Sixteen
Sixteen Plus is an intermittent fasting tracking App. The idea is to record how long you went between eating (from your last food one day to breakfast the next day). You should try to keep a fairly small window in which you eat (e.g. 8 hours).
Plus
You might be able to enhance the approach by exercising within the fast time (the plus part). You can also track this by toggling the exercise icon.
NB
Please check with a medical professional before starting any kind of fasting diet and choosing a target fast time (if any). Im a Doctor, but of Economics not medicine, so you absolutely shouldnt take my advice on this kind of thing!