I really rate myfitnesspal and have been using it for a few years getting me down from 16 to 14 stone.
However, I'd urge a word of caution around the calorific values it gives to exercise. In my case MFP reads very high. For example, this weekend's parkrun according to MFP should have been 467 calories, yet my Garmin 620 gives me 417.
Differences are much greater, the further I ran. Eg, a 6 mile tempo run according to MFP was 928, but the Garmin gives 791.
So, whilst I know even the Garmin isn't wholly accurate, it's probably better to rely on that than MFP.
I also note, my 620 gives lower calorie readings than my 305 used to as well.