Diet and exercise. You can loose much more weight by adopting a healthy diet of lean protein, fruits and veg, whole grains and healthy fats (in moderation), than anything else. However exercise is an important part of a healthy lifestyle, and not only wil help weight loss, but improve many other health aspects. Make sure you don't do too much too soon, and consult a doctor before you start anything new.
Eat less. You are made of fat, muscle & water. When overweight, we want to lose only fat, not muscle which is what most people lose when starting a weight loss program. So eat 500cal/day, drink alot of water, eat lots of fruits/veggies, lean proteins, whole grains. Avoid alcohol, refined & processed foods and sugary drinks. Exercise 150min/week to help with weight loss.