Written by: Michelle Rockwell, MS, RD, CSSD, Virginia Polytechnic Institute and State University

Body composition is a physical measurement that provides more specific information about body make-up than body weight alone. Body composition can be defined as the proportion of fat and fat free mass (FFM) in the body. Fat free mass includes primarily muscle, bone, and water along with some other elements. Fat mass includes fat that is stored as an energy source and fat in the central nervous system, organs, bone marrow and sex tissues, known as essential fat.

Body composition is typically expressed as percent body fat and pounds of FFM. For example, a student-athlete who weighs 180 pounds may have a body composition of 15 percent body fat and 153 pounds of FFM. This means that this athlete has approximately 27 pounds of body fat. If, after training and nutrition intervention, this athlete gains 3pounds., to 183 pounds, with a body composition of 13 percent body fat and FFM of 160 pounds, the athlete has demonstrated an improved body composition. This athlete lost 3 pounds of fat and gained 7 pounds of lean tissue, presumably muscle.

Does body composition impact athletic performance and health?

Body composition and weight should be viewed as the outcome of a well-executed fueling and training plan. Results are best utilized to track student-athlete lifestyle habits over time, and to prioritize individual nutrition strategies. Many elite athletes can easily fit into recommended ranges for their sport, but lifestyle habits are not optimized. Others may fall into the extremes, either over or under the typical ranges for their sport. Regardless, developing optimal fueling, training, rest and recovery habits should be priorities for all student-athletes, in order to optimize performance and long-term health.

Many student-athletes have goals of gaining or losing weight. Some perceive direct performance benefits, some have aesthetic reasons while others are meeting the necessary weight requirements of their sport (e.g. wrestling and rowing.) Student-athletes benefit from focusing on altering body composition more than just weight alone. Losing body fat while maintaining or increasing FFM is typically favorable in sports. When the focus is limited to scale weight, improper fueling becomes more likely as does the risk of losing lean tissue, bone mass or energy stores and gaining undesirable fat stores. Improper fueling can relate to increased illness and injury risk, poor recovery, decreased performance and more.

Body composition targets

It is common for student-athletes to seek out a body composition goal or to ask “is my body fat too high?” or “what’s right for my sport?” It is strongly recommended that each student-athlete be evaluated individually for a target range ideal for them. This should always be accompanied by education and counseling that different body types exist and succeed in different sports and that it is impossible to make a one-size-fits-all recommendation. Determining an individual target range may incorporate questions such as what was the student-athlete’s body composition when she or he felt best? Performed best? What would reflect a realistic rate of change? What would allow the athlete to make important lifestyle changes that are realistic for her/him?

Student-athletes may be familiar with the recommended healthy body fat range for adult males (10-22 percent) and females (20-32 percent). As noted, different healthy ranges suit different individuals and lower (or even higher) could be appropriate for student-athletes, but these numbers may serve as valuable reference points. It is important to keep in mind that these values are based on skinfold caliper analysis; they are not applicable to other testing methods (DEXA, Bod Pod, etc.) which yield different results. Student-athletes should avoid extremely low body fat, which can be associated with impaired physiological function in both males and females². It is commonly suggested that 5 percent body fat for men and 12 percent for women are the minimum required for healthy endocrine and immune function. (The International Society for the Advancement of Kinanthropometry suggests a minimum of sum of 7 skinfolds of 30-60mm for men and 40-90 mm for women.)³ Note that the red flag number is higher for some athletes and lower for others and it is equally as important to monitor trends in body composition. A student-athlete with a higher body fat who drops a significant amount in a short time is at the same risk.

Table 1 shows body composition ranges typical for collegiate student-athletes, based on skinfold caliper analysis. These values should not be taken as recommendations or strict guidelines. Rather, they should be used as a reference point when evaluating body composition results. Every student-athlete is different and the recommended range for any specific individual may or may not fall within the range. Table 2 shows compiled bod pod results from the 2006 to 2013 NFL combine. Note the variability of body composition by position played and also within each category. For example, running backs averaged 11.8 percent body fat, but the range reported for that position was 4 to 23 percent.⁴

Table 1. Common body fat percentages of college student-athletes²

Sport	Male	Female
Baseball	12-15%	12-18%
Basketball	6-12%	20-27%
Football (Backs)	9-12%	No data
Football (Linemen)	15-19%	No data
Gymnastics	5-12%	10-16%
High/long Jumpers	7-12%	10-18%
Ice/field Hockey	8-15%	12-18%
Distance running	5-11%	10-15%
Rowing	6-14%	12-18%
Shot Putters	16-20%	20-28%
Sprinters	8-10%	12-20%
Soccer	10-18%	13-18%
Swimming	9-12%	14-24%
Tennis	12-16%	16-24%
Volleyball	11-14%	16-25%
Wrestlers	5-16%	No data

Table 2. 2006 - 2013 NFL Combine testing (BodPod)

Position	# of Players	% Fat Average	% Fat Range	Body Weight Average (lb)	Body Weigh Range (lb)
DB	463	9.7	3.4 – 19.4	199.8	168.9 -238.8
WO	360	9.4	3.7 – 19.4	202.6	149.3 – 240.3
LB	270	13.5	4.0 – 22.5	239.3	203.1 – 269.5
TE	147	14.2	5.6 – 20.7	252.6	225.9 – 271.3
RB	263	11.8	4.0 – 23.1	217.1	168.3 – 260.5
QB	159	14.3	4.0 – 22.7	223.4	187.8 – 264.6
DL	445	19.4	3.8 – 34.2	283.2	221.3 – 368.6
OL	420	24.6	13.9 – 35.6	313.0	280.0 – 364.2
PK	86	15.9	3.8 – 30.5	206.6	170.6 – 253.1
ST	15	20.2	12.2 – 26.5	242.6	166.9 – 264.5

 

As a greater rate of obesity, disordered eating and associated health problems are seen at the collegiate level, appropriate attention must also be paid to interventions for student-athletes above and below their target body composition range. Working with a registered dietitian, particularly a board certified specialist in sports dietetics (CSSD) to design a nutrition plan is recommended.  

Assessing body composition

There are many different methods for evaluating body composition. There is no gold standard since some degree of estimation and error is associated with all methods.

Regardless of measurement tool chosen, if any, it is important that student-athletes be educated on the concept of body composition. Understanding that body weight does not tell the whole story, that you can’t see positive body composition changes on the scale, etc. is extremely valuable.

Assessment tools and methods used with college student-athletes:

In the collegiate setting, numerous assessment tools are used. Skinfold calipers are common, accessible, inexpensive, and thus, commonly used. The consistency and accuracy of results is highly dependent upon the individual conducting the assessment. Other athletics programs take tester variability out of the equation by using dual-energy X-ray absorptiometry (DEXA/iDXA) and Bod Pod to assess body composition. Each of these methods has strengths and considerations for student-athletes and testers. See Table 3for more information about various testing methods.

Considerations about body composition analysis:

• A body composition measurement from one method cannot be compared to one from another. For example, a football player evaluated by DEXA at his university cannot compare results to the BodPod values he receives at the NFL combine. Likewise, when tester or equipment variation comes into play, results also cannot be compared. A cross country runner who has skinfold caliper measurements performed by her strength and conditioning coach cannot compare results to the same measurements taken by the sports dietitian. Measuring via the same method in a systematic way offers the most benefit for individuals and team analysis.
• Measurements should be done in private. Results should be handled with sensitivity. The National Athletic Trainers Association suggests that body composition results be treated the same as other medical information with regard to confidentiality.
• Measurements should be taken when student-athletes are well-hydrated and before exercise.
• In general, measurements should be taken no more frequently than every two to three months. Some professionals recommend twice per year or less. Defer to your sports dietitian regarding specific student-athlete protocols.
• The management of body composition data should be informed by your staff’s philosophy of student-athlete development and must be consistent with the educational messages to the student-athlete. There should always be a purpose for taking measurement. Clear and consistent communication is paramount. Testers must be sensitive to the impact of assessment on student-athletes. If resources are not available to assist with the management of body composition information and education, its best to avoid it altogether. If you can’t manage it, don’t test it!
• Nutrition strategies and training programs should utilize body composition data in addition to other vital input such as medical history and status, performance measures, emotional well-being and the student-athlete’s goals.

Communicating about body composition

• Always emphasize performance measures, overall training, diet and healthy lifestyle as highest priority for athletes.
• When body composition change is appropriate, establish a percent body fat range rather than an absolute value.
• Changes in body composition should be gradual and targeted changes are priority in the off-season whenever possible.
• Guide student-athletes to focus on FFM as much as they focus on percent body fat as this is functional, powerful athletic tissue they wish to maintain or increase and can feel more positive than focusing on decreasing percent body fat.
• It is recommended that athletics departments develop guidelines and protocol for measurement, analysis and communication of body composition data.

Body composition can be very powerful tool for enhancing performance and well-being and tracking changes when careful consideration is made regarding procedures, data interpretation, and communication. Work with a sports RD to establish a body composition protocol that suits your student-athletes and staff.

Table 3. Various methods of measuring body composition

Testing Mode	% error	How it Works	Considerations
Skinfold Calipers	+3%	Hand-held calipers used to measure subcutaneous fat in specified	Inexpensive Reliability and accuracy highly dependent on experience and skill of tester Quick Many published norms, data, and recommendations using this method which aids in comparisons. May feel intrusive to some athletes.
Bod Pod (Air displacement plethysmography)	+2-3.5%	Determines body volume through air displacement analysis. Body composition then estimated using equations.	Expensive Test is fairly quick (about 10 min) Athletes have to wear swimsuit or minimal tight clothing and cap – privacy required Must be housed in environmentally appropriate and stable room.
DEXA	+1.5%	Body scan applying interpretation of different xray properties of bone and soft tissue.	Expensive Requires trained and potentially licensed administrator Highly accurate for many athletes Can also provide bone density measurements Limited to 4 or fewer scans per year due to radiation exposure
Hydrostatic weighing	+2.5%	Based upon Archimedes Principle which states that the buoyant force on a submerged object is equal to the weight of the fluid that is displaced by the object. Lean tissue is more dense than water, and fat tissue is less dense than water (muscle sinks, fat floats). Athlete with higher body fat will weigh less underwater and athlete with more lean tissue will weigh more.	Infrequently used; Very time-consuming Accuracy poor in many athletic populations
Bioelectric impedance	+3.5-5%	Relies on concept that lean and fat tissues have different conductive properties as a small current is passed through the body.	Relatively Inexpensive Quick and easy to perform; tester requires little/no training Results impacted by hydration status; hydration variability inevitable in athletes. Accuracy poor; not recommended for measuring changes in athletes’ body composition
Ultrasound	?	Small sonar device that utilizes high-frequency sound waves to produce images of body tissues; fat can be distinguished from other tissue.	Not yet common method of testing. More likely in research setting. High accuracy and precision Tester must be specially trained Much less expensive than MRI and CT Measures only subcutaneous fat; procedures for visceral and intramuscular fat being refined More research underway to better assess value and application in sports
MRI/CT	?	Uses imaging technology to estimate fat/lean mass from tissue area	Expensive Exposure to radiation Lack of normative and comparison data More research underway to better assess value and application in sports

Summarized from reference 2, Ackland et al.

 

References:

1. Thompson W. ACSM’s Guidelines for Exercise Testing and Prescription, 8^thPhiladelphia, PA: Lippincott Williams & Wilkins, 2010.
2. Ackland T, Lohman T, Sundgot-Borgen J, Maughan R, Meyer N, Stewart A, Wolfram M. “Current Assessment of Body Composition in Sport.” Sports Med. 2012; 42(3): 227-249.
3. Turocy PS, DePalma B, Horswill C, Laquale K, Martin T, Perry A, Somova M, Utter A. “National Athletic Trainers’ Association Position Statement: Safe Weight Loss and Maintenance Practices in Sport and Exercise.” J Athletic Training. 2011:46(3):322-336.
4. Moon J, Tobkin S, Smith A, Lockwood C, Walter A, Cramer J, Beck T, Stout J. “Anthropometric Estimations of Percent Body Fat in NCAA Division I Female Athletes: A 4-Compartment Model Validation.” J Str Cond Res. 2009:23(4):1069-79.
5. “Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition for Athletic Performance”. J Am Diet Assoc. 2009; 109: 509-527.

Written by SCAN/CPSDA Registered Dietitians (RDs). For advice on customizing an eating plan that includes a caffeine dosing protocol that is safe and based on current evidence, consult an RD who specializes in sports, particularly a Board Certified Specialist in Sports Dietetics (CSSD). Find a SCAN RD at www.scandpg.org

About Michelle Rockwell

Michelle Rockwell is a Registered Dietitian and Certified Specialist in Sports Dietetics with a private practice based in Blacksburg, Virginia. Michelle is the dietetics and graduate program coordinator at Virginia Polytechnic Institute and State University. She specializes in sports nutrition, eating disorders, and weight/chronic disease management in athletes of all levels. Michelle served as founding Sports Dietitian for the University of Florida and North Carolina State Athletic departments. She has also consulted with over 50 colleges and professional sports teams over the past 10 years. Michelle continues to teach and develop educational resources for developing Sports Dietitians. Her passion for sports nutrition manifested during her athletic career at Virginia Tech, where she was 5-time conference champion for the Track & Field team. www.michellerockwellRD.com