Sure, you may be a rational actor and come to your senses, but you are also poor, you have no vehicle, and you live in a food desert. So will you realistically be up for major modifications to your lifestyle and habits?

I hear what you're saying -- I think there are a few points here:

- Obesity is not isolated to food deserts. The people in food deserts may be in a pitiable situation, but most of us are obese; not just the people in food deserts. If obesity were isolated to food deserts, or even concentrated in food deserts, I might feel differently.

- Even the people in food deserts have access to nutrition labels. One thing that makes a lot of sense is ensuring you get your vitamins, and then keeping the rest of your food cheap. In other words, the most cost-effective food regarding calorie-per-dollar might be zebra cakes, but obviously you don't actually to just buy Zebra cakes. Living on black beans and rice might not sound appealing, but it is not the path to obesity. When you live on black beans and rice, other foods are your garnish. Sparing, small servings, but present from time to time. Most breakfast cereal is also effectively just grass seed + vitamin powder, as well.

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There was a time in my life where I had very little money, and I lived on black beans and rice for quite a while. I biked and walked around the city and I was thinner than I've ever been since.