Unless prescribed by a doctor for a specific condition, we do not need diets. We need nutrition. We are often influenced by family and friends to try the latest fad diets because it works great for them. But, as discussed in the article linked below, not everyone enjoys the same results. Our body chemistry is unique to us. That is why it is difficult to declare a universal “best diet” that works for all.
Exercising specific body parts does not reduce fat stores in those areas. For example, more situps will not reduce belly fat. Proper nutrition—reducing all around calories—and full-body cardiovascular and resistance (weight-bearing) exercises to burn stored fat is the best general prescription for fat loss. However, spot training certain muscle groups can make them stronger and better toned. Read the discussion at this link for good exercises in the gynoid region (hips/thighs/buttocks).