I recommend tracking your daily food and drink consumption eg use MyFitnessPal which is free and very simple.
Cutting out sugar will help a lot - replace with vegetables not fruit.
No alcohol and avoid fruit juices.
Set yourself a target that you won’t eat anything and will only drink water between 8.30pm and 8am next day.
After two weeks the cravings and hunger pangs will start to subside and you won’t feel inclined to raid cupboards. Get yourself an Advent Calendar and open the windows each day to help you count down - if you can keep your healthy habits for 24 days it will be a lot easier to keep going after that.
You have to treat it like a challenge - imagine your life truly depends on it. If your diet already seems healthy then look at how much processed food you are eating as often there is hidden sugar in these foods.
Look for foods that have low GI and can help you regulate your blood sugars - chia, garlic, legumes like chick peas and whole grains, boiled potatoes not mash, almonds, apples,blackberries, edamame, olives, Greek yoghurt ,air popped popcorn!
It doesn’t have to be a boring diet.