If you pay big bucks for a fitness band or app-linked activity monitor, is it counting your calories burned with any more accuracy than a $25 pedometer? Researchers at Iowa State University tested popular fitness bands and activity monitors to see if their calorie count matched up with a sensitive metabolic system monitor.
The researchers wanted to see how accurate they were not just for a workout bout, but during the variety of activities we do all day. They used 30 men and 30 women and a 69-minute period of 13 different activities. These included running on a treadmill, playing Wii tennis, working at a computer and playing basketball -- a range of light through vigorous activity.
All of the monitors tested track steps and calories, as do inexpensive pedometers. But most add other features and track data on an app or web site.
Activity Monitors Tested:
BodyMedia FIT: This armband activity monitor proved to be the most accurate. It uses several sensors besides the motion-detecting accelerometer, including skin temperature and heat flux. It tracks time spent in light, moderate, and vigorous activity and sleep. It was accurate to 9.3%
Fitbit Zip: The little brother of the Fitbit family, it can be worn on the waistband or carried as a pocket pedometer. It only measures motion, but was accurate to 10.1% for calories burned.
Fitbit One: The One also tracks stairs climbed and sleep quality. It is worn on the waistband or carried in your pocket. I've worn the One for years. It was accurate to 10.4% for calories burned.
Jawbone UP: This fitness band is worn on the wrist and tracks active time, idle time (with inactivity alerts), workouts and sleep. It was accurate to 12.2%
Actigraph: This sensor is often used by researchers, but is available to consumers. It can be worn on a wristband or a waist belt. It measures MET (metabolic equivalents), activity intensity, and sleep. It was accurate to 12.6%
DirectLife: This sensor is carried in a pocket or worn on a necklace. It is similar to the Weight Watcher ActiveLink, which uses the same technology. It was accurate to 12.8%
Nike FuelBand: This is the fitness band that made me a convert to wearing something on my wrist. It is highly motivating to reach your Nike Fuel goal for the day. It was accurate to 13%
- Basis B1 Band: This health tracker watch has sensors that detect heart rate, perspiration and skin temperature in addition to the accelerometer. It has excellent sleep-tracking and focuses on building good habits. But the researchers found it scored the worst for calorie tracking and was only accurate to 23.5%
I've worn and tested many of these same activity monitors side-by-side. While I'm only a sample of one, I found variations.
- I was disappointed that they didn't test the Fitbit Flex wristband monitor or the now-recalled Fitbit Force wristband, which are very popular. I found the Flex to match well with the Fitbit Zip and Fitbit One when I wore them at the same time.
- I found a similar variation with the Basis band compared to the Fitbit One and Polar Loop fitness band. The Basis usually gave me an extra 300-400 calories burned per day. That's a whole sandwich or an hour's worth of walking. The Loop's calorie count matched well with the Fitbit One.
Bottom Line: Should You Trust Your Fitness Band Calorie Count?
Even the most-accurate activity monitor or pedometer had a 10% margin of error. If you are aiming for pinpoint accuracy in matching up your calories burned vs. the calories you eat, remember to give yourself that margin. Match up what you see on your activity monitor with a calorie calculator such as our Walking Calorie Calculator.
If it's any comfort, the calories logged on an activity monitor are likely to be far more accurate than what you might see on the calorie display on a treadmill, exercise bike or elliptical machine. Those often don't account for body weight, which is a big factor in energy expenditure.
More: Can You Trust the Treadmill Calorie Count?
The researchers noted that people usually overestimate the calories they burn, so an activity monitor will at least provide an objective measurement. While it may not be completely accurate, it beats the guesstimates we make to justify what we eat.
Beyond tracking calories, several of these activity monitors have diet-tracking features so you can log your food intake and match it up with the calories you are burning all day. Tracking your diet accurately is probably even more critical for weight loss than tracking your calories burned. BodyMedia FIT, Fitbit, and Jawbone UP all have good integration of diet tracking with their apps and/or personal web dashboards. The Nike FuelBand doesn't integrate diet tracking, but it makes me move more than any other fitness monitor I've worn.
- Best Pedometers for Dieters
- Before You Buy a Pedometer
- 10 Ways to Motivate Yourself With a Pedometer
Lee, Jung-Min; Kim, Youngwon; Welk, Gregory J. "Validity of Consumer-Based Physical Activity Monitors." Medicine & Science in Sports & Exercise, POST ACCEPTANCE, 5 February 2014 doi: 10.1249/MSS.0000000000000287