Q: How do I get in shape for my summer holiday
A: Don't eat so much, fatty!
Simple, right? No, that's why everything has to be dressed up as 'six pack shortcuts', 'beach lean in fifteen' and so on. People want the easy route which isn't going to impact their lifestyle too much. So it's a question about how much you want it over how much do you want that burrito with all the extras for lunch today.
It doesn't matter how you achieve it reducing calories in means that your body will have to find other sources of energy, such as easily broken down carbohydrates (stuff you've just eaten) once that's all gone then your body will turn to other sources of carbs in your muscles (glycogen) then move onto your fat stores (triacylglycerols present in adipose tissue).
Only once fat stores are low does your body turn to breaking down protein (your muscles!) for energy as your body needs to keep as much lean body mass as possible. It takes around 24 hours (person dependent, natch) for you body to have used up all your glycogen stores
So if you want to burn some fat and know you're burning fat then some fasting is in order, that's right starve yourself, don't eat any food (or severely restrict your calorie intake to under 500 calories) for 24 hours. The net result of this either one or two days of fasting a week is that your total calories for the week/month/year come down.
The only thing with this sort of diet is there's nothing to sell, nothing to consume so the fitness industry has nothing to sell you and make money off of you.
This approach has served me well for a good 4-5 years now, I have had lapses and piled the weight back on after having a cheat day/week/month but am trying to get back on track with this tried and tested formula which is basically "don't eat so much fatty!"