body weight should be in regards to your height.
therefore calculating BMI is a great and simplest way to know whether you are over weight or under weight.
if your BMI comes between 18.5 to 25, your body weight is normal. no need to increase or decrease.
if its more than 25 only then you need to be worried about decreasing your weight.
some tips that can help are
1. drink lots of water
2. divide your meals into 5 smaller ones
3. high protein diet
4. green tea, green leafy vegetables and fruits
5. low carbs.
along with your exercise.