Body Fat Percentage: Bio Markers of Aging Series

What weighs more? Fat or muscle? That’s a question I’ve asked my audience at times when doing a guest speaking gig. You’d be amazed at the answers I get! Most times the answer is that muscle weighs more because it’s more dense than fat. A true statement but not the right one.

What I’m looking for in order to illustrate my point is that they weigh the same, if they are indeed the same weight! A pound of muscle weighs exactly the same as a pound of fat. One just takes up a little more space than the other. But, even if fat did take up a little more space, it just doesn’t look as pretty as muscle!

This article/blog is dedicated to the 10 bio markers of aging (see list below). In the last installment, we took a look at Basal Metabolic Rate (BMR) in regards to the relationship it plays in our bio markers of aging series. We’ll now look at our forth bio marker to aging: Body Fat Percentage or BFP.

What is a healthy body fat percentage for men and women?

Figure 1. Body Fat Percentage Chart


What are the benefits to having a healthy body fat percentage?

The ratio of your lean muscle tissue versus fat mass is perhaps the most misunderstood concept in a successful weight management program. Muscle tissue compared to fat is metabolically active. Those who are able to maintain healthy BFP’s will burn more calories at rest versus those who have higher BFP’s. The breakdown and synthesis of muscle protein is the principle reason for the energy expenditure when muscle is at rest.¹

Total energy expenditure is the sum of the calories you burn at rest (resting energy expenditure or REE, the energy you burn eating food, as well as the energy you burn when active). Most of us get too caught up in how many calories a certain activity or exercise will burn, or that the number of calories burned using a particular type of exercise machine is the REAL secret. The real secret in fact is how many calories you’re burning the other 23 hours of the day! Here is a short list of some of the benefits to having a healthy body fat percentage…

  • Decreased risk of cardiovascular disease
  • Decreased risk of metabolic disease
  • Decreased risk of various cancers
  • Decreased risk of sleep Apnea
  • Decreased risk of developing osteoarthritis
  • Decreased risk of gallbladder disease
  • Decreased risk of stroke
  • Not to mention you’ll feel and look better!

What are the negative aspects of having an unhealthy body fat percentage?

Refer to all the benefits (above) of having an acceptable body fat percentage and replace the word “decreased” with “increased”.  I won’t elaborate much more about that. Thus, if you’re  motivated to make healthier lifestyle changes by avoiding the negative aspects, so be it. It’s a real downer.

What methods are used to calculate body fat percentage?

For many years, hydro-static weighing (under water) was considered the “gold standard” to calculate BFP because of it’s very accurate results. However, most of us don’t have the equipment to use it, it’s a little more costly, and who wants to be dunked under water several times while breathing all the air out of your lungs to get that result? Other newer methods like X-raysbody plethysmography, and MRI’s are great but again, it’s costly and you have to jump through other hoops to have it done.

Bio-impedance or Bio-electrical impedance, using electrical current, is also another method of obtaining BFP. A higher than normal BFP will be detected if the subject is dehydrated. This is because the level of water and electrolytes both positively affect the small current of electricity used with this method.

At Mitchell Fitness Systems, we’ve always had great success using skin-fold calipers using a simple three site formula to come up with a result (a seven site test is more accurate but not by a whole lot!) If the customer is too obese or doesn’t prefer caliper testing, we’ll simply do circumference measures on a few body parts (waist, hips, thigh, etc) or as a last resort, use BMI or Body Mass Index.

There are numerous methods for calculating BFP. Keep in mind that whatever method you choose; stick with that method when comparing results from one test to the other. You cannot compare tests from different methods because each method has it’s own test reliability result. More importantly, the result from one test to the next, using the same method, is far more important than the accuracy of the method you choose.

What is the difference between using BMI and other methods to calculate BFP?

Because it’s hard to measure numerous populations using more accurate methods of testing body fat percentage, obesity is generally measured using BMI (rating number given by calculating height and weight). Our government, epidemiological researchers, and insurance company’s use this method, for this very reason and also because it’s simple and has no cost.

The problem with BMI is that it may only tell part of the story. To illustrate my point, I’m 6′ 1″ tall and I weight 234 pounds. That puts me in the “Obese” range (see figure 2 below). However, I currently have a 12% body fat percentage (see figure 1 above). That would be considered a classification of “Athletes”. So, BMI is not a good way to measure those who are more fit and athletic. BFP testing trumps BMI in many regards to a determination of health.

Figure 2. Adult BMI Rating and Status Chart

What can you do to move toward a healthier body fat percentage?

Get off the couch and move your butt! That’s a start! Begin to form healthy habits of a regular exercise program including a good basic strength training program at least 2 to 3 days weekly. Increasing, or at least maintaining, muscle mass as you age is crucial. Also, find activities that you enjoy, like biking, jogging, or hiking, and do it regularly! Find ways to increase, not decrease, daily activity levels, and you’ll be well on your way to a happier healthier life!

The fuel you put into your body (quality) as well as the amount (quantity) is important to lowering your BFP. When you eat (timing), would be another good habit to cultivate, but only when the habit of quality and quantity is solidly in your daily routine. Currently, at Mitchell Fitness Systems, we use the Precision Nutrition system with great results and like it because of it’s healthy aspects and simplicity.

Since stress is another cause of higher body fat levels, getting involved in things that promote lower stress in your life is a great idea. This can include exercise like yoga or other stretching type activities. If you suffer as many do with emotional pain, getting involved in a good 12 Step Program like AA or Celebrate Recovery is a wise idea.

How much time will it take to reach my goal of being in the healthy body fat percentage range?

Picture yourself one year from now. You can either continue to sit around and eat unhealthy or you can begin to incorporate healthy exercise and nutritious habits to make some great changes in your life. One year will pass regardless of the choice you make. What sounds better to you; what you have now or a healthier and fitter you? It’s amazing how much progress a person can accomplish with very little time put into a well rounded exercise program. Everyone has 168 hours in a week. If you spent just three hours weekly exercising, that would be under two percent of your week! A great return on your time investment (ROI) to say the least!

Let’s talk about what happens as we age in regards to the amount of muscle mass we lose and the amount of fat we gain and how this effects the aging process.

Sarcopenia, a degenerative condition pertaining to a loss of muscle mass from aging or inactivity, is preventable and reversible to some extent. When we were younger, we were more active and used our bodies more. For men, the average BFP at age 25 is around 18%. In contrast, when a man reaches the age of 65, the average BFP is 38%. For women, the average BFP at age 25 is around 25%. In contrast, when a woman reaches the age of 65, the average BFP is 43%.²

So, why does this happen? As stated, when young we used our bodies more because we were more active. Playing sports or participating in other physical activities regularly kept our BFP at a healthy classification. I’m almost certain you may even remember eating way more when you were younger too and if you were active, staying pretty fit!

As we aged, we became less active and maybe ceased sports activities as well. The response to this decrease in activity was also a decrease in lean muscle mass. You may even be eating less than you used to! Remember, strong muscles (over 600) lead to strong bones (over 200): And that leads to healthier guts (heart, lungs, digestion, etc.).

Next month, we’ll look at the 5th bio-marker to aging: Aerobic Capacity and it’s effects on your cardiovascular (heart and venous) and pulmonary (lungs) systems.

10 Bio-markers of Aging

1. Muscle Mass

2. Strength

3. Metabolic Rate

4. Body Fat Percentage

5. Aerobic Capacity

6. Blood Sugar Tolerance

7. Cholesterol/HDL Ratio

8. Blood Pressure

9. Bone Density

10. Temperature Regulation

¹ Wolfe, R.R., The Underappreciated Role of Muscle in Health and Disease, The Am. Jrnl. of Cln. Nutr., 2006;84:475-82

² Evans, W., PH.D. and Rosenberg, I.H., M.D., Biomarkers: The 10 Determinants of Aging You Can Control, pgs. 53, Biomarker 4: Your Body Fat Percentage, Simon & Schuster, 1991.

Trent Mitchell, M.S., C.S.C.S., is the owner of Mitchell Fitness Systems, Inc. in Torrance, CA. To reach him for guest speaking engagements of for personal training services, call 310-961-2610, email, or go to and click on the link “Guest Speaking” under the “Services” link.

Leave a Comment