To lose 40kg in 1 year is possible.

Only one option - do both exercise and intermittent fasting.

1- exercise 5 hours a week. Do walking 5 times a week and an hour long walk each time.
2 -Only eat from 12pm to 8pm - which means skip breakfast and only have lunch and dinner.

If you do this for 52 weeks - you will sure reach 65kg.

Do you have a reason to cut weight so drastically?

Before you start - please seek doctor's advice on your health. You might have underlying issues that might prevent you to exercise and lose weight.