Facts on Obesity

The health risks associated with obesity are clear, as are the related costs. New estimates by the National Institutes of Health report that obesity related costs are approaching $100 billion per year in the US alone¹. Based on new obesity guidelines established by the NIH, an astounding 54.9 of the American adult population is either overweight or obese². The UK reports that over 50 of its adult population is considered to be overweight. Many obesity experts feel that obesity has reached epidemic status on a worldwide stage. 

The NIH report states "Obesity is clearly associated with increased morbidity and mortality³. "Individuals identified as obese have increased risk of developing Type II diabetes, coronary heart disease, stroke, certain cancers, osteoarthritis, sleep apnea, and other serious illnesses. Males and females In the highest obesity category have 5 times the risk of hypertension and high blood cholesterol compared to normal weight individuals. After smoking, obesity is the second leading cause of preventable death in the United States⁴. 

Obesity Guidelines

The NIH has updated the United States' classification of overweight and obese individuals. The new guidelines bring the US in line with most other obesity classification systems in the world. Body Mass Index (BMI) is generally accepted around the world as a screening tool for obesity. The new guidelines announced by the NIH are as follows.

Facts - Continued

Because of staggering human and economic costs, there is more attention being directed towards obesity within governmental, medical and pharmaceutical communities. However, despite recent announcements adding to the body of research detailing the health risks of obesity, physician and public awareness continues to be limited. Tanita joins with those agencies that continue to provide responsible information to both the professional community, and the public. 

Classification of Overweight and Obese

Tanita welcomes these new guidelines as a more effective obesity screening tool. It is our hope that these guidelines will enable professionals to better recognize and understand obesity-related issues such as proper weight management, responsible diet, and long term behavior modification.

BMI and Body Composition

Body Mass Index is a calculation that interprets body weight for individual differences in stature (Weight (kg) / Height (m2), and correlates this index to mortality ratios. BMI is an effective screening tool for obesity, and the new guidelines provide further reason for its inclusion in a health screening. However, BMI was not designed to predict actual body composition^6.

Using a multifaceted approach to weight maintenance may provide more insightful Information than any one measurement technique alone. We strongly believe that incorporating body composition analysis along with BMI screening will provide a more complete measure of patient health over a long time period. In some cases, it is possible for an individual to lose weight, report a reduction in BMI, and yet increase their percent body fat. After an Initial determination of obesity through BMI screening, body composition analysis can provide more in-depth information regarding actual body composition. Regular assessment over time also allows for tracking shifts in fat and fat free mass, which may provide the client with a greater understanding of the unseen benefits of long-term behavioral changes.

Understanding BIA Technology

Tanita utilizes a patented "foot to foot" pressure contact electrode Bioelectrical Impedance Analysis technique⁷. The BIA technique is based on the fact that lean tissues have a high water and electrolyte content, and thus provide a good electrical pathway⁸. Fat mass contains a lower percentage of body water, and thus is a poor conductor of the electrical signal. By inducing a low energy, high frequency, electrical signal (50 kHz, 500 micro amp), a measurement of the baseline resistance to the flow of electrical current can be made. This current is passed through the anterior electrode on the scale platform, and the voltage drop is then measured on the posterior electrode. The measurement relates directly to the volume of the conductor, which is used to determine total body water, lean body mass, and finally, fat mass. Percent body fat, as calculated by Tanita, is a highly researched proprietary formula combining impedance and weight measurements with height, gender, and age information.

Proper Protocol

In order to obtain the most accurate results from your Tanita Body Analyzer, please ensure the following conditions are met⁹:

• No alcohol 48 hours before the test

• Avoid intense exercise 12 hours before the test

• Avoid eating or drinking (especially coffee, tea, and colas) 4 hours before the test

• Empty bladder 30 minutes before test

• Avoid all diuretics for 7 days before test (only if possible)

Measure in bare feet. Individuals wearing thin nylons will receive accurate results if a drop of liquid (saline solution, water) is placed in the center of each electrode. Test should be taken 3 hours after waking. Illness at the time of measurement may affect individual hydration levels, which may affect results.

Tanita BIA and Reproducibility

Generally speaking, the impedance value will increase when dehydration is present. Conversely, if weight increases due to excessive fluid intake, impedance values will decrease. Water and electrolytes act as conductants for the mild electrical current, which is passed through the body. When this "pathway" is disturbed, the resulting impedance value will reflect the change¹⁰.

Ensuring reproducible results is essential when making long-term body composition assessments. In order to attain the best possible results using any BIA equipment, consistency in the measurement protocol is necessary. Inaccurate results are often due to inconsistent measurement conditions such as those that affect internal hydration levels. Under normal conditions, total body water (TEW) accounts for 55-65% of body weight, depending on the individual's physical condition, gender, and hydration status¹¹. While Tanita body composition products do not directly measure total body water, TEW plays an important role with respect to BIA technology. Large changes in TEW will cause a change in impedance, which will in turn affect fat mass as read by Tanita.

Within - a - day Variation

Much like blood pressure, hydration status fluctuates throughout the day¹². The normal hydration cycle is as follows. During sleep, extra cellular fluid and blood move away from the extremities, and tend to gravitate toward the internal organs. This may result in an Increased impedance reading. While awake, blood and extra cellular fluid circulate throughout the body, effectively hydrating the extremities. This may be the best time to measure a subject. The daily hydration cycle can also be affected by diet, other shifts in fluid distribution, or dramatic changes in sleep cycle¹³.

The largest change in impedance due to daily hydration fluctuations can be observed over the first 3 to 4 hours after waking¹⁴. Again, this is typically when blood and extra cellular body water begin to circulate more actively to the extremities.

Day-to-Day Variation

As part of any normal weight maintenance or exercise program, body composition may be assessed weekly. Most short-term changes are simply day-to-day variations¹⁵. Long-term results can be reliably measured at 3-4 week intervals. Measuring at appropriate intervals will help you avoid potentially confusing or even conflicting results, and more importantly may serve to reinforce positive long-term behavior modification.

Conclusion: Taking measurement at the same time of day should yield optimal results. If consistent test conditions are maintained, results will be consistent and reproducible.

Many successful weight loss/maintenance programs rely on long-term commitment and motivation. Measuring body composition consistently over a period of several months may provide helpful insight to the progression of a program. Tanita believes that trending over a long time period is the most effective way to incorporate body composition analysis in a health assessment, or weight management environment.

 References

1 National institute of Health: National Heart. Lung, and Blood Institute, Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence Report (1998) 9.

2 National Institute of Health: National Heart, Lung, and Blood Institute.

3 National Institute of Health: National Heart, Lung, and Blood Institute.

4 National Institute of Health. National Heart. Lung, and Blood Institute.

5 National Institute of Health: National Heart, Lung, and Blood Institute.

6 Dympna Gallagher, Marjolein Visser. Dennis Sepulveda, Richard N. Pierson, Tamara Harris, and Steven B Heymesfield, "How Useful Is Body Mass Index for Comparison of Body Fatness across Age, Sex, and Ethnic Groups?^" American Journal of Epidemiology. 3rd ser. 143(1996): 228-239

7 C Nunez, D Gallagher, M. Visser, F.X. Pi-Sunyer, Z. Wang, and S.B. Heymsfield. "Bioimpedance analysis: evaluation of leg-to-leg system based on pressure contact foot-pad electrodes. Med. Sci. Sports Exerc. 4th ser. 29 (1997): 524

8 Vivian H Heyward, "Evaluation of Body Composition", Sports Medicine 3rd ser. 22(1996); 146-56

9 Vivian H. Heyward and Lisa M. Stolarczyk, Applied Body Composition Assessment, (Champaign: Human Kinetics, 1996)54.

10 Vivian H. Heyward and Lisa M Stolarczyk, Applied Body Composition Assessment, (Champaign; Human Kinetics, 1996) 52

11 Rodney Rhodes and Richard Pfanzer, Human Physiology. (Saunders College Publishing: Orlando: Harcourt Brace Jovanovich, 1992) 858.

12 Heyward and Stolarczyk, 51

13 National Institute of Health: Bioelectrical impedance analysis in body composition measurement: National Institute of Health Technology Assessment Conference Statement. December 12-14 1994

14 National Institute of Health

15 National Institute of Health

16 Heyward, 146-56

17 C Nunez, J. Beyer, G. Strain, B. Zumoff, A Kovera, D. Gallagher Et S. B. Heymsfieid. "Composition of Weight Loss While Dieting: Comparison of Research and Clinically-Based Methods", Poster, Cancun, Mexico, 1997, NASSO Meeting (1997).

18 National Institute of Health

Source: Information Report Supplied By Tanita

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Body Composition Analysis: Trending vs. Research

The only 100% accurate method of direct body composition measurement available today is direct clinical analysis of tissues. All current body composition assessment methods rely on indirect measurement techniques to estimate body fat, fat free mass, and other commonly reported data¹⁶. This includes simple methods such as skin fold calipers, as well as the most sophisticated research techniques available today (i.e. DXA, hydrostatic weighing tanks. Magnetic Resonance Imaging, and other methods). All body composition equipment manufacturers should have scientific studies available to support accuracy claims, but most fail to explain the problems encountered in day-to-day use outside of the controlled environment of a research laboratory. We at Tanita believe it is very important for our customers to fully understand the benefits, and limitations, of body composition analysis. By so doing, we think you will be better prepared to make educated decisions based on results, and thus pass better information to your clients.

While there are numerous reasons to do body composition analysis, the two most common are research and health assessment. While research facilities expect their subjects to follow strict protocols before, during, and after testing, facilities in the "real world" usually cannot attain the same level of compliance. Tanita recommends a well-established BIA protocol for accurate testing. When these standard guidelines are followed, the absolute value reported correlates highly with accepted research methodologies (DXA, Hydrostatic Weighing)¹⁷. Tanita encourages practitioners to follow the established protocol in order to obtain the most accurate absolute values.

However, situations may arise where individuals cannot be expected to adhere to every pre-test condition. In such cases, it is important to know that reliable trending results are still possible. The crucial step in obtaining accurate trending results is maintaining consistent conditions. In other words, consistent pretest behavior should yield reliable results.

Consistent Conditions Provide Consistent Results

Helping clients understand the notion of trending over time may reinforce the long-term goals of proper weight therapy. Because trending over time is critical, the client must understand the need for consistent behavior. For example, if an individual can only be tested early in the morning, schedule subsequent tests for approximately the same time, preferably no earlier than 3-4 weeks from the initial test. While the absolute value of percent body fat may be slightly altered due to an abnormal hydration state, the skew should be consistent in subsequent tests. In other words, observed change should reflect actual patient status.

Tanita strongly recommends that facilities encourage participants to follow the established guidelines, however, when this is not possible, testing at the same time of day, at 3 - 4 week intervals, should ensure a high level of reproducibility over time. Consistent daily behavior normally yields a regular hydration cycle, which then provides a basis for consistent trending results¹⁸.