However much weight you want to lose, you should set realistic targets - do not try to lose too much or you will either fail, or succeed in the short-term and then put it all back on again.
You can, of course, set long-term targets for example the weight or the Body Mass Index (BMI) that you want to be in two or three years time, and plan how you will get there. You may want to tie your long-term target to a big event - a special birthday or anniversary. Then set some short-term targets to help you on the way to your long-term ones.
It is not easy to lose weight and keep it off, it will take effort, but with proper planning and commitment it can be done. If you have tried to lose weight before and failed, or succeeded and then put it back on again, if is even more important that you plan carefully.
If you are overweight or obese, to be realistic and stand a good chance of succeeding, you should aim to lose 10% of your current weight. The calculator below can work out how much this is, for you. Research has shown that aiming for smaller weight losses helps people lose weight permanently.
Most overweight or obese people want to lose more than 10% of their current weight, if this is true for you, Weight Concern recommends that you lose 10% then try and maintain your weight at its new level for a few months, before attempting to lose another 10%. You will eventually lose all the weight you want to, and will have learnt how to avoid putting it all back on again.
If you think that 10% is too much to try and lose, do not give up - try to lose 5%. With a loss of just 5%, there will be improvements in your health and you will feel better. Having succeeded once, if you maintain your new weight for a few months you can then try and lose another 5%.
less than 18.5: you may be underweight
from 18.5 to 24.9: you are at a good weight
from 25 to 29.9: you are overweight
30 or higher: you are obese
Link: How can I lose weight?