For me, it is 100% my fault. It isn't societies fault, not my parents, not my ancestors....being fat was all me.
From my standpoint (and I am only referencing my life, in which I have had no medical issues resulting in weight gain, mental confusing to fullness, etc etc), obesity was absolutely my fault. I wasn't quite obese, but certainly overweight, so I will still chime in.
I don't think genetics, family history, or anything like that plays a role in being so heavy. My dad's side of the family is large. Just about every single aunt and uncle I have, plus most of my cousins, are overweight. I think it is because my family gatherings revolve around food and alcohol, so that is how those individuals approach their day to day life. It was how I approached mine. Food was to be delicious and consumed, as much as you liked. Alcohol was to be enjoyed, sometimes a little too much. But even if those were my surroundings, I still knew it was more than I needed....I just did it anyways.
Once I stopped eating so much, drinking so much, and started working out, I lost weight. It was as simple as that (although it was hard work to change my habits!). I still have some pudge. While I believe THAT could be due to the genetics on my dad's side (I have this whole theory on how where your ancestors are from determines if/how your body holds onto some fat; in a nutshell, if you are from a cold environment, it holds onto a little more for warmth; a warm environment, your body wants to get rid of it for easier survival in warm temps), I know that being overweight is never a necessity for survival so I cannot blame my genetics on that. So my main point is that I am nowhere NEAR overweight anymore. Maybe my body isn't perfectly toned and tight, but being fat was entirely me. It was my choices, it was my excuses, it was my eating habits.
7/1/13 My Goal: to be 150lbs! for every mini goal met
Mini goal 1: 160 (my lowest consistent weight)
Mini goal 2: 156 (my lowest adult weight EVER)
Mini goal 3: to SEE 150 (New territory!!)
GOAL: To have a fluctuation be UNDER 150