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.


American College of Sports Medicine. Guidelines for Exercise Testing and Prescription. 9 th ed. Lippincott, Williams, and Wilkins, Baltimore, 2013.

Heymsfield, S.B., Wang, Z., Baumgartner, R.N., & Ross, R. (1997). Human body composition: advances in models and methods. Annual Review of Nutrition, 17: 527-58.

Fields, D.A., Goran, M.I., & McCrory, M.A. (2002). Body-composition assessment via air-displacement plethysmography in adults and children: a review. American Journal of Clinical Nutrition, 75: 453-467.

Peterson, J.T., Repovich, W.E.S., & Parascand, C.R. (2011). Accuracy of consumer grade bioelectrical impedance analysis devices compared to air displacement plethysmography. International Journal of Exercise Science, 4 (3): 176 -184.

Boneva-Asiova, Z. & Boyanov, M.A. (2008). Body composition analysis by leg-to-leg bioelectrical impedance and dual-energy X-ray absorptiometry in non-obese and obese individuals. Diabetes, Obesity, and Metabolism, 10 (11): 1012-1018.

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.

Guidelines for a Healthy New Year

By Giselle Birang

This year, move beyond the single statement resolution and form a list of actions. Consider the options below and commit to small daily changes. This can add up to long term healthy habits that can help you reach your goals; whatever they may be.

Here are tips for how to maintain your health year-round:

Sleep: Sleep is a time when the body recovers. Adequate sleep can benefit body weight, heart health, mental state and more. When sleep is limited, it can affect your health in a number of ways. According to the Mayo Clinic, “Numerous studies have found links between insufficient sleep and heart disease, heart attacks, diabetes and obesity.”

Do Now: Set a bedtime alarm to remind yourself to go to sleep and listen to it. Gradually alter it by 15 minute increments until you are achieving an hour more sleep a night.

Drink water: Water accounts for 60 percent of the body and is essential to every cell. Drinking water has many health benefits. According to WedMD, “Drinking water helps to maintain the balance of bodily fluids, energizes muscles, promotes clear and youthful skin and strengthens the body’s kidneys. WebMD states, “The number one cause of afternoon fatigue is dehydration.”

Do Now: Grab the bigger cup at the café and fill it with water in the morning at the same time as your coffee. Put it on your schedule to finish it at certain times throughout the day.

Eat well: Diet plays an integral role in managing health. What you eat can dictate how you feel, how well you sleep, your energy levels and your mood. According to WebMD, “A healthy diet gives your body the nutrients it needs to perform physically, maintain wellness and fight disease.”

Do Now: At a loss for what to cook? Sign up for four weeks of a meal delivery kit that serves healthful options. Once you’re used to cooking the meals they’ve prepared, you’ll have more ideas and more confidence to plan your own.

Move often: Similar to eating right, regular movement not only can help with weight control, mood and energy, but it is instrumental in combating disease. According to the Center for Disease Control, “Physical activity is one of the most important things you can do for your health. It can increase your chances of living longer and healthier.”

Do Now: Start or end each day with a 10 minute walk. Add 10 minute increments as you are able until you reach 30 minutes. Keep in mind, a brisk walk is more conducive than a slow stroll.

Take deep breaths: Shallow breathing is often a natural response to stress. Deep breathing promotes relaxation and stimulates blood flow to your organs. Alternatively, shallow breathing, often accompanied by stress, can suppress your immune system and leave you feeling anxious. According to Harvard Health Publications, “Deep abdominal breathing encourages full oxygen exchange — that is, the beneficial trade of incoming oxygen for outgoing carbon dioxide. This can slow the heartbeat and lower or stabilize blood

Do Now: Breathe in through your nose for a count of four, breathe out through your mouth for a count of six. Repeat this four times, three different times throughout the day.

Laugh: According to WebMD, laughter is thought to be similar to exercise. Dr. William Fry, professor of Psychology at Stanford University, California, claimed it took ten minutes on a rowing machine for his heart rate to reach the level it would be after just one minute of hearty laughter.

Do Now: Share something silly about yourself to a friend, attend a comedy show or listen to a comedy podcast.

Diabetes and Physical Activity

exerciseBy Sam Skelton

In the United States, 29.1 million people have diabetes (CDC, 2014). Think about that number for a second – that’s more than the total population of Australia. In 2012, 1.7 million people 20 years and older were diagnosed with Type 2 diabetes, which is where the body cannot use insulin properly. One in three adults are prediabetic. The risk of death for adults with diabetes is 50% higher than those without (Colberg, et al., 2010). These statistics are staggering. What can we do about this? The good news is that physical activity can help prevent and manage the health related complications from diabetes.

Exercise plays a major role in preventing and controlling insulin resistance (NIDDK, 2014). Both resistance training and cardiovascular exercise is recommended. Let’s get scientific here to learn why both types of training are beneficial. Cardiovascular training utilizes fat as an energy system, and fat oxidation is a key aspect of improved insulin action. A chronic effect of cardiovascular training results in greater insulin action via increased lipid storage in muscle and fat oxidation capacity, thus improving the blood glucose control in the diabetic exerciser (Colberg, et al., 2010).

Both cardiovascular exercise and resistance training require muscle contractions, and contracting muscles increase the uptake of blood glucose. While blood glucose levels are maintained by the glucose production in the liver, resistance training can especially assist in the muscular uptake of blood glucose. What is fascinating is that blood glucose uptake is normal when the muscles start working in a diabetic individual, where insulin-mediated uptake is usually impaired. To sum it up, an increase in muscle mass contributes to greater blood glucose uptake and thus enhances the blood glucose management for the diabetic exerciser (NIDDK, 2014).

A combination of both cardiovascular exercise and resistance training shows greater improvements in health complications from diabetes than either type of exercise alone. The take away here is to move every day (minimum of 10 min bouts; 150 min/wk) to the point where you are out of breath or not able to sing. At least twice a week (non-consecutive days), be sure to include resistance training into your workout routine. Perform 5-10 exercises involving all major muscle groups with three sets of 8-10 repetitions (Colberg, et al., 2010).


Centers for Disease Control. 2014 National Diabetes Statistics Report.

Colberg, et al. (2010). Exercise and Type 2 Diabetes. The American College of Sports Medicine and the American Diabetes Association: joint position statement. U.S. National Library of Medicine.

National Institute of Diabetes and Digestive and Kidney Diseases. Diabetes and Physical Activity. U.S. Department of Health and Human Services.

About the Author

Sam Skelton, B.S. Kinesiology

Sam is an ACSM Certified Exercise Physiologist and enjoys helping others attain a healthy lifestyle. Sam has been surfing since he was eight years old and raves about the “five waves a day program”. He also loves music and enjoys playing guitar in a punk rock band.

Most of all, Sam delights in spending time with his wife, Julie, and his sons Henry and Theodore. The Skelton’s love spending time outdoors; from the beaches of Santa Cruz, to the nearby mountains full of huge redwoods and sequoias.