Every year I go backpacking out in California/Washington/Oregon, usually for around 2 weeks at a time. I set out with all my gear and about 5-6 days worth of food at a time, and plan my resupply points ahead of time. I do about 15-20 miles a day, at elevation, with 25+ pounds of gear, water, and food on my back.
The food that I pack is not healthy, and it's really kind of impossible to pack healthy foods. You can't really pack fruits or vegetables out there, nor would you want to. You need to calories and energy. As a result, the foods that I consume are pretty much pure junk. CLIF bars, candy bars, Pop Tarts, dehydrated rice dinners, candied almonds and nuts, etc. Really just processed junk. But, it's got a lot of calories and doesn't spoil, so it's pretty much all you can pack when you go out there for days on end. I usually pack around 3,000 calories worth of food per day, and I definitely need it. There are times where even after eating all my food, I still get into my sleeping bag at night and am hungry.
Here's the thing though - after my trips, I always lose weight. And not just one or two pounds. I'm talking 7-10 pounds over the ~2.5 weeks that I am out there. Despite eating 3,000 calories worth of pure junk per day, I'm still losing insane amounts of weight.
Over the years, I've had other friends and family join me on these expeditions. My dad, brother, friends, and cousins have all come with me at one point or another. And despite our differing BMIs and weights, the same thing happens to every single person - they all lose significant amounts of weight. Despite the fact that we're all eating thousands of calories worth of junk per day, everyone drops a ton of pounds. Because we're burning significantly more than we're bringing in each day.
And it all comes back to what we've heard time and time again - calories in, calories out. It's that simple. Obviously, going out and hiking in the mountains all day for 2.5 weeks isn't something someone can just randomly go out and do if they want to lose weight. But it does reinforce the importance of calorie management. Eating clean, healthy foods while cutting calories and exercise is the key to all of this.
The first line of treatment for chronic diseases like Type 2 diabetes, heart disease, etc, isn't medication or surgery. It's lifestyle changes. Almost half of all newly diagnosed type 2 diabetics can be managed with lifestyle modifications alone.
So many people just don't care though. They really don't. Fast foods, red meat, soda, alcohol, candy, fried stuff, sugar, etc. And no exercise. People don't want to change until they develop a chronic disease as a result of their habits, but sometimes not even that is enough. It's unfortunate but it's the current reality.
