If that were true about the human condition in the same way that it’s true for conservation of mass, we wouldn't be living longer and healthier lives than our forebears. Yet here we are.
Of course we should be aware of side-effects. But there’s no law of nature that says there have to be any serious ones.
Take out infectious disease, post-partum maternal deaths, no sanitation, and obvious lifestyle choices like smoking, and are we really living healthier lives than prior generations? I'm not so convinced.
Those things you list are the bits which made our lives healthier. Just because you can list them doesn't mean they didn't happen.
Now I'll take our modern scientific advances over not having them. Give me modern sanitation, surgery, antibiotics, and vaccines for sure. But I'm not sure I'd call the way many American elders around me are living in their 70s to be healthy lives. Many lack mobility, are obese, are on a fistful of prescription drugs daily, and have constant pain. Except for the ones that ate well and in moderation, didn't drink much, and exercised their entire lives.
I just hope people take these GPL-1 drugs but also get their bodies moving (particularly strength training).
I think we need a huge investment in physical therapy. Everyone who is obese and working to reduce their weight and increases their activity needs PT, and we need PT specialists who know how to work with heavy people. I know a lot of fat people (including myself) who get injured and discouraged trying to follow workout advice intended for people in substantially better physical condition, and also a lot who have had trouble finding trainers or physical therapists who know how to work with them.
And also totally agree that we need to invest in PT and educating PTs on how to work with people in larger bodies. As a formerly unhealthy person who only found exercise in their 30s, it's ridiculous to me that my high school gym requirements didn't teach me how to safely lift weights or use a gym. They would just let us use a barbell without any proper training, and the first time I tried to bench press with some friends (because we probably saw someone in a movie doing it) I injured myself. Every high school student should be learning how to use a gym, get through a yoga class, learn some calisthenics, etc. Set them up for their life so it's not so intimidating as an adult. Instead, at least for me in the 90s, it was a lot of playing basketball and baseball, nothing to keep me healthy on my own in my life.
Not saying it’s easy, and no it isn’t as simple as calories in, calories out, but it is close to that simple. Working out, running, weightlifting, all that can happen later. Eating “right” and just walking a lot can induce a lot of positives.
I'm always around 12-13% body fat, but to get them to show, absolutely, it's all diet. I'm vegetarian, so that probably works against me, but I've never had that 8% body fat ripped look even with all the activity I do in a week.
John Adams: 90
Samuel Adams: 81
Benjamin Franklin: 84