But a study
https://www.theguardian.com/australia-news/2018/may/11/fitness-apps-found-to-make-almost-no-difference-to-users-health wrote:Fitness apps found to make almost no difference to users' health
Researchers studied a range of apps and found only one was effective, while others failed to spark improvements or made the problem worse
...
An app developed by the Swedish government to curb drinking among university students actually led to them drink more, while a globally popular fitness app made almost no difference to the weight of those who used it, a review of the effectiveness of health apps has found.
....
And it was found users of the popular fitness and diet tracking app, MyFitnessPal, showed no significant reduction in weight loss or behaviours around physical activity and diet when compared with those who did not use the app.
(Probably a bit unfair for me to highlight the MyFitnessPal mention in the article other than it is one I've heard of befor e(never used any of them myself).
Ian