Calorie counting / deficitsWatch
In long... not really and it can be complicated. So in order to be all round healthy for long term, it's important the we put the right amounts of each food group (carbs/protein/fat) into our body. You could live in a calorie deficit but all you eat is fat and sugars every day and this isn't great because you miss out on all of the goodness in other foods.
Also, you will find that if you are cutting down on calories but eating only foods in high calories but just in smaller portions then you're likely to feel really hungry! That's why foods like salads and fruits can help to fill you up so you don't get those food cravings without adding a lot of calories to your diet.