Americans are disgustingly fat. I'm allowed to say so because not long ago, I was disgustingly fat.

Three years ago, I weighed close to 300 pounds. I would like to tell you being a big, lazy slob was awful, but it wasn't. I enjoyed massive portions of rich, delicious foods and took great pleasure in passively watching the shiny flat-screen TV in front of my leather couch. It was not such a terrible life.

It was also incredibly selfish.

Things changed for me when I fell in love with a girl who wasn't fat. She's a nurse, and she explained the many reasons I needed to lose weight. So I did. It wasn't that hard, really. I restricted my calories and got some casual exercise. It took eight months to drop 100 pounds. I've slowly taken off another 10 pounds or so since. I did not set foot in a gym or eat any weird berries; I adhered to a common-sense diet that fit my lifestyle. If you want to hear more about the diet, I wrote a book about it, Chubster, that came out last week.

Dieting was, for me, a reasonably pleasant experience. I'd describe it as the kind of surprisingly not-so-horrible chore you wonder why you allowed yourself to avoid for so long. Like taxes or dental work, other blandly irksome tasks that people procrastinate about for reasons you can't understand once you're on the other side.

Yet two-thirds of American adults are overweight or obese. Why?

Being fat is a choice. Genetics plays a role, sure. So does your upbringing. But you do not get fat unless you're eating more than you need to nourish your body. That's basic science. There are no excuses, no matter what someone from the so-called Fat Acceptance Movement wants to claim. Not that you can totally blame people who get discouraged and give up, inevitably leaving their loved ones or the government to care for them when the bill comes due.

There's a $60 billion industry of Organized Dieting that exists to sell people schemes and gadgets. Most of the things they're selling are bunk because the truth is too simple to market.

Our bodies are machines; food is their fuel. Since the early 1900s, we've known how much fuel various foods contain and how much bodies of various shapes and sizes need. In 1918, the first modern diet book, Dr. Lulu Hunt Peters' Diet and Health, With Key to the Calories, sold two million copies by explaining that the calorie is a measurement of food energy and that people gain weight because they're taking in too much fuel. This is too easy, of course. It's been parsed thousands of different ways since, often with the basic science of the matter obscured in the process.

Worth remembering with foodie gluttony cresting: People aren't fat because they eat fast-food hamburgers, wheat bread, too much meat, too little meat or gingerbread. They're fat because they eat too much, period. It's quite possible to get fat from artisan charcuterie or tofu scrambles.

We can have sincere debates about our food systems—hyper-efficient, factory-style farms or the organic localist approach, and whether it's OK to eat animals if you kill them yourself—but few arguments seem to address how we can develop a food system that will end the obesity epidemic.

I think we're at the point where that needs to change. I hope we're ready to take a clear-eyed look at the problem.

It starts deep in our DNA. Evolution has fine-tuned the human body for the lifestyle of a tribesman engaged in hunting-gathering and subsistence agriculture. Your body's natural inclination is to get and store whatever fat you can because you never know when a hard, cold and hungry winter is coming.

"For centuries, the human race struggled to overcome food scarcity, disease, and a hostile environment. With the onset of the industrial revolution, the great powers understood that increasing the average body size of the population was an important social and political factor," writes Dr. Benjamin Caballero, a Johns Hopkins University professor.

So we, as a society, put an emphasis on producing and distributing cheap, high-fuel food. By the year 2000, we reached what Caballero calls "one of the major achievements in human evolution"—having more overweight people than underweight people for the first time in human history.

Fatness is a byproduct of the leisurely life our hardworking ancestors and the greatest minds of the Western world have been working to create for millennia. They wanted for us a life of plenty, without back-breaking work. Our overweight society is, by the standard of the ancients, a utopia.

Yet it's not working. We're at a point where life expectancy is actually falling in parts of the country. Do people seem happier? Humans aren't meant to sit limply on soft chairs, imprisoned by our own fat, we're meant to be actively engaged in the outside world. The irresponsibly overweight are also counting on someone—their kids, spouses or our overstrained social services—to pick up their mess when the effects catch up to them.

Turns out, burgers and fries are fine when you're working in factories, but not so much after the post-industrial economy picked people off the assembly line and plunked us down in cubicles. And yet our habits—what we eat, how we get around—haven't evolved to match our new reality.

That can't change overnight. It will, eventually, I'm confident. Just like it did with smoking, still the country's leading cause of preventable death but half as common as it was in the 1960s. Foods will get lighter, perhaps aided by new technology—look at the miracle of Popchips. Urban planners will build cities that get people on their feet. Portland is getting there quickly.

Responsible people can't sit idly waiting for macro change, though. For the fat, that starts by admitting your weight is a byproduct of your choices. Then it's a matter of recognizing those choices are unsustainable. I realized if I didn't change my life, I was going to die—but not before burdening the people I loved and our hospitals, and not before missing out on the life I could have been living. 

Too many diet pitches start with the premise that being fat is terrible. It isn't, really. In contemporary American society, it's perfectly possible to live a happy life as a big, fat slob. It's also disgusting—not aesthetically, but morally—and don't blame anyone for saying so. There is life behind the flatscreen. Get off the couch and start living it. 

GO: Martin Cizmar signs copies of Chubster at Powell's City of Books, 1005 W Burnside St., on Thursday, Jan. 12. 7:30 pm.