> Another example is obesity. Many people still chalk this up to a "moral issue" where people are making "poor choices", but that doesn't seem like a good explanation for why we live in an obesity epidemic.

I'm going to add to the noise and give a "simple" answer: Prosperity and availability.

Years ago I read an interview with an applied mathematician who did a lot of research on how food impacts the body - from a math perspective. He said that many things impact a person (and society's) weight. You've got the type of diet (carbs/proteins/fat/fiber). You've got the components of the food (stuff in nutrition labels). You've got genetic factors. You've got parasites. Health issues like hypothyroidism. And more.

But they don't impact you equally. When looking at the contributions of each factor to the rise of obesity, one item stood out clearly:

The production (or rather, overproduction) of food. It's really that simple. As the decades go on, we produce more food per capita than in the past. Some of it, of course, is wasted. But otherwise, the food has to go somewhere. And that somewhere is us.

From what I've read, in the 1960's, the average plate size was 75% of what it is today. Most people don't measure the amount of food they put in a plate. They eyeball how "full" the plate appears. Increase the plate size, and you increase your food consumption. When I switched to smaller plates, I still feel satiated - I'm likely still overeating.

In the US, finding smaller plates (that are not flat, and not bowls) is not easy. I had to resort to visiting Chinese/Korean/Japanese stores to buy them. Presumably they still use smaller plates in those countries.

How often do you feel hungry? Not craving hungry but stomach pangs hungry? I was very thin when young and was known to eat little. Hunger pangs were part of daily life (and not a sign of malnourishment). You eat breakfast, and you should get hungry by the time you eat lunch, and so on.

I now go months before I feel any such thing. I often skip lunch altogether. Part of it is due to slowing metabolism, for sure. But the reality is I'm eating quite a bit for breakfast and random snacks.

I grew up in other countries. Portion sizes at restaurants in the US are huge. For a long time I avoided eating at such places because it was just too much food. I often would have enough leftovers for another meal. People who consume a whole entree are likely eating way too much.

And that problem exists everywhere. In other countries, the standard Pepsi can was 330ml, and you could easily buy 220ml ones. In the US, it's gotten hard for me to find a chilled 350ml can when I'm on the go. Regular grocery stores don't carry them. Now most gas stations/convenience stores don't either. You get 500ml bottles/cans. Ever read the nutrition label on them? 500ml bottles are listed as 2.5 servings. People consuming them are consuming a lot.

I've mostly switched to the 220ml cans for soda. It's extremely rare that I drink one and think to myself "That really wasn't enough. I need to drink more!"

Tic Tac boxes are larger in the US than in many other countries.

The nearby Target only has "supersize" chocolates at the checkout register. You want a smaller portion size? You need to buy a whole box.

I won't even get into cookies. They're huge in the US.

Milk shake type drinks are both huge and loaded. In many countries, the portion size is small (e.g. 250ml), and they have the good sense not to put ice cream in it!

Desserts, in general, are crazily loaded. Any dessert that's over 350 calories is too much. Dessert is supposed to be a "sweet extra", not a whole meal. I'm looking at a popular chain's milkshake calories. The lowest is 680. The highest is 1160.

Often, when you get a dessert item from a restaurant, you are consuming the calories of 1-2 meals just from the dessert alone.

I won't even talk about cheesecakes!

Sorry, I know it's distracting from your overall point. Of course, environment matters. If you happen to have a lot of junk food at home, it's hard not to eat it. If you go to stores that have your favorite snack by the counter, it's hard not to buy. These do play a role. But as the researcher said, it's secondary/tertiary.

But to anyone trying to figure out why it's so hard to lose weight:

1. Get smaller plates.

2. Try to reduce food intake so you feel hungry at least once per day (I achieve this for a while, and then drop the ball). Don't feel bad if for a long time you're having only 2 (or even 1) meal per day. It'll take a while before your body will feel hungry.

3. Drink soda in the smallest 220-250ml cans/bottles. Prefer Izze over Pepsi/Coke. And prefer Spindrift over all (it's OK that Spindrift is over 300ml!)

4. Avoid foods that trigger cravings. The usual offenders are fried/salty foods. If you get soda cravings, track whether you just ate some fried/salty food. If you want an extreme experiment, try eating really bland foods. You'll notice you probably never get a soda craving.