M indian.why sometimes two slightly obese girls of same height, weight, body shape have 2 different amount(one has more than the other) of belly fats?

Multiple reasons: Not everyone is the same in genetics, diet, exercise, stress, sleep patterns, etc. There are infinite varieties of combinations of factors leading to amount of belly fat. Diets high in sweets, processed foods, and other simple carbohydrates (like white rice) can lead to Insulin resistance and more belly fat. High stress and inconsistent sleep can also lead to more belly fat.