Usually, low calorie diets are no carbohydrate diets. We need carbohydrates, however, there are good choices and there are poor choices when it comes to carbohydrates. Consuming high glycemic foods will cause your insulin levels to elevate. High insulin leads to MORE fat storage. Yes, insulin is a fat storing hormone. The purpose of insulin is to keep blood sugar levels in a specific range. Which means that insulin allows sugars to enter the cells and therefore, decrease blood sugar when we eat. When we consume foods high on the glycemic index (higher in sugars) insulin is produced in greater amounts, not only will this cause us to store these foods as fat in fat (adipocytes) cells, but it will cause blood sugar to drop and therefore create an increase in appetite. One of the problems with low calorie diets, is that people often choose to eat pre-packaged junk food. Why? Ease and clever marketing of 100 calorie packages. The problem is it is deficient in actual nutrients and high in sugars that will cause the increase in insulin - increase in fat storage - drop in blood sugar - increase in appetite cycle.
The other reason you don't lose fat on low calorie diets is because it costs the body less energy to burn a pound of muscle than it does to burn a pound of fat. Your body is very thrifty and chooses to conserve energy. Therefore, if it only takes 580 calories (energy) to burn a pound of muscle and 3500 calories (energy) to burn a pound of fat, which do you think it will choose? Muscle. That's right, it will actually break down lean tissue before fat tissue. Also, your body thinks you are going into starvation with the low calorie diet, so it begins to store up energy. Building fat tissue is how the body stores energy. In reality, the low calorie diet is setting you up for failure. You think you have lost 5 pounds of fat, but you have actually lost more muscle and gained more fat. That is why when you begin to eat in your "old" ways, you gain that weight back plus 5 pounds. You never really lost them to begin with.
There are many ways to go about fat loss, but every body is a little different. You need protein, carbohydrates and fats with every meal. Choose complex carbohydrates, in other words vegetables. Many people will eat more fruit on low calorie diets, but many fruits are high on the glycemic index and therefore, should be eaten in limited amounts.
Also, build that muscle! Weight training, yoga and pilates are great ways to build muscle and therefore use muscle and fat in their appropriate methods of use. You do not need to go crazy lifting weights for hours every single day. There are many great body exercises you can do at home without weights. You can get a fantastic full body weight and cardio workout by simply doing body exercises, like burpees, planks, push ups, bear crawls, mountain climbers and so much more.
So, stop starving yourself. There are better, more effective ways to drop those fat stores. And, be gentle with yourself. You did not gain 30 pounds overnight and you won't lose it overnight either.