Consumer Bioelectrical Impedance Analysis Devices: What to know before you buy

By Kelly Hood

With the rise of home health electronics, many people own a bioelectrical impedance analysis (BIA) scale or handheld device to monitor body composition at home. Commercial BIA devices provide a relatively simple, inexpensive, and noninvasive technique to measure body composition. BIA devices work by sending a very low, safe electrical signal through regions of the body between plate electrodes; BIA scales do this through the feet whereas handheld devices go through the arms. The electrical signal passes quickly through water that is present in hydrated muscle tissue, but it meets resistance when it contacts fat tissue. The resistance, known as impedance, is measured and input into equations to calculate body composition, hydration status, and even bone density. Taking the measurement is easy, quick, and painless – but are the results accurate compared to industry gold standards?

Commercial BIA devices differ from one another in a variety of ways including body segments utilized for analysis, electrode contact points, body fat prediction equations, and cost.

Consequently, they can vary in their reliability and validity for different populations. For example, BIA scales only send a current through your feet and into your legs, missing out on a large portion of your body. Similarly, handheld devices only send a current through your hands and across your arms and chest. This can lead to over or underestimation of body fat, depending on one’s body type and gender. Also, depending on the specific equations used by each BIA scale, body fat results may not be as accurate for certain populations. Not all equations are the best fit for specific ethnic groups or body sizes, and most consumer devices use proprietary equations and do not directly display measured impedance.

A recent study conducted at San Francisco State University found that a consumer BIA scale had an error of ± 4.4% when compared to the industry gold standard of hydrostatic weighing. In addition, the scale underestimated body fat in males by an average of 2%. The consumer scale was found to be incredibly reliable both between days and between weeks, suggesting it is a reliable at home device. Further research needs to be done to investigate how sensitive it is to tracking changes in body composition. It is likely that the underestimation of male participants was due to gender differences in fat distribution. Males more commonly carry fat around the abdomen, which the foot-to-foot BIA scale used in the study may not have adequately registered. Alternatively, the specific equation used in the scale may not have sufficiently accounted for the fat distribution in males. Current research agreed with the study findings, revealing that BIA devices typically have a larger error range, ±3.5-4%, and become less accurate in individuals with higher BMIs. Additionally, hydration status of the individual can affect the measurement. To account for this and to ensure the most accurate results when tracking body composition over time, measurements should be taken at the same time of day under similar conditions. Thus, the accuracy of body fat measurements using regional BIA devices should be interpreted with caution.

To make better use of an at home BIA device, consider occasionally having your body composition assessed using hydrostatic weighing. This industry gold standard method for measuring body fat percent, with an error of ±1-2%, costs around $50 per test. Testing requires a trained technician and can be found at certain fitness clubs or local universities, including San Francisco State University. Measurements from gold standard methods will give a more accurate portrayal of your body composition, and an idea of how far off an at home BIA scale is for future use. The results from body composition testing can be used to identify health risks, personalize your exercise program or evaluate how well your current exercise and nutrition program is working for you, so it is important they are accurate.


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About the Author:

Kelly graduated with a double Bachelor of Science in Exercise Biology and Psychology from University of California at Davis. She recently completed her Master of Science in Exercise Physiology at San Francisco State University, where she conducted body composition research for her Master’s thesis. Kelly joined the BaySport Preventive team in 2015 to assist in the San Francisco Preventive Medicine Clinic and at biometric screening events across the bay. She is an avid runner, recreationally running marathons and local trail races across the bay. In her free time she enjoys, rock climbing, yoga, and exploring the great outdoors.

BaySport’s Healthy Holiday Challenge: Finding balance during the holidays

By Giselle BirangGilead Scale

Every holiday season, millions of Americans ring in the New Year with a common goal: weight loss. Waiting until after the holidays when many
people overindulge is challenging and can often cause frustration. The goal
of health and weight loss is to find balance and the Healthy Holiday
Challenge is designed for just that.

The Healthy Holiday Challenge is an eight week program designed for
employees to maintain and not gain over the holiday season; bringing in the New Year on a positive note. Employees form a team of four (individual participants are welcome) and weigh in as a group.

With three weigh-ins (initial, mid-point, and final), weekly informative emails, and team member support, each team’s goal is to maintain their initial weight throughout the eight weeks. Prizes are awarded at the end of the challenge to the teams that maintained and or lost weight.

Each week has a different health focus so as not to overwhelm the participants. One week can focus on mindfulness and relaxation, while another week focuses on exercise and healthy meal swaps.

This fun and free employee resource is used as a wellness tool for education, motivation and accountability. It helps the employees stay focused throughout the holiday season so they are not overwhelmed come the New Year. This challenge makes a healthy lifestyle attainable with the access to education and support from the Wellness Department.

Health is about balance. It’s a lifestyle that needs to be maintained and the Healthy Holiday Challenge is a fun program that helps thousands of employees reach their goals, start the year off by feeling healthy and enables them to find that balance.

Using the S.M.A.R.T. Method to Reach Your Goal

goalAs we welcomed the start of a New Year on January 1st 2015, many of us made New Year’s resolutions. Most New Year’s resolutions are weight and health related. Perhaps this year your goal is to lose weight. Or you found yourself saying I am going to work out every day starting now! Have you ever asked yourself if your goal is realistic? Are you still working on your New Year’s resolution now?

March is National Nutrition month. What better time to re-evaluate your goal and see if your goal is fit for success? A good way to set a nutrition or wellness goal is using the S.M.A.R.T. goal method. Ask yourself these questions:

Is my goal:

For a goal to be effective, it must state what you specifically want to accomplish. Instead of saying, “I will exercise more.” A clear and specific goal would state, “I will exercise for 30 minutes on 4 days per week at the gym for the next month.” A strong S.M.A.R.T. goal will define what will be accomplished within a stated time frame.

For a goal to be measurable, the goal will clearly state when the objective is achieved. In the S.M.A.R.T. goal above, the objective is achieved after the individual has exercised for 30 minutes on 4 days out of the week.

An attainable goal is one that is achievable for the goal setter. S.M.A.R.T. goals are focused on long term lifestyle changes, which result from small, gradual behavior changes. If an individual is looking to decrease sodium in their diet, it may not be realistic to say they are going to never eat out again if they are currently eating their lunch from a restaurant every day. A more realistic goal may be to say, “I will pack a lower sodium lunch for work at least 3 out of 5 days per week to avoid eating at a restaurant every day.” And an even more specific way to state the same goal would be to say, “I will pack a sandwich made with whole grain bread, reduced sodium chicken breast, tomato, and lettuce, an apple, and milk at least 3 out of 5 days per week.”

Relevant goals are those that the individual actually wants to achieve. Often people decide they want to do something for the wrong reasons. A New Year’s resolution of losing weight is so common. Ask yourself, did I make this resolution because this is the goal that everyone is making? Do I really want to work on losing weight? Perhaps choosing a specific change in the diet such as eating a salad with dinner every other night is a more relevant goal? The bottom line, the goal needs to be something you want to do.

And the last quality of an effective S.M.A.R.T. goal is having a time-frame or, in other words, a beginning and an ending date. This makes the goal feel time bound. At the end of the stated end date, the individual can feel accomplished and worthy of an award. A month is a wise time frame for most goals since that is the length of time it takes to establish a habit (Pavlina, 2005). Once the month has passed the individual can decide if they would like to re-establish the goal if it was successful or restate the goal if it was not accomplished.

Academy of Nutrition & Dietetics
Health Guide
Pavlina, S. (2005, 14 April). 30 Days to Success. Personal Development for Smart People. Retrieved 4 June, 2010 from –

About the Author:
Sheri Berger is a Registered Dietitian having completed her B.S. in Food/Nutrition & Dietetics and a dietetic internship at Loyola University Chicago. Sheri has a diverse professional background that includes hospital and outpatient clinic patient support, preventive wellness programs, corporate wellness services, cardiovascular disease management, and working with seniors. Sheri enjoys engaging her clients in pursuit of their personal wellness goals and leading by example with her healthy lifestyle. She has been certified in adult weight management since 2005. She belongs to the American Dietetic Association, California Dietetic Association, and the San Jose Peninsula District of the CDA. Sheri enjoys spending her free time with her husband and two daughters and she loves to run. This past September, Sheri completed her second half marathon, located in San Francisco.