Everyone wants to blame the government or big pharma, but I think the fact of the matter is, human beings are evolved for a world that is very different from the one we currently live in. At least my perspective, this explains the situation much better.

Humans evolved in an environment where there were no highly processed sugars or highly processed carbohydrates and where our long ago ancestors got daily exercise looking for food, building shelters, running or fighting predators and so on. The human body is optimized for a certain type of diet and a certain level of exercise. In addition to this, human beings evolved to crave sweet food and eating sweet food is an enjoyable experience. We know that eating highly processed carbohydrates or sweets leads insulin to rise more than eating other things and doing this repeatedly over time leads to fat accumulation, insulin resistance and diabetes.

Contrast with the world we live in today: sugary drinks and foods and processed carbs are everywhere. Many of us are required to sit all day (or at least be stationary, if not sitting) for our jobs. To get food today most of us either drive to the grocery store, drive to a restaurant, or have food delivered to our home. We don't build our own homes. We don't hunt. We don't fight off predators. There is very little that many of us have to do in modern life that requires exercise. Almost all exercise is optional.

Another thing to consider, is that the amount of stress we encounter in daily life has not gone down. If anything, at least in the developed world, we have ramped up the amount of stress that people experience on a daily basis in the past few decades. Stressful commutes, office politics, fighting the crowds while out shopping, constantly being prodded to compare yourself to everyone around you (i.e. social media) and poor sleep (and then overindulging in caffeine the next morning) are all parts of modern life. Consider that the stress response evolved in living things in order to get that living thing in to action, to flee or fight for its life. As it turns out, the physical activity that follows a stress response usually turns off the stress response.. but the times we find ourselves in stressful situations often do not offer a physical outlet for our stress. Thus, cortisol remains elevated in many of us, and it turns out that consistently high cortisol leads to insulin resistance.

So two hormones being persistently elevated lead to insulin resistance: insulin and cortisol. These hormones are persistently elevated in the average human in the developed world. Exercise improves insulin sensitivity but most humans in the developed world have no reason to exercise, aside from attracting mates and staying healthy.

Lastly, one's ability to forego pleasure or leisure now for a return later (or, for the promise of not getting sick later) varies a lot throughout the population. Some people are very good at this, some are not. Obviously the amount of education and knowledge one has also varies from person to person in the developed world. Since most of us crave sweets and processed carbs, they are readily available and nothing in our lives requires us to exercise, those who are not good at forgoing pleasure now or those who do not know that eating this way is bad for you, will sit and eat like garbage right now because it feels great right now.

It is not a simple explanation, but to me, this set of facts explains why it is becoming more of a problem as time goes on. As much as big pharma may want people to get sick and buy their drugs, big pharma didn't make people crave sweet food, nor did they make processed food ubiquitous, nor did they come up with office jobs that keep us sedentary, nor are they keeping us stressed out. These are all byproducts of evolution and our own technological successes.