Anthropometric measurements are a series of quantitative measurements of the muscle, bone, and adipose tissue used to assess the composition of the body. The core elements of anthropometry are height, weight, body mass index (BMI), body circumferences (waist, hip, and limbs), and skinfold thickness. These measurements are important because they represent diagnostic criteria for obesity, which significantly increases the risk for conditions such as cardiovascular disease, hypertension, diabetes mellitus, and many more. There is further utility as a measure of nutritional status in children and pregnant women. Additionally, anthropometric measurements can be used as a baseline for physical fitness and to measure the progress of fitness.
There are several possible indications for anthropometric measurements. In children, indications include stunting, wasting, and being underweight. Stunting is when children have a low height-for-age, wasting is a low weight-for-height, and underweight is a low weight-for-age. Mid-upper arm circumference (MUAC) is a viable measurement in children or pregnant women as a marker of nutritional status. BMI is another commonly employed index of nutritional status and used to gauge malnutrition in children and adults. BMI is useful to identify obesity and the severity of obesity. Anthropometric measurements are often also used as part of the evaluation of fitness in athletes.
There are few contraindications to anthropometric measurement. The contraindications would result from conditions that would make taking the measurement impossible or inaccurate, such as amputations or casting.
The exact technique, such as what side of the body to measure and what decimal point to round to, can vary from one study to another but should remain uniform within studies.
Weight measurement should be in kilograms. To measure infants or children who are unable to stand alone on the scale, first have an adult stand on the scale and zero the scale with the adult standing on the scale. Then hand the child to the adult to obtain an accurate measurement of the child.
When measuring height, the patient should stand with his or her heels together and weight evenly distributed. Patient positioning should be with the shoulder blades, buttocks, and heels on the stadiometer's vertical backboard. If not able to have all three points of contact on the vertical backboard, the heels and buttocks must touch the vertical backboard. The feet should face outward at a 60-degree angle. If the patient has genu valgum, separate the feet enough to avoid overlapping the knees while maintaining contact between the knees. Arms should be loosely hanging at the sides with palms facing the thighs. The horizontal bar of the stadiometer should be lowered until the hair is compressed to the crown of the head. Remove any objects on the head or hair that obstruct the bar from compressing the hair to the level of the crown of the head.
To measure upper leg length, have the patient seated with legs at a 90-degree angle. Then, run the measuring tape from the inguinal crease immediately distal to the ASIS to the proximal aspect of the patella.
To measure the upper arm length, find the superior edge of the spine of the scapula. Then, run the measuring tape down the center of the triceps to the olecranon.
Immediately after measuring the upper arm length, the mid-point of the arm should be marked in preparation to measure the mid-upper arm circumference. The patient stands upright with the arm hanging freely at the side. The patient should not flex the arm muscles. Measuring tape placement should be snugly around the mid-point of the arm without compressing the skin.
For infants, measure head circumference by placing the tape measure above the eyebrows, above the ears, and over the occipital prominence. Tighten the measuring tape until there is a snug fit.
To measure waist circumference, patients should stand with the arms crossed on the contralateral shoulders. The placement of the measuring tape should be snugly around the lateral aspect of each ilium at the mid-axillary line.
There are several skinfold sites available for measurement. Some common sites include the biceps, triceps, iliac crest, thigh, calf, subscapular, abdomen, and chest. The exact technique can vary, but we will discuss one method using the triceps as an example. For the triceps skinfold, grab the skin 2 cm above the midpoint of the right upper arm with the thumb and index finger to create a skinfold, then place the calipers at the midpoint. The rest of the common sites can be measured similarly by grabbing the skin 2 cm away from the measuring site.
The BMI calculation is the weight in kilograms, divided by the height in meters squared.
There are very few complications as a direct result of anthropometric measurements. One possible complication is an error in measurements. There is evidence suggesting an error in weight and abdominal obesity measurements occurs in higher proportions in the obese population. This is possibly due to difficulty assessing bony landmarks in obese patients. Another common cause of measurement error is obtaining measurements in a non-uniform manner.
Anthropometric measurements have utility in assessing physical fitness data for a wide variety of the population, from children to elite athletes to the elderly. These measurements, including height, weight, circumferences, and skin folds, can be used either as a baseline or as a marker of progress. One study of Australian volleyball players revealed that anthropometric data improves with increases in playing level. Another study used anthropometric measurements as a marker of physical fitness progress in women age 60-100. They found that pilates combined with hydrogymnastics decreased BMI, weight, and hip and waist measurements.
Since obesity is a major modifiable risk factor of cardiovascular disease, stroke, diabetes mellitus, dyslipidemia, and hypertension, one of the best clinical utilities of anthropometric data is to define obesity. The best measurement to define obesity is not uniformly agreed upon, as is illustrated by one study which compared BMI, waist circumference, waist-to-hip ratio, and waist-to-height ratio. This study found that there is not adequate evidence to support one method of measurement over any other, but states BMI is the most logical choice given its historical use. The authors also demonstrated that elevations in anthropometric measurements led to a higher odds ratio of dyslipidemia, hypertension, and hyperglycemia.
The lengths of extremities are related to chronic diseases as well. A literature review shows that those with a shorter upper leg length (ULL) have a higher prevalence of metabolic syndrome. Similarly, shorter upper arm length has an association with a higher prevalence of diabetes in Japanese Americans.
While anthropometric data in the adult population is helpful to define obesity, it is also used extensively in the pediatric population to determine nutritional status. By measuring the height for age, weight for age, and weight for height, it can be determined if children are stunted, underweight, or wasting, respectively. Once any of these conditions are determined, the practitioner should consider replacing nutrients, secondary causes of the condition, and a potential referral to a dietitian. Head circumference is another anthropometric measurement routinely used in children. This measurement is important to diagnose microcephaly, which has well-documented complications. Another anthropometric measurement useful to assess nutritional status in children is mid-upper arm circumference (MUAC), which can be used to define the severity of malnutrition. MUAC also has utility to assess nutritional status in the pregnant population as one study showed MUAC is the anthropometric measurement of choice in pregnancy.
Although technology may eventually advance to replace anthropometry on some level, one study found that the anthropometric measures of waist and hip circumferences are superior to ultrasound to assess for regional adiposity. Regional adiposity is critical in defining metabolic syndrome, which is important to define because it has many complications, including cardiovascular disease, stroke, diabetes mellitus, and many others.
Enhancing Healthcare Team Outcomes
The best way to improve the outcomes of anthropometric data is to improve the accuracy of measurements. The most effective way to improve accuracy is always to follow the same uniform methods to obtain measurements. To enhance long-term patient outcomes, an interprofessional team consisting of nurses, nurse practitioners, physician assistants, and physicians should work together to consistently promote a healthy lifestyle for patients to avoid the well-documented adverse effects of obesity and malnutrition. [Level 5]