If you’ve been reading my series on body fat testing, you have now learned that even the best techniques have larger error rates than most people realize.

Does this mean body fat testing is useless for individuals? No, but it does mean you should exercise caution when using these techniques, and be aware of the large error rates. Here are some important tips to keep in mind:

  1. Always remember that any number you get from a body fat test is a VERY rough estimate, and could be significantly off.  Thus, don’t put too much faith in the specific number.
  2. Point #1 holds true even when measuring change over time.  I’ve heard many people say things like, “I lost 4 pounds of fat and gained 1 pound of lean muscle.”  The numbers are never even close to being this precise.  Given the error rate for measuring change over time, there’s a good chance those numbers are way off.
  3. Even the best techniques have a 4-5% error rate when measuring change over time.  This means, to accurately detect a decrease in body fat in most people, the body fat percentage needs to drop by a minimum of 4-5%.  This means you should take long periods of time between measurements.  I would say a bare minimum of 3 months, but 6 months is probably better.  I see too many people taking measurements as often as every 4 weeks or so.  That’s too frequent and unreliable.
  4. Remember that fat-free mass and muscle are not the same thing.  So just because your fat-free mass increases, doesn’t mean you had an increase in muscle.
  5. You don’t need to have your body fat tested.  A combination of body weight and circumference measurements (like waist circumference) will give you a very good gauge of whether you’re losing body fat.  If your circumference measurements are decreasing, you are likely losing fat.
  6. If you are going to try to track change in body fat over time, then I recommend hydrostatic weighing or skinfolds.  These methods have shown the best accuracy rates for measuring change over time.  However, these techniques are difficult to do with extremely obese people.  For extremely obese people, I recommend simple body weight and circumference measurements.
  7. When using skinfolds to track change over time, you don’t even need to bother calculating a body fat percentage.  If the sum of your total skinfolds is decreasing, then you are likely losing body fat.
  8. Whatever technique you choose, keep the conditions as identical as possible between measurements.  That means having the same technician perform the measurement on you, using the same equipment, and at the same time of day.

I hope you enjoyed this series on body fat testing, and I hope it opened some eyes regarding the techniques that are out there.  Again, body fat testing isn’t useless, but you do need to be careful in how you interpret the results.