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January 15, 2016
Activity Trackers Can Benefit Lifestyle Changes

NIDDK’s Dr. Kong Chen says activity trackers are useful, but only when used appropriately.
NIDDK’s Dr. Kong Chen says activity trackers are useful, but only when used appropriately.

PHOTOS: ERIC BOCK

An activity tracker can be a valuable tool to motivate a person to lead a more active lifestyle if it’s used to measure progress over time. That’s the advice Dr. Kong Chen has for people who received a device over the holidays or bought one to follow through on a New Year’s resolution.

These wireless devices provide information about a person’s habitual activity levels and exercise patterns. Depending on the type and model, an activity tracker can monitor heart rate; count steps, stairs climbed and calories burned; and provide a snapshot of sleep quality. And they can beworn on the wrist, upper arm, ankle or waist.

“The ultimate goal of an activity tracker is to help you achieve and maintain an active lifestyle,” said Chen, director of the human energy and body weight regulation core and acting chief of the energy metabolism section in the Diabetes, Endocrinology and Obesity Branch at NIDDK. “I would not recommend using an activity tracker’s calorie estimation to plan a diet.”

He said most people who buy fitness trackers are probably trying to lose weight.

Activity trackers contain a device called an accelerometer, which detects when a person is active, sedentary or asleep, based on movement. He said an algorithm uses the movement data to estimate calories burned based on a person’s gender, age, height and weight. Often, a tracker connects to a smartphone, computer or tablet, where users can view summaries of their daily activity and even set goals or challenge their friends on social networks.

Chen models a variety of activity trackers, which can be worn on the wrist, upper arm, ankle or waist.
Chen models a variety of activity trackers, which can be worn on the wrist, upper arm, ankle or waist.

Because activity trackers use proprietary algorithms to estimate calories, walking/running distances and sleep quality, it’s difficult to determine how accurate or precise their data is without good validations by research studies, Chen cautioned. Because of this, a user should not rely exclusively on the data.

“If a tracker says a person burned 1,000 calories during exercise, he or she shouldn’t eat an additional 1,000 calories,” Chen said. That could lead to unanticipated weight gain due to the potential inaccuracies.

Planning a diet and fitness regime based on one fitness tracker’s data is like investing money based on one stock market index, he added. There are several indexes—each one measuring one part of the stock market. While an index can provide important information about a sector of the economy, an investor shouldn’t rely solely on it to make financial decisions. Trackers have similar limitations.

Most consumer activity trackers are, however, “sensitive enough to measure a change in physical activity levels.” In other words, the devices allow users to monitor their progress over time. If, for instance, a person sets a goal to walk more, he or she can use the tracker to measure progress.

Chen compared activity trackers to personal trainers. Both provide motivation and individualized attention. Neither alone can get someone in shape. A person must be committed to losing weight. He admitted that losing weight is not easy because it’s “an uphill battle” that doesn’t happen overnight.

It takes a lot more than working out to shed excess weight, Chen warned. Besides exercising, people should carefully look at their diet. Losing weight is a complex process influenced by many factors, including a person’s age, body composition, family history, other health conditions and lifestyle.

For those considering buying an activity tracker, Chen advises thinking about how they want to use it. If counting steps is a goal, a pedometer will do fine. If someone swims a lot, he or she should select a waterproof tracker. Chen also suggested that people talk to their friends about what kind of devices they use. The user should view the activity tracker as a tool to achieve his or her goals and not the sole means to lose weight.

“Any device will do as long as you use it correctly and effectively,” he said. “However, no device will lose weight for you. It will help you plan, but you’ve got to follow through.”


NIH Body Weight Planner Helps Users Set Weight Goals

For those who would like to lose weight, but don’t know where to start, the NIH Body Weight Planner might be a good place to begin.

Body Weight Planner screenshot

Developed by NIDDK’s Dr. Kevin Hall, the Body Weight Planner forecasts how body weight changes after people alter their diet and exercise habits. It takes into account what happens when people of varying weights and diet and exercise habits try to reduce their weight.

The planner asks for a person’s height, weight and age. It also asks for his or her current physical activity level, what the goal weight is and the time frame for reaching the goal. Then, the planner calculates how many calories a person must eat to maintain current weight and reach and maintain the goal weight.

For information, see https://www.supertracker.usda.gov/bwp/index.html.

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