I have some pointers for you that could help. For one, diet is so important, and I'd recommend that you consult a dietician about this. They can often be very helpful.
Also, doing isolation exercises on your core area will not burn fat much. Also, targeting an area (lile your abs) doesn't make the fat around that area go away. Your body uses its fat reserves over the general body. With that said, you will need to perform all round strenuous exercises to burn off fat. Cardio has some great efrects but what has been found is that weight lifting uses up more fat. But you also must co lnsider where your heart rate is at during exercise.
With weight lifing, your body requires larfe outputs of energy and can stimulate fat loss more readily than what cardio can.
Now, for dieting, know that quantity, quality as well as frequency are all important. What dueticians and personal trainers recommend is eating more frequently (6-8 times a day) instead of just 3 times. This helps increase the metabolism of your body (since you are loading it more, it steps up the rate a bit more). If you starve yourwelf, your body goes into a type of survival mode. So food will then start being absorbed as fat etc.
This is why it is so important to eat straight after you wake up in the morning. During sleep, you havent been eating for 7-8 hours. So your body needs to reload. If you dont in time, your body will take extra measures to make sure you can survive these starvation periods...store up more and more fat.
Now, the diet itself needs to be balanced. Protein, complex carbohydrates (no refined stuff), and healthy fats. Fats are important since most of your hormones require fat, and cell repair as well. Your cells are lined with lipids etc. Carbohydrates provide fuel fo your muscles etc.
Now, what you should watch out of is fruit intake. Fruit is incredibly fattening. My dieticians used fruit and fruit juice to help me pack on weight. Im off it now because I was developing a lot of stomach fat from it. But it helped at the start to fuel my gym sessions etc.
So stay far away from fruit. But obviously you need some fruit in your diet for the vitamins they provide. But generally, peolle have this perception that fruit isgood for your slim figure or something. Fruit is veeeery nutritious and healthy. But that is exactly why it's so fattening. Lots of energy!
Drink tea without sugar, drink milk without fat, and drink plain water. That is that. Nothing else. Sources of simple sugars really make people battle with lossing weight. I see chicks drinking flavoured water, fruit juice, and chowing fruit salads in tge hope that they will loose weight.