This topic is hardly a debate as it is well known that obesity has a massive negative impact on people's health. Those who are obese are suffering type 2 diabetes, heart problems, clogged arteries, the hardening of the arteries, lack of fitness, fatigue and many more major problems. If they are too obese they are at serious risk of very early death.
Obviously being fat obstructs one's ability to perform most physical activities, therefore making it almost impossible to lose weight naturally. It becomes more difficult the more overweight you are to complete simple tasks, such as walking up stairs. I'd say fat people have a "fat" chance at lessening the damage to their physical health due to their current lifestyle.
I consider myself big but not fat at 140kg and yes it does damage our physical health as it is harder to run around and be happy with your friends as most people would use the reason that your fat as a topic to insult you all the time. In saying this it means that not only does it affect your physical self it also hurts you mentally thinking you will never be able to lose that weight.