As a personal trainer, I am in and out of health clubs all day. I love to observe the things people do in their efforts to "get in shape". The major thing I notice, is the over-whelming amount of cardio I see women doing while neglecting to do much strength training.

While cardio is an important part of any fitness program, it should not be the primary focus, especially if you are female and over 40 years of age. In your 20s you could knock off those extra pounds by just running on the treadmill a few extra times each week. However, as you approach your 40s and beyond that plan isn't effective anymore and here's why.

As you enter your late 30s you start to lose muscle, and muscle is that part of your body that burns the majority of the calories that you consume each day. A pound of muscle burns about 6 calories a day even while your are resting, and a pound of fat only burns around one calorie per day.

If you don't do anything to combat the above scenario, you can lose as much as 10 lbs of muscle each decade beginning in your 40s. That decreases your metabolism by about 60 calories a day every 10 years of your life. So, that's about 21,900 calories a year that's being converted to fat, which is approximately 6 lbs of fat you gain each year.

I know, this is a very sad scenario, but there is hope. Your saviour is called strength training. By incorporating strength training in your fitness program you can slow, and in some cases, even reverse muscle loss.  And, it's never too late to start, studies have shown the positive results of strength training in people well into their 90s.