Crash diets are not considered a very good option for weight loss.But you can go for it if you want to shed some extra pounds urgently for any important occasion.In this diet you need to restrict yourself from any source of empty calories.Thus foods containing sugars,fats,starch should be completely avoided.You need to limit yourself to foods like boiled and steamed vegetables,clear soups,veg salads and fruits.You may also go for a liquid diet.Comprising of liquids like fresh fruit juices,lemon water,buttermilk,coconut water,clear soups and chicken broth.But not more than a day or two.These crash diets should not be continued more than a week.As these diets are deficient in many essential nutrients required by the body.Continuing these diets for more than 15 days,makes your body starved of many nutrients making it undernourished.