Will an Apple Watch or Fitbit make you lose weight? Don’t count on it.

When I wore my first Apple Watch in 2015, I was smitten with the idea that quantifying my activity might empower me to get moving and lose weight like my doctor ordered.

After now tracking 25 million steps, my weight is about the same. Did closing all those rings actually do anything?

Researchers have been asking the same question for nearly a decade now. What they tell me: Buying a fitness tracker or smartwatch isn’t going to help you lose weight. In fact - yikes - wearing a gadget could even undermine your efforts.

Exercise is very good for you, and if your tracker helps you keep moving, then by all means keep wearing it. But like so many other wellness products, trackers have been marketed more with hype than with evidence.

What the research says

Research moves slowly in academia, but one of the most notable studies of the health outcomes of fitness trackers was published in 2016 out of Singapore. It found that people who wore a Fitbit kept up their physical activity a bit better than a control group without them — but after a year, it wasn’t enough to produce changes in weight or blood pressure.

The central premise of trackers is that “if you give people information, they’ll do something to change their behavior,” says John Jakicic of the University of Kansas Medical Center, who studies obesity and weight regulation. But that’s not what happens after the initial fascination wears off, he says.

“When we’ve given devices to people, it generally doesn’t change their behavior,” he says. “And if it does, it changes it for a very short period of time - maybe about 2 to 3 months, maybe a little longer - before the thing on your wrist finds its way into a drawer or you simply stop paying attention to it.”

Jakicic helped conduct one of the largest controlled studies of tracker tech, published in 2016 out of the University of Pittsburgh. It found that dieting adults who wore a generic activity monitor for 18 months lost less — yes, less — weight than those who did not. The people who wore the devices also generally moved less.

One theory: Just the act of measuring your body could change the psychological experience of being active. A 2016 study by Jordan Etkin of Duke University found that measurement can undermine the “intrinsic motivation” of activities like going for a walk, and make it feel more like work and decrease continued engagement in the activity. “They can’t give you motivation,” Etkin says.

We still don’t understand how they impact people in different ways. Some people with trackers get energized by competing with friends and family members to move the most. But for others, seeing their watch report that they have had a lazy day can contribute to self-sabotage. A 2017 study of adolescents found that trackers negatively added to peer pressure and were demoralizing.

I saw the Apple Watch’s possibilities - and shortcomings - when I came back from parental leave last year. A few weeks into resuming work, which involves long stretches at a computer, Apple’s Health app popped up a warning: My steps and standing hours had fallen off a cliff. I joked that my Apple Watch thought my job was killing me.

It was a useful heads-up. But what was I supposed to do about it? My Watch had no insight even on what my new goals should be. Eventually, I learned from other parents the joy of the after-work stroll with the kiddo.

What the tracker makers say

Apple told me it does not track research about weight loss because that is not the focus of the Apple Watch. (That’s disappointing.) But Apple did point me to a 2018 study by the RAND Corporation of programs that give people rewards for meeting certain goals with their watches. Those people had a 34 percent average increase of tracked activity days per month, and that persisted after the end of the program.

Fitbit, owned by Google, said its devices are useful for a holistic view of your health, including weight management. It pointed me to a 2020 analysis of 37 controlled trials that found using Fitbits during interventions has been associated with both weight loss and increases in step count and moderate-to-vigorous activity.

But in the majority of those trials, the people wearing Fitbits were also given other content and support.

The gadgets alone “don’t provide that additional support needed for long-term, sustained behavior change - things like social support or goal setting, demonstration of behaviors by other people that are like you and action planning,” Matt Buman of Arizona State University says.

How WeightWatchers uses trackers

If anyone had figured out how to make use of activity trackers, I figured it might be WeightWatchers, also known as WW. Today, roughly 40 percent of its members use trackers to automatically enter exercise data for its programs, chief scientific officer Gary Foster says.

Yet the company hasn’t linked their use to better weight-loss outcomes, in part because people don’t use them consistently. What it can say, Foster told me, is that wearing a tracker makes the work of staying on top of your exercise easier.

But a fitness gadget still can’t automate what Foster considers most important data in weight loss: what you eat. Foster says he does get calls about once per quarter from people with a new idea for a gadget to measure eating, such as sensors on teeth, but “it’s not there yet.”

Bottom line, Foster says: “Tracking your activity is going to have little or no effect without this surround-sound support of what to do with that information.”

One tiny win

If the controversy about TikTok’s Chinese ownership leaves you feeling uneasy, you can help protect yourself by giving it less data about yourself. A good place to start: not sharing your contacts.

Tap Settings, Privacy, Sync Contacts and Facebook Friends, then make sure both are switched off.