You lost weight and now you're spewing judgmental advice. Am I now supposed to look at a fat person with scorn and immediately assume that they're lazy slobs? Should I suppress feelings of empathy? What is the actual point of what you're saying?
You spent 99% of your comment talking about your success and how you've gained insight into the unsatisfactory habits of others, and all of 1% acknowledging that it may be more complicated. And within that 1% you literally state that only 1% of fat people are losing to more than a simple mathematical equation. I know you coders like your elegant algorithms, but life is bit more messy than that.
Why wouldn't someone be empathetic towards smokers? They got hooked on an addictive substance at some point in their life and are now stuck with an unhealthy compulsion.
I think the unstated assumption OP is making is that fat people got hooked on food, and can't be responsible and give up their addiction. And while it may be hard to do, you only owe your inability to stick with quitting for your continued problems. Born again skinny people are particularly severe in this regard, since they've likely overcome their own personal issues with food (for now, at least) and so see that experience in everyone else. Maybe they made physiological excuses before, and tend to discount those issues in others; maybe their own feelings of weakness don't allow them to be especially empathetic.
And, the analogy to smoking is fatally flawed. Nobody needs cigarettes, but everyone has to eat.
Seriously, I'd like you to back that statement with some hard data. Not because I necessarily disbelieve you (lifestyle is a HUGE cause of weight problems), but because I think you underestimate how many people suffer from medical disorders.
A few illnesses that are characterized by an imbalance or an abnormality in your endocrine glands can also affect your weight. These include hypothyroidism (an underactive thyroid), polycystic ovarian syndrome, and certain unusual tumors of the pituitary gland, adrenal glands, or the pancreas. However, in the vast majority of people, these illnesses are not responsible for weight gain. Most are extremely rare. Hypothyroidism, which is the most common, is seldom the main reason for overweight or obesity. Treatment with thyroid hormone, while medically necessary, does not usually cause a significant weight reduction.
Genetic disorders
Obesity is also a symptom of some rare and complex disorders caused by genetic defects. These obesity syndromes usually appear in early childhood and are tied to several additional medical problems. One such disorder is Prader-Willi syndrome, a form of obesity associated with mild mental retardation that occurs in about 1 in 25,000 people and has been traced to abnormalities in a group of genes on chromosome 15. People with this disorder are unusually short and have primarily upper-body obesity. A less common disorder, Bardet-Biedl syndrome, is similar to Prader-Willi syndrome, but is caused by abnormalities in different genes. Several other rare genetic syndromes cause obesity, but account for only a tiny fraction of all weight disorders.
Geographically correlated obesity is explained by nutrition culture, not by geographically selective medical conditions.