If you’re getting a little tired of spare tires and muffin tops, never fear. There’s no time like the present to take solid action towards a healthier, trimmer body—for good. This time, however, be sure you start with the right information. The best way to begin a successful weight loss/fitness program is to determine your body composition—the ratio of body fat to lean muscle—through body fat analysis. This simple test is available at gyms, health clubs and medical facilities.

Why is this an essential baseline? It turns out that your body composition has a direct impact on your weight, fitness, health and life expectancy. Though you may have relied on your bathroom scale in the past, it’s a highly inaccurate gauge of fitness because it fails to differentiate between fat and lean muscle. Fat weighs considerably less than muscle, but takes up much more space.

According to the World Health Organization and the National Institutes of Health, an ideal body fat range for women ages 41 to 60 is 23-35% and 11-22% for men 41 to 60. However, many health experts recommend that for optimal fitness, men should aim for 8 to 12% and women for 12 to 18%. Determining your body composition will clearly provide you with the most accurate starting place for healthy weight loss.

If you have a higher than ideal percentage of body fat to lean muscle, reducing the fat while protecting your lean muscle is your best bet to attain—and very importantly, maintain—a healthy weight. Checking your body fat percentage every few months will allow you to effectively track your progress as you move towards a healthier, trimmer, stronger body. Lose it smart—for the last time.