Over the past fifty years, Americans have gotten fatter and fatter. By now, some 63% of American adults are overweight, and 26.5% are obese.

Over the time we’ve fattened up, we’ve also been arguing about the cause. It’s dietary fat. It’s dietary carbohydrates. Etc., etc. By now, the story has changed so many times that most people have entirely given up on trying to follow along, retiring to a sort of nutritional relativism: it doesn’t matter what we do today, as, in ten years, we’ll probably be advised to do the exact opposite.

That’s not an unfair position, given that most of the research on both sides of any nutrition issue has tended to be pretty terrible. Our best young minds, and the lion’s share of our grant dollars, have gone to solving cancer and AIDS, not to resolving whether egg yolks are healthful or not. But, in the past five years or so, things have started to change. For whatever reason, the amount and quality of nutrition science research has gone up exponentially. Now, though public knowledge and opinion hasn’t caught up, we’re coming to a scientific picture of obesity as clear as that of any other well-studied biological process.

The rough shape of that consensus points to three main causes of the American (and global) obesity epidemic:

1. Toxic foods like wheat, fructose, and omega-6 fats. In excess, these make us fat and sick, yet they represent an increasing majority of our diet.

2. Deficiency of important micronutrients like choline and iodine. As more of our calories come from those nutritionally empty toxic foods, we end up micronutient deficient (several of which deficiencies lead to obesity directly), while also instinctively eating more to shore up those micronutrient levels (with such overeating leading to obesity, too).

3. Viruses like Adenovirus 36. While you can get fat pretty effectively with just the two steps above, you can do so even more quickly when infected with an obesity-causing virus; AD-36, for example, is found in obese children at rates four to five times children of healthy weight. Here, too, it’s a vicious cycle: toxic foods lead to gut permeability, and micronutrient deficiencies lead to a compromised immune system, both of which leave your body less able to fight off such an obesity infection.

And that’s it. Certainly, a slew of other factors play in, too (things like non-exercise activity thermogenesis). But those three factors explain the majority of the obesity problem. And, increasingly, it looks like they’re implicated in pretty much every other terrible thing that happens to us, from Alzheimers to acne, from cancer to cellulite.

Of course, agreeing on the problem and implementing a solution are completely different issues. Consider the AIDS epidemic, where, despite our strong understanding that sexually transmitted HIV infection is the primary cause of the spread of the disease, the global number of HIV cases continues to steadily climb. With obesity, too, I fear that even agreement among the science, nutrition, healthcare, and public policy crowds may nonetheless leave us far from effectively addressing the problem in the real world.

Still, it’s worth noting that we’re closing in on such consensus, even if a read through Shape or Men’s Fitness would give you no indication of that. As I said, I think we’re simply five to ten years off from popular opinion catching up to the emerging science.

But catch up it will. You heard it here first.