You can eat real food instead of processed garbage, for starters. Nobody's getting fat eating vegetables.
You end up with the cheapest calories being lightly processed grains like rice and flour, then you end up with more processed grains like white bread and ramen, then move to things like peanut butter, before hitting junk food. The point is that the cheapest calories aren’t exactly healthy.
The produce aisle tends to be pretty expensive per calorie, potatoes excepted, since veggies aren’t calorically dense, and are sold mostly by weight.
I challenge you to find any junk food that comes even close to that kind of caloric density per dollar. The cheapest junk food has a tenth of the calories per dollar than a bag of rice from Costco (4-5k calories per dollar), at best.
The problem is that the cheap stuff takes a little effort to make tasty compared to the hyper-palatable junk food. The whole "junk food is cheaper than whole foods per calorie" is nonsense.
The point is, if money is tight, which invariably means that time is tight, people don't have time to cook dried pinto beans, or make bread for EVERY meal where the prep time is roughly 12 hours. Add into that, even knowing how to cook is a skill. An all bread and pinto diet is likely to take more time than most people have, and not yield a great health outcome anyway.
If you look at it as categories, the junk food, and processed food aisles are where you are going to on average get your dollar to go furthest.
The whole point of the "myth" is that it is FAR more efficient and cheaper to get everyone enough calories with food from the junk aisle. The origins I believe come from a cooking show where the budget and time were limited. Professional chefs gave up.
Here's the challenge: you need to serve a meal to 4 people (2,500 caloriesp) you have $10 and 1 hour including shopping and cooking. I can think of half a dozen meals that come from processed foods where that is possible, but doing that with fresh foods is HARD.
If you want to go the pure science route, here's a peer review study from the NIH showing that in many places on earth, healthy food is provably more expensive https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6825829/
See: potatoes. They're basically pure calories and they're several times cheaper than any junk food. Junk food is the most expensive food no matter how you slice it. The only metric by which junk food might win is in the lazy glutton category; if somebody is too lazy to put a potato in their oven 45 minutes before their meal, then a bag of potato chips has an advantage. But in no other sense is junk food more efficient. And even for lazy people, there are plenty of cheap as dirt veggies that require less cooking or no cooking at all. A bag of apples is a very cheap way of getting a sugar rush without any food prep, but fat people would rather spend that money on several gallons of cola a week.
No one ever got fat eating only vegetables. But you can't eat only vegetables and get all the necessary nutrients(at least not easily).
Eat healthy food, and eat only when you're hungry, and most likely your body would auto-regulate the calory intake just fine.
But I also managed to lose 30kg eating (lean) meat, full-fat dairy and almost no green vegetables, just a lot of oats for starch/fibre and nuts for extra protein/vitamins/minerals and healthy fats.
But it's also just really hard to tell what food is actually healthy. Some foods are obviously healthy. Some are obviously unhealthy. But a lot is in the middle somewhere, having both healthy and unhealthy aspects.
Some foods are even controversial in the research, like butterfat which many people lump into the group "saturated fats", which is universally thought to be unhealthy by laypeople. But there are multiple types of saturated fat(ty acids), so it's actually really complicated.
My rough intuition based on reading a bunch of research is that dairy fat is actually quite healthy in small amounts(it's very calorically dense). I could go into a lot more detail on why but the gist is butterfat has a lot of short- and medium-chain fatty acids, which are good. It's the long and very-long you want to avoid.
The 3-4 meals + the constant availability of food is definitely new.
The human brain's ability to use ketones(byproducts of fat metabolism) for energy is actually unique to humans, suggesting a selective pressure towards surviving starvation in our evolutionary past.
You aren’t marching in a legion, working in the fields or building a giant monument without proper food.
Since food preparation took much more time and the logistics were complicated the number of meals and choices were limited but pretty much every meal was packed with carbs and often with fat too (lard, oils etc).
Sweeteners whether it’s honey or other sugars were also quite common and very much so not limited to the ruling classes.
our brains use a very large share of our total energy; so that adaptation may just be a requirement of additional brain energy use and not a adaptation particularly for starvation levels higher than other animals.
It's important to point out that for a lot obese people, hunger hormones are going to be out of whack. So while following hunger might certainly be good for avoiding obesity, it's not necessarily as helpful in losing weight.
However, you don't have to be that "extreme". Just eating mostly vegetables and cutting out all the obvious crap will do.
The fact that this is somehow unimaginably strict to many people just shows how completely fucked up our relationship with food is. Most of the foods that make us fat didn't even exist a hundred years ago (at least in its modern, highly processed form) and now people somehow can't imagine living without them.
Getting iron from non-heme sources is also kind of hit-or-miss.
Throw some eggs or lean chicken meat into the mix and you've got a complete diet that would be very difficult to become fat on.
High-starch vegetables are a major contributor to obesity.
I bet that it is the "frying" part or the sauce or butter that comes with it, that leaves a lasting impression on the hips.