I'm switching from an unlimited data plan to a 4GB monthly data plan. For the most part this won't be an issue as I'll just use Wi-Fi when I'm at home, but I'm wondering about apps like Health and My Fitness Pal which constantly track steps/distance/calories etc. I have a feeling they use very little data as they just use the gyroscope/sensors within the phone and My Fitness Pal uses data from the Apple Health app. But does anyone have a definitive answer? How much cellular data would My Fitness Pal and Health use? I use My Fitness Pal a lot to log meals/calories/macros and use it combined with Health to track steps/distance/calories. I guess the only real data it uses is to uses the internet to find food items that are logged already by someone else and I can't imagine it uses very much to do that.