Question for Penny:
Why can’t I just do cardio to stay healthy or lose weight (stay in shape)? Why do I have to do weight training or “weight-bearing” exercises?
Strength training burns more fat and calories, and build more lean muscles (which also burns fat). Muscle tissue is more "active" than fat tissue, with each pound burning about 30 calories a day just to stay “alive". So even if you’re sitting on the couch or stuck at your desk for eight hours a day, the extra lean muscles you develop will burn more calories, helping you keep weight off for good.
It has been proven that even though you are burning calories during your cardio session, with strength training you don't only burn calories during the workout, but you can burn more even after the workout, due to the “after-burn" effect. This means that for up to 24 hours or so after the workout has ended, calories are being burned at an elevated level for recovery, blasting more fat even while you’re at rest.
Also, without regular strength training (at least twice a week) to build and maintain lean muscle mass, your body’s metabolism cools down over time and burns fewer and fewer calories. This doesn’t give you much leeway when it comes to enjoying your “fun” foods. Not to mention, without strength training, don’t be surprised if you end up with a not-so-tight, not-so-flattering body composition.
Another important thing to remember: Putting pressure on muscles not only makes them stronger, but it also puts pressure on bones which forces your bones to make new cells, building bone density. This is a good way to avoid osteoporosis (degeneration of bones). So learn to use the machines or dumbbells properly and make it a part of your lifestyle regimen. Heck, you don’t even need equipment; bodyweight exercises such as squats, pushups and planks will do the trick! (As long as you’re doing them regularly.)