If you are on your journey in losing weight or changing your physique for the better, you will need to stay strict and disciplined with the food and drink you consume. For too long you may have been used to eating whatever you want but in order to see a change for the first four weeks I recommend you avoid sugary and high in fat foods.
Imagine an alcoholic who has not had a drink for months and months and then is suddenly offered one and drinks it, what do you think will happen? All the hard work will be undone and all the old receptors will be reset because they will want to drink again. This is the same concept when you eat healthy for four or five days and then on the sixth day you eat whatever you want, your bodies receptors will then crave that food for a few days after ultimately undoing the hard work from the previous days.
Best thing you can do is eat well, stay healthy for four weeks and resist all temptation to bad foods. You will surprise yourself that when the four weeks are up and you can have something, chances are you won't fancy it because you won't want to destroy your progress :)