Bee, that may possibly be it.
Low carb food will keep you on track. But if you pick, pick, pick at it, then the portions increase beyond what you think you have eaten.
There was a programme on a while back. It put out nibbles for 2 groups of people to eat, I think it was chicken wings/drumsticks.
With one group, they filled up the plates, but left the bones/waste.
The other group, they filled up the plates, but took away the bones/waste.
The group that they took the bones/waste away from ate far more than the group that could see how much they had eaten.