Obesity is a complex disease. I have come to appreciate this even more over the last 5 years, and what I am about to say in this post is NOT a refutation of that complexity. Instead, I want to make a point that though obesity [whether becoming obese in the first place or remaining obese after an effort to lose weight] is an intricate mess of bad decisions, bad environment, genes, social pressure, family customs (not traditions, but the every day way of preparing foods or eating that we learn from our families), lack of physical activity, metabolism, gut microbes, infections, injury and things we haven't even discovered yet - even though this is true, on its own, what we eat still matters.
Yesterday, I was waiting for my train to arrive at 30th St Station in Philadelphia PA. I had been traveling over the weekend. I had an hour wait and was standing - standing - at a table, eating a salad that I had prepared and carried with me. I am a small person, slight of build, low weight. I am this way purposefully, not genetically; I share the same food environment, social pressures, and family cooking practices as most of you - some of whom are normal weight, and if the CDC is to be trusted, most of whom are not. As I ate my salad (which I found delicious with its ample amount of lean protein), I looked across the room and saw a person who was not slight of build and they were also eating. Eating from a box. A box of dunkin donuts. This is not a judgement, several of the things I listed in the first paragraph factor into the decision for that person to buy donuts. My point is, the food we eat still matters and even if it is not that simple in the grand scheme, it certainly is at some level. The small person was eating the salad. Maybe the small person routinely eats low calorie foods and doesn't exceed the calorie requirements to maintain a normal weight - and the large person routinely eats calorically dense foods and does exceed the amount they need.
NB: I didn't post this right away, its been a week since I was at the train station. So I have another observation to add. I was at dinner with friends the other night where I ordered a beautiful steamed seafood and vegetable entree. The man to my left, who is somewhat overweight (we had to trade seats at the movies recently because he was too large to sit comfortably unless in the aisle seat) was the first to request and be disappointed that the restaurant did not serve dessert. Not a judgment, an observation.