There’s an app or smart device for every single activity of daily living now. Washing machines and dryers connect to smartphone apps. Refrigerators have Bluetooth-enabled speakers. Smart Home Assistants allow many to enjoy the experience of having a genius butler on hand all the time. The proliferation of apps and devices has naturally made its way into the world of health and fitness. Wearable technology allows athletes and health-conscious people to keep track of their vitals, and various apps promise to deliver the experience of a real live personal trainer for free or a small subscription fee. The question remains, though: do these apps and devices actually help people achieve their dreams?

A brand new app that’s getting quite a bit of press is called Fiit. Touted as the “Netflix of fitness,” Fiit offers an array of classes from kickboxing to low-intensity stretching to high-intensity impact training. In addition to the in-app videos that users are encouraged to “cast” onto TVs for the duration of the workout, the program also comes with a strap that goes across the chest of the user. This bit of wearable tech measures the user’s heart rate and breathing for a comprehensive workout report afterward.

Other apps encourage people to exercise by offering payouts for achieving certain fitness goals. Take for example Achievement, which offers a cash payout based on the number of “healthy activities” a user executes. With all these fun and engaging options, users of these apps and devices should be among the fittest people on the planet, right? Unfortunately, the proof just isn’t there — having these fitness apps or wearing a Fitbit does very little to help users lose weight.

A number of studies out of London, Singapore, and Pittsburgh have examined the habits and fitness patterns of subjects who wanted to lose weight and whether the fitness trackers helped them towards that goal. In the study out of Pittsburgh, two groups of adults were instructed to go on a low-calorie diet and exercise more. After six months, one of the groups was told to start keeping track of their diets and exercise regimens, while the other half was given a fitness tracker. After two years, the group with the Fitbits lost less weight, much to the researchers’ surprise.

What gives? A few important gaps in fitness tracker tech tend to stymie weight loss efforts. For one, the tracker only measures calories out, not calories in. Wearers who see that they’ve done extra exercise may reward themselves with extra food and in essence zero-out all the work they’ve done. Other problems include “rage quit” — that is, when a user isn’t getting results as quickly as they want, they become discouraged and abandon the effort altogether. Still more become bored with their new toy and do away with it if they’re not intently focused on their weight loss goals.  

Besides the scientific studies, other fitness app users find the apps intrusive. While the cost is lower than that of an in-person trainer, having a smartphone constantly on and taking up the user’s attention removes some of the joy of working out. For one writer at Men’s Health, part of the fun of going to the gym was disconnecting for a little while and zoning out to some music — an experience impossible if you’re following an app tutorial. In addition, a metastudy out of Bond University found that fitness app developers have little to no evidence backing up claims that they help users lose weight. Scientifically, any claim that the creators of these apps make amounts to a few testimonials and some marketing hype, but almost no hard evidence.

If you enjoy wearing a Fitbit or using a fitness app, by all means, continue to do so. However, remember that they aren’t a one-stop shop for getting the body you may want.