How well do we know our bodys? We could say it depends on the time and the place. Much of the time, I have a pretty one-dimensional view of my body - that is to say, I'm not really aware of it at all. When I'm busy at work say or engaged in some pressing intellectual problem (chips open or wrapped?). Other times, I have a more 'two-dimensional' view. Looking in the mirror, looking down at myself, looking at images of other people, seeing the surface, not really interested in what is going on inside. This is probably how much of us spend our time - we are visual creatures after all - and physical appearance still forms much of our judgements and ideas about ourselves and others.
Then there is the more 'three-dimensional' knowledge of the body. This includes awareness that we have an 'inside' as well as an outside, which can be raw physical sensation, say a pain or ache, or intellectual - anatomy, biochemistry, the 'systems' of the body. This type of knowledge is often the reserve of health professionals: doctors, nurses, physiotherapists, radiotherapists, radiographers and pharmacists, though really nowadays anybody can understand the basics if you know where to look. Unfortunately there's a lot out there - half-baked health faddism, media scares and the like - which provide a lot of heat but little light, so one needs to be cautious (a rule of thumb is to avoid those sources that divide all known matter into that which does and that which does not give you cancer).
We now have detailed 'three-dimensional' knowledge down to the genetic level, and this has brought significant benefits in treatments of disease. However this depth brings limitations also. The specialization of medicine has been at the cost of public and preventative health (as well certain economic interests). Nowhere is this more apparent than with the various 'epidemics' now building up in most countries, mainly diabetes, cardio-vascular disease and dementia. Despite the enormous burden of these conditions for the patients, their loved ones and health systems, the traditional medical response has not been able to keep up.
In getting a better understanding of our bodies we need to also appreciate the 'forth' dimension, that of time; in particular evolutionary time. Our bodies did not simply wash up on the 21st century with a cigarette in one hand and a cheeseburger in the other. We are the product of millions of years of evolution. (For more detail on this you can check out The Story of the Human Body by Daniel Lieberman, 2013).
The most important factor when we look at evolution is how we get our energy. If we consider our closest ancestors - the great apes - we see that their energy, and protein, comes almost entirely from plants. Nowadays it is easy enough to get all of our nutrition from plant sources but for our ancestors the amount of time spent eating plants - chewing and digesting - limited how much time they could spend doing other things and even how much their brains could grow due to the pressure their powerful jaw muscles placed on the skull.
If we go forward a few million years we see that our hunter-gatherer ancestors now had the technology to process (i.e. cut and cook) food which made getting the necessary calories a lot easier - digesting food requires quite a bit of energy. Our ancestors' skulls were also less heavy-duty as a result, allowing space for the brain to grow and for us to produce language. We still got most of our diet from plants - in the hunter-gatherer dynamic, it was the gatherers who did the most work - with a little meat or fish now and again. The important thing to remember is that it took quite a bit of work getting enough energy out of the environment. As a result the human body has evolved to be super fuel-efficient.
We then had our agricultural revolution, which gave us relatively bountiful energy in the form of simple carbohydrates, and in the 21st century industrialization has made calories readily available - mainly sugars and simple carbs. Yet we still have the bodies of our ancestors: super efficient, evolved to eke out every last drop of energy from the food we eat either to use up or store.
Another inheritance is that we have evolved to walk pretty much everywhere - we used to clock up around 7 miles a day on average - with the occasional jog thrown in or run if one was feeling energetic. Walking is efficient, so is running. Both actions use momentum and the natural springiness of the body for maximal efficiency, ideal examples of 'the wisdom of the body'. Yet we don't walk as much as we used to and in general we are not as active: a walk through most modern cities or suburbs will show most people driving - or catching the bus - to work, work which is largely sedentary at that and free time is similarly largely spent sat down.
This is not the place to judge sedentary lifestyles and eating habits. External conditions often makes these choices for people and it is difficult to get active after long hours at work or child-care. However there is no doubt that abundant calories - often with little else nutritional - and low physical activity is causing the majority of health issues in the West. Take excess calories; the body will hoard all those calories for a rainy day, hence obesity. It will become less sensitive to those calories as it only needs so much - hence diabetes. And those excess calories - the fat and the sugar - remain in the system causing damage - hence cardio-vascular disease.
Moreover the golden rule is that 'if you don't use it you lose it'. The human organism will not waste precious energy on things that aren't being used: if muscles aren't worked they will weaken, likewise bones or the heart, and even mental capacity: the brain uses a lot of energy, about a quarter of the supply. Unfortunately we have a fatalistic view of aging that says after a certain age the body inevitably gets weaker, that it gets 'harder to learn', as though the human organism were a piece of clay that slowly dries up over a lifetime. Yet while it is true we age, a lot of what we think of as inevitable decline is actually de-conditioning.
Overlooking all of this causes problems. I am certainly not the only doctor who finds it depressing to see so many people getting unwell from preventable and reversible lifestyle factors. It is also frustrating that our response as a profession is to almost always treat the symptoms rather than the cause, and almost always this involves medication. We overlook the simple lessons of evolution - our bodies are efficient; we are meant to be active, we are meant to be thinking, communicating, social.
However the issue is not so much that we have fallen out of harmony with our man-made environment or even with the natural world. I think we have, but there is only so much we can do about that. The issue is that we have fallen out of harmony with ourselves. The good news is that it does not take much to re-connect. Mindfulness about what we eat seems to be increasing and in terms of activity there is something out there for everyone. People are becoming more proactive - cycling to work, working out in parks and so forth. (Eventually the medical profession will catch up I'm sure.) The important thing is not to put too much force into what you do. It is easy to fall into the trap of becoming attached to effort or exercise, or the right diet, or ideas of purity and detoxing, or health. The starting point is always to trust your body, to know it is always changing and adapting, and not to get attached to 'ideas' about it - harmonise yourself to your body and the rest will follow.