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.

References:

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.

Keep Your Young Athlete in the Game: Health tips for developing athletes

Injuries

The most common reason adolescents drop out of sports is due to injury. Approximately 50% of injuries in young athletes are due to overuse injuries. Injuries at a young age that are not managed properly can discourage your child from participation in sport and exercise throughout their lifespan. To prevent overuse injuries:

  • Do not advise your child to “play-up” or play on a more advanced team. Even though their skills may warrant playing on a more advanced team, their body may not be mature enough to handle the stresses of advanced play.
  • Be sure to start with a dynamic warm up/stretch before participating in an activity to reduce injury risk.
  • Limit participation in “competitive” or “select” teams if your child is not skeletally mature. You should consult your pediatrician to determine your child’s ability to participate in a more advanced level of play.
Stress

Physical stress is not the only type of stress injuring young athletes. Student’s eagerness to please coaches, parents, and peers often leads to undue stress on their growing bodies. Some psychological and emotional factors you should take into consideration with young athletes include:

  • Young athletes often consider their sport as part of their identity.
  • They tend to be more focused on the present than the future.
  • Life issues such as sexuality, body image, grades, schoolwork, fear of failure or disappointing adults are some of the emotional stresses that affect their athletic ability.
Nutrition

It is imperative that young athletes receive proper nutrition. Knowing what, when, and how to eat and drink can help with development, performance, and injury prevention. A well balanced diet includes macronutrients (protein, carbohydrates, and fat) and micronutrients (vitamins and minerals) along with proper hydration.

  • Carbohydrates: simple, refined carbohydrates should be avoided; instead whole grains, vegetables, fruits, milk, and yogurt should be the primary carb source.
  • Proteins: lean meat, fish, eggs, dairy products, beans, and nuts are good sources of protein. Processed meats should be avoided. It should be noted that too much protein is hard on the liver, so it’s not the more the better when it comes to muscle gain.
  • Fat: necessary to absorb vitamins A, D, E, and K along with protecting organs and providing insulation. Good sources of fat include: lean meat, fish, nuts, full fat dairy products, and oils such as coconut or olive oil. Fats from chips, candy, fried foods, and baked goods should be minimized.
  • Calcium, Vitamin D, and Iron should be focused on when it comes to micronutrient intake for young athletes.
  • Young athletes need to monitor their fluid intake before, during, and after games and practices. The temperature outside and the activity being performed should be noted for making hydration adjustments.

Resources:

Purcell, Laura. (2013). Sport Nutrition for Young Athletes. NCBI. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3805623/

Johnson-Galvez, Tegan, D.P.T., C.C.I. (2011). Five Things You should Know About Your Young Athlete. BaySport Blog. http://baysport.com/baysportblog.html

Satiating Your Hunger and Quenching Thirst

By John Paul de Guzman

Have you ever felt hungry or thirsty during or after a workout? It is not uncommon to confuse the two sensations when it comes to your appetite and wonder, “Should I eat or drink, and when?” In this article, we will identify the body’s different signals and how to mindfully respond to them to manage hunger and thirst.

Hunger is the body’s signal indicating its need for food and energy. There are three types of hunger that reflect your body’s need for food in everyday life: physical, emotional, and situational hunger. First,  symptoms of physical hunger include stomach growling, weakness, headaches, loss of concentration, and mood swings. Be mindful of these physical signals and respond to them regularly because if they are ignored, then the body will release hormones that increase the sensation of hunger, decreasing the hormone that enhances satiety (Brown, 2017). Second, emotional hunger is the desire to eat to cope with feelings (i.e., sad, lonely, anxious, or bored). Unmanaged emotional hunger can lead to eating disorders and/or worsened emotional health, which in extreme cases professional support from a mental health counselor or dietitian is suggested.

The best way to manage hunger is to recognize these signals to distinguish between physical versus emotional hunger. Then, use The Hunger Scale to measure your hunger level before, during, and after eating to monitor your food intake:

1-Extremely hungry
2-Very hungry
3-Mildly hungry
4-Satisfied (not hungry nor full)
5-Midely full
6-Very full
7-Extremely full

Third, situational hunger is influenced by your surroundings. For example, extra-large restaurant servings, food ads, and your home and workplace influence your food intake. Furthermore, when individuals are eating and distracted by watching television, on a phone call, or browsing the web, their attention is drawn away from the food being eaten, which can lead to over-consumption (Crome, 2017). In response to these habits, the Food and Brand Lab recommends the “C.A.N.” approach, which encourages making healthy foods Convenient, Attractive, and Normal (Brown, 2017). For instance, consider decluttering your kitchen, pre-washing and slicing produce, preparing healthy meals in batches on the weekends for your workweek ahead, or replacing unhealthy snacks with better on-the-go options. As you can see, there are different types of hunger, but if you listen and respond to these signals mindfully, your relationship with food will be more positive.

Meal timing is key to workout performance and recovery. It is normal to feel hungry after a workout because exercise burns calories. Whether or not you eat before your workout can impact your hunger later in the day. In fact, exercising in a fasted state will lead to early fatigue, poor stamina, and increased hunger later (Bachus and Macdonald, 2015). Sheri Berger, BaySport Registered Dietitian, recommends that for quick energy, pre-workout meals should consist mostly of carbohydrates and consumed 1-2 hours prior to strength training (e.g., a smoothie or Greek yogurt with fruits, nuts, and honey) or having a small snack (e.g., granola bar, fresh fruit, or a bagel with peanut butter) about 30-60 minutes before cardio or circuit training. Following cardio or circuit training, eat a small snack within 30 minutes after your workout and a meal, composed of a ratio of 3:1 or 4:1 carbs and protein (e.g., pasta with a salad and a glass of milk), within 2 hours of finishing. Similarly, post-workout meals following weight training should be consumed within 2 hours and composed of a carb to protein ratio of 2:1 or 1:1 (e.g. grilled chicken with rice and broccoli). Whenever possible, choose whole foods.

At the same time, if you feel hungry, you might actually be thirsty. Thirst is the body’s signal that it is on the way to dehydration. The American Council on Exercise emphasizes that most people do not drink enough water before, during, and after exercise, but it is recommended to drink whether you are thirsty or not. Consider the various factors that influence intake throughout your day: sweat rate, water lost through excretion, food and beverage consumption, metabolic water loss and any water lost through respiration. Given that, the brain sometimes confuses a lack of fluid with not enough food, signaling physical hunger symptoms. In addition, be aware of concentrated and decreased urine (urine should be a pale yellow), weight loss, increased heart rate and low blood pressure, dry mouth and eyes, and constipation. Because water composes more than half of the human body, it is impossible to sustain life for more than a week without it and must be consumed to replace the amount lost each day during basic activities.

Water is the best form of hydration for most individuals, and it is recommended to drink eight 8 ounce cups of water a day. Before exercise, drink 2-3 cups of fluid 2 to 3 hours before workout and 1 cup of fluid 10 to 20 minutes right before activity. During exercise, drink 1 cup of fluid every 15 minutes, and after exercise, drink at least 2 cups. Sports drinks are not needed unless the activity exceeds 45-60 minutes to replenish salt lost during sweat. If sports drinks are unavailable drink water and having a salty snack (i.e. pretzels). Moreover, daily water intake does not always need to be met through the consumption of plain water (Nitschke, 2017). Foods and beverages possessing hydrating properties that work to our benefit include: fruits fresh, frozen or canned in natural juice, leafy greens, dairy, coffee/tea, tomatoes, and oatmeal.

In conclusion, listen to your body’s hunger signals and respond to them accordingly. Time your meals and check the hunger scale to monitor food intake, choosing whole foods whenever possible. Remember to drink throughout the day to quench your thirst and that there are alternative sources from which you can fulfill your daily water intake from. Taking steps to manage your thirst and hunger will promote a more positive relationship with food and a satiated appetite.

References

Bachus, T., R.D.N., & Macdonald, E., R.D.N. (2015, July 20). Why Am I Always Hungry After a Workout? Retrieved March 16, 2017, from https://www.acefitness.org/acefit/healthy-living-article/60/5552/why-am-i-always-hungry-after-a-workout/

Brown, K. (2017, March 10). All About Hunger. Retrieved March 16, 2017, from https://www.acefitness.org/blog/6331/all-about-hunger

Crome, G. (2017, March 7). Mindful Eating. Retrieved March 16, 2017, from https://www.acefitness.org/blog/6323/mindful-eating/?topicScope=nutrition

Healthy Hydration. (n.d.). Retrieved March 23, 2017, from

Nitschke, E. (2016, December 28). Eat Your Water – Sources of Hydrating Foods. Retrieved March 16, 2017, from https://www.acefitness.org/blog/6211/eat-your-water-sources-of-hydrating-foods

Author’s Bio

John Paul (JP) is a American Council on Exercise Certified Personal Trainer. He is a Bay Area native and long-time San Francisco Giants and 49ers fan. He spent most of the winter shredding the slopes on his snowboard, but is ready to hit the ground running again to train for his 7th full marathon.