Total body electrical conductivity (TOBEC) analysis is a bioelectrical technique that uses measures total body electrical conductivity to estimate lean body mass. Other dimensions can also be assessed. The method was originally developed to quantify lean tissue in meat.
The TOBEC method is based on the principle that organisms placed in an electro-magnetic field perturb the field. The degree of perturbation is dependent on the amount and volume of distribution of electrolytes present. Fat free mass (FFM) has a much higher water and electrolyte content than fat mass (FM) and the strength of the field depends on the electrolytes found in the person's body water.
- The TOBEC instrument is a scanning device in which the participant moves on a motor-driven sled through a 2.5-MHz coil electromagnetic field at a constant rate.
- The participant passing through the electromagnetic field of the coil absorbs heat energy, thereby perturbing the electrical field of the coil. The loss of energy detected in the coil is an index of the conductive mass of the body.
- For adults, the whole body is scanned, and information is collected at 64 positions along the length of the body. The length of an infant's body is sufficiently short that a static measurement can be made; that is, if the outer coils are about twice the length of the body, then the infant can be placed at the center of the coils for the measurement.
- Each assessment takes approximately 40 seconds.
- The electrical conductivity of the participant is summarised by the an output referred to as the TOBEC number'.
Participant instructions
- Participants should remove shoes, jewelry, and clothing containing metals
- Participant should be fasted
- Participant bladder should be empty
- Participant should not be under or over hydrated
- Clothing should be dry
This method is most accurate when measuring lean mass. However, it is not widely available and expensive to purchase.
TOBEC has been used mainly to monitor changes in body composition in women during pregnancy or lactation, in infants and in childhood obesity.
- The human body is approximated by a cylinder of volume (V) and length (L)
- It is assumed that V is directly proportional to: (E×L)1/2, where E is a variable called the “TOBEC number” provided by the instrument
- The conduction volume is assumed to be the body's total electrolyte volume
- Thus the TOBEC instrument has been calibrated with a measurement of TBW
An overview of the characteristics of TOBEC is outlined in Table 1.
Strengths
- Compares favorably against underwater weighing, and deuterium dilution, particularly for fat free mass
- It is easy to use and requires no preparation from the participant
Limitations
- It can be affected by hydration status
- Has a high cost
- Not widely available
- It is based on regression equations for the estimation of TBW, FFM and FM
Table 1 Characteristics of TOBEC.
| Consideration | Comment |
|---|---|
| Number of participants | Small |
| Relative cost | High |
| Participant burden | Low |
| Researcher burden of data collection | Low |
| Researcher burden of coding and data analysis | Low |
| Risk of reactivity bias | No |
| Risk of recall bias | No |
| Risk of social desirability bias | No |
| Risk of observer bias | Yes |
| Space required | High |
| Availability | Low |
| Suitability for field use | Not suitable |
| Participant literacy required | No |
| Cognitively demanding | No |
Considerations relating to the use of TOBEC in specific populations are described in Table 2.
Table 2 Use of TOBEC in different populations.
| Population | Comment |
|---|---|
| Pregnancy | Yes* |
| Infancy and lactation | Yes* |
| Toddlers and young children | Yes* |
| Adolescents | Yes |
| Adults | Yes |
| Older Adults | Yes |
| Other (obesity) | Yes* |
*TOBEC has been used mainly to monitor changes in body composition in women during pregnancy or lactation, in infants and in childhood obesity.
Refer to section: practical considerations for objective anthropometry
- TOBEC scanning equipment
- Sufficient space to house the TOBEC scanner
- Trained operator
References
- Boileau RA: Utilization of Total Body Electrical Conductivity in Determining Body Composition. In: Designing Foods: Animal Product Options in the Marketplace. Washington, National Academies Press (US); 1988
- Baumgartner RN: Electrical impedance and total body electrical conductivity. In Human Body Composition, editors: Roche AF, Heymsfield SB, Lohman TG (Human Kinetics, Champaign, Illinois) 1996
- Butte NF, Hopkinson JM, Ellis KJ, Wong WW, Smith EO: Changes in fat-free mass and fat mass in postpartum women: a comparison of body composition models. Int J Obesity Related Metabolic Disorders 1997: 21; 874
- Cochran WJ, Klish WJ, Wong WW, Klein PD: Total body electrical conductivity used to determine body composition in infants. Pediatric Research 1986: 20; 561
- Cochran WJ, Fiorotto ML, Sheng HP, Klish WJ: Reliability of fat-free mass estimates derived from total body electrical conductivity measurements as influenced by changes in extracellular fluid volume. Am J Clin Nutr 1989: 49;29
- Ellis KJ: Measuring body fatness in children and young adults: comparison of bioelectrical impedance analysis, total body electrical conductivity, and dual-energy X-ray absorptiometry. Int J Obesity 1996: 20; 866
- Fiorotto ML, Cochran WJ, Klish WJ: Fat-free mass and total body water of infants estimated from total body electrical conductivity. Pediatric Res 1987: 22; 417
- Heyward VH: Advanced Fitness Assessment & Exercise Prescription. 2nd ed. Champagne, Illinois: Human Kinetics; 1991
- Heymsfield S, Ross R, Wang Z, Frager D: 5 - Imaging Techniques of Body Composition: Advantages of Measurement and New Uses. In: Emerging Technologies for Nutrition Research: Potential for Assessing Military Performance Capability; Institute of Medicine (US) Committee on Military Nutrition Research; Carlson-Newberry SJ, Costello RB, editors. Washington (DC): National Academies Press (US); 1997
- McArdle WD, Katch FI, Katch VL: Essentials of Exercise Physiology. 3rd ed. Philadelphia: Lippincott Williams & Wilkins; 2006
- Motil KJ, Sheng HP, Kertz BL, Montandon CM, Ellis KJ: Lean body mass of well-nourished women is preserved during lactation Am J Clin Nutr 1998: 67; 292
- Norgan NG: Laboratory and field measurements of body composition Public Health Nutrition 2005: 8; 1108