There are some excellent responses here.
I don't think most people "choose" to become overweight. Obesity is a multi-faceted issue that involves our genes, environments, physical traits, emotional traits, and outright ignorance. I'm not trying to call anyone here "ignorant," but I'm sure many of us went through misguided attempts at dieting at some point simply because we didn't know better, or acted upon misinformation in attempts to eat right. I mean, most people still don't seem to realize weight is entirely dependent on calories in, calories out!
We live in an abundance of cheap, tasty, chemically processed, easy to access food. Some people may have genes that push them into powerful cravings of food that used to be scarce. Some may deal with anxieties that compel them to eat for reassurance. Some may not have that internal "switch" that tells them they're full. Some may have suffered through physical and/or emotional abuse and find comfort in food. Some may use their weight as a cloak of protection or invisibility. Some may not realize their current diet compels them to overeat. It's so extremely complex that the obvious answer (eat less, move more) is often not the easiest answer.
Those that struggle with their weight typically need to look beyond what they're eating to see
why. Understanding that
why is probably the most difficult aspect for most of us. As a kid I used to eat directly out of the sugar bowl by the spoonful. Is that normal? Probably not. I was still a grade-schooler when my mom taught me to hide the wrappers of whatever we were eating so the rest of the family wouldn't see, and I learned to hide things well because if she caught me binging on my own, I was in trouble. I used to horde and binge on Hostess pudding pies when I was in junior high, and kept a stash of canned frosting and plastic spoons hidden in the book shelf of my room long before I could even drive. How much choice does a child have in getting fat when their parents are teaching them to hide the evidence of a binge? When those habits stay with you as you grow older, it's easy to be blind to them, or even see them as "normal." And as you begin to realize it's not normal at all, it's even easier to beat yourself up over so feeling out of control with it like I did.
No one ever took me aside and told me I had issues with anxieties, all I ever heard was that I was a fat, overly-sensitive crybaby that lacked self-control. And since I was always known as the class crybaby that had absolutely no friends, I often turned to food. I became asthmatic and allergic to practically everything in sixth grade, and spent a lot of time in the hospital. When I was back in school again my lungs were so weak I wasn't even allowed to use the stairs, let alone participate in gym. It was a vicious, vicious cycle and I had no idea how to break it; all I knew was that I had become fat and "ugly," believing no one loved me because of it. I remember always feeling extremely, utterly exhausted and being told I was lazy when I couldn't keep up with everyone else. Not fitting in and hating myself made me eat even more.
So even if no one forced me to buy a package of cookies and down it in one sitting, I literally could not stop myself because I did not understand the emotional and even physical issues that drove me to eat the way I did.
I come from a big family on both sides. One of my aunts once fell out of bed; it took a team of 6 emergency response volunteers to get her back off the floor. The same aunt had a tumor in her neck the size of a baseball, but nobody knew since her neck was already so big. Most of my immediate family had issues with their weight as well, and I've lost both parents to cancer at much too young of an age (my mom when I was still a teenager, my dad only a few years later). My dad had severe issues with cholesterol (90% blockage in one of his arteries) and I'm pretty sure he believed he ate right (no fast food, not much junk) and he got exercise every day, but in the end he still ate more calories than he burned. But with neither of us really understanding calories, how was there any hope if he was already "eating right?"
Heh, I didn't mean to turn this into a big whiny rant, but I wanted to point out that it took me years and years to break the cycle. I turn 37 this week and I'm still fighting it. I had to learn what my trigger foods are and why I've always been prone to overeat. I've had to discover and acknowledge what my weaknesses are and that I'm basically a drug addict, just that my "drug" is processed sugar (and this is speaking as a former smoker and alcoholic). I've had to acknowledge that I was sexually molested throughout my childhood and that it was one of the earliest roots of my many issues. I've also had to battle with my anxieties and eventually discovered that a vitamin deficiency was basically causing my nervous system to short-circuit, and in the past the only way I had to even remotely calm myself was to eat. I felt completely helpless. I still do in weak moments. I'll always be a recovering fat chick, no matter how much weight I lose and keep off. I believe that for those of us that have had any issues with controlling food to the point of obesity (or beyond) will always have to manage it like the chronic illness it is. I mean, I can't eat certain foods in moderation outside of a controlled setting; it's not as if I chose sugar to be my drug, it just is.
So is it genetics? It's not that simple. Is it our environment? It's not that simple either. And it's definitely not as simple as eating less, moving more . . . even though that's the final answer we need. And in the end, I don't believe it's a "choice" by the normal definition. The true choices lie in gathering information, finding out what makes us tick, and thus learning to deal with the cards we've been dealt. Some can simply go on a diet and lose the weight, others have trouble sticking with diets (or healthier lifestyles, whatever you wanna call it) because they've yet to deal with their underlying issues.
I think calling it a "choice" is more or less a judgment upon others, simply because it comes off as an assumption over an issue that "shouldn't" be out of control, yet it often is because it's not something fully understood. Just my opinion though.