By New York Times Bestselling Author Michael Levin

When it comes to the aging process, unless you take some proactive steps to slow things down, your body is not necessarily your best friend.

The good news, according to Exercise Physiologist Heather Giordano at Canyon Ranch in Lenox, Massachusetts, is that you can dramatically reduce the rate at which you age through exercise.  And not crazy amounts of exercise, either.  Just 150 minutes a week of moderately vigorous cardio with a well-planned weight training routine and other non-cardio activities gets it done.

“Each of our bodies is different, of course,” Giordano says, “but on average, we can lose a pound or two of muscle every year once we hit 30 if we are not active. Aging actually begins then—not in our 50’s and 60’s, as people commonly believe. So if you start an exercise program now, you can reduce the risk of some of the major killers like heart disease and stroke.”

Giordano points out that 40% of your Fitness Age is a function of your cardio exercise, 30% is due to muscle work and weight training, only 20% to body composition and 10% to agility.  You don’t have to run marathons to reduce your rate of aging or your susceptibility to heart disease, Giordano says – that weekly total of 150 minutes is sufficient.

What’s the best kind of exercise? The answer is: whatever you will do consistently. Don’t focus on what others are doing. When athletes of various activities are brought into the lab, the overall fittest in the world are cross-country skiers. “If you can find somebody’s NordicTrack” Giordano counsels, “buy it and use it! In gyms today, they may have NordicTracks, but they’re often gathering dust in the corner because they’re hard. But they give a really great overall cardio workout.”

In terms of weight training, Giordano says that you don’t need to be lifting Olympic-size dumbbells. You can use smaller weights and more reps. The goal is to work the muscle to fatigue so do what works best for you. Strength training is also beneficial in helping us to preserve bone mass.  It’s frequently said that people “fell and broke their hip.” In reality, their bones got so brittle that they broke their hip…and fell. Why? Because they weren’t involved in weight training.

Obviously, a healthy diet is essential – you can’t out-exercise a poor approach to eating. If you want to change your body composition, which accounts for 20% of your Fitness Age, then you will have to adjust your eating habits as well as your cardio and weight training.  You can’t “earn” a donut with time on the treadmill, because it’s a lot easier to consume calories with snacks than to burn them off.

In terms of agility, the final 10% of the equation, Giordano recommends taking a variety of exercise classes including low impact aerobics, step classes or Zumba so as to increase balance and coordination. These activities also increase one’s aerobic capacity, which make for better cardio and weight training workouts.

“If you want a quick test of how you’re doing,” Giordano says, “stand on one leg and put your knee out at a 45-degree angle. If you’re under 60 years of age, you ought to be able to hold if for 30 seconds. If you’re over 60, then 20 seconds.”

That will show you where you stand, no pun intended, in terms of agility.  If you cannot do that, run, don’t walk to the gym, and remember the 40/30/20/10 rule – 40 percent of your Fitness Age comes from cardio, 30 from weight training, and just 20 from body composition (and 10 from agility).  So since 70 percent come from cardio and weight training, today would be a great day to start (or resume) a program that will let you act your fitness age, and not the measure of how many years you’ve been here on Earth.