Body fat composition typically recorded as body fat percentage is not only a good measure of risks (diabetes, cardiovascular disease), it is a good way to measure progress with exercise. The more muscle you have, the lower your body fat %, and vice versa (Figures 1 & 2).
Figure 1. Graphical depiction of body fat % in women
Figure 2. Graphical depiction of body fat % in men
The gold standard for measuring body fat percentage these days is MRI, with a range of tools that decrease in costs and accuracy. Two common ways to measure body fat percentage at home include skin fold measurements (using calipers), or biometric impedance analysis (BIA). I recently purchased a wireless scale for $99 that measures both weight and body fat percentage using biometric impedance and directly connects to my home wireless network to log both values into a dashboard online (Figure 3).
Figure 3. Fitbit Aria 2 Scale
Biometric impedance uses small and safe electrical impulses to measure total body water, which is used to estimate lean or fat-free body mass, which is subtracted from your weight to determine body fat percentage. Keep in mind that biometric impedance is far from 100% accurate and can vary based on your hydration status (drinking enough water). It is most likely best suited to measure progress in one direction vs the other, in relation to increases or decreases in exercise activity.
Measuring body fat percentage with calipers is thought to be more accurate than biometric impedance, although, it requires an additional person to take accurate measurements, and measurement accuracy can vary with the skill of the person taking the measurement (intra-observer variability).
Figure 4. Skinfold Caliper
Using calipers with a set “pinch” pressure, you typically take measurements in 1-7 locations, which can vary depending on the person’s gender and familiarity by the person taking the measurement. Frequently used locations include the chest (midway between axillary/armpit crease and the nipple), back of the arm (over the triceps), front of the arm (over the biceps), below the shoulder blade (sub-scapular), the abdomen (1 inch lateral or to the side of the belly button), at the waist (Supra-iliac), and the thigh (midway between the hip and knee at the front of the thigh). For men, measure skin fold thickness at the thigh, chest and abdomen, for women measure at the thigh, triceps and supra-iliac. Body fat percentage > 32% in women, and > 26% in men is classified as obese.
Here is a table from the American Council of Fitness (Figure 5) that aligns average body fat % in men and women with overall fitness. Measuring body fat % in individuals is a great way to understand how your nutrition and exercise add up to changes in lean body mass.
Figure 5. American Council of Fitness body fat % table.