Fitness Band Calorie Counter Accuracy Tests

Fitbit Flex Activity Data on App
Fitbit Flex Activity Data on App. Bruce Gifford/Moment Mobile/Getty Images

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 website.

Activity Monitors Tested for Calorie Accuracy

  • BodyMedia FIT: This now-discontinued 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 percent.
  • 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 percent 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. It was accurate to 10.4 percent for calories burned.
  • Jawbone UP: This now-discontinued 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 percent.
  • 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 percent.
  • DirectLife: This discontinued sensor was carried in a pocket or worn on a necklace. It was similar to the Weight Watcher ActiveLink, which uses the same technology. It was accurate to 12.8 percent.
  • Nike FuelBand: This fitness band was highly motivating but is now discontinued. It was accurate to 13 percent.
  • Basis B1 Band: This discontinued 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 percent. It was recalled in 2016.

Should You Trust Your Fitness Band Calorie Count?

Even the most-accurate activity monitor or pedometer had a 10 percent 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 chart.

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.

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 people make to justify what they 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. Fitbit and some other monitors have good integration of diet tracking with their apps and/or personal web dashboards.

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  1. Lee JM, Kim Y, Welk GJ. Validity of Consumer-Based Physical Activity Monitors. Medicine & Science in Sports & Exercise, September 2014 Volume 46 Issue 9 p 1840–1848. doi:10.1249/MSS.0000000000000287