The rule that I've been taught is - 3 meals a day, plus snacks (I go for 2 or 3 snacks on a good day).
I think you probably got some really good advice from your dietician and luckily they were able to point out where you were lacking or overdoing it. Good luck in working on what you discussed with your dietician

... I think it would help you to eat more often, remember to fit snacks in between meals, I think that keeps your metabolism working as it should and keep your energy levels where they should be. It's also a great way to fit fruit and veg in

(my current favourite snack is carrot sticks and hummus dip!)
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