Obesity, similar to high blood pressure and type 2 diabetes, is a chronic condition. If these conditions are left unmanaged they get worse and if treatment is stopped the problem comes back. This is why weight management strategies have to be something that you can do for the rest of your life. Short-term quick-fix solutions are not sustainable, which is why weight usually comes back on.
No single approach will work for every person. You will need a multi-component approach that addresses nutrition, physical activity and behavioural approaches with a long-term strategy to improve your overall health. It is important to talk to your GP about your weight and work with him/her when deciding which treatment is right for you.