Just the 'lifting 3 times a week' will take out a lot of the working population out of the picture. Why? If include commute to gym, working out time and shower/etc, we are looking at least 6 hours per week. Add the gym costs/going to the gym costs and you have maybe 100 bucks a month as a cost. We are fortunate we can spend that time/money on ourselves, but seriously, a lot of people can't. Heck, if you take 80% of the comments here in HN how they work 60+ hours a week in their startups, I doubt even us techies will have the time to do so.
In my country (and I think the USA as well) obesity is highly correlated with low income.
Then you have the psychological aspects to it. Stress is a major contribution to over eating. If everyday you are worried if you have enough at the end of the month for rent, you wont stop, go online, get a recipe, go to the grocery store to get fresh vegetables, come on, cook for an hour to have a nice healthy meal... You most likely will pick up a microwavable lasagna and be done with it.
I don't disagree with you that losing weight is easy, it is, basically "eat less than what you need", but being able to do that, based on many many factors isn't as easy.
(congrats on the weight loss)