moving between your sets (either by inserting some power movements between your lifting sets or going straight from one exercise to the next) you’ll strengthen your heart and lungs along with your other muscles!