Protein and Fats vs Hunger???

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I've recently come back to MFP, now that I have finished with all my stress-related school work etc.

Before when I was trying to lose weight, I was aiming for around 2100 calories, and I was able to hit that, with a little bit of sacrifices. Now? I'm eating a lot of protein to be honest, a lot of protein and fat, and less than 50g of carbs a day, yet I'm hardly hungry? I am struggling to eat 1700 calories? I feel full, happy and full of energy, but does good sources of protein and fat really have such an affect on hunger?

Granted, when I first started, and largely for the entirety of my time, I had just kept to cals in vs cals out, and I ate a lot of simple/complex carbs, such as white bread, potato, vegetables, fruits and nuts, etc. But now I am only eating vegetables and fruit in the morning for my carbs, and eating large amounts of protein. (+1 for chicken and fish :D)