How can I make low cal diet healthier?

You usually can't. The goal of losing weight is keeping it off and improving health. Low calorie diets usually accomplish neither result. Instead, completely avoid foods that contain white sugar, white flour, white rice, and white pasta. Eat plenty of vegetables and beans and a fair share of fruits and nuts, and add wild fish like salmon and cod at least three times a week, stay physically active and watch lbs. Drop.