By JOHN KELLY

The Washington Post

I can pinpoint the exact date our nation’s obesity epidemic began. It was in the spring of 1988, and it all started with a little plastic drinking straw.

Well, not so little, actually, which is why I have such a clear memory of the events I am about to describe. I was driving and suddenly became famished. I pulled into a McDonald’s.

It was all routine, the food reassuringly familiar. What was different was the straw. It was bigger — had a wider diameter — than any drinking straw I’d seen before. It felt odd between my lips, as if someone had replaced a toothpick with a drum stick.

I eventually became accustomed to the bigger straw. We all did, just as we would eventually become accustomed to the bigger us. But when I ask friends about this — when I say “Do you remember The Day the Straws Got Big?” — I get blank looks.

So I decided to look into this. I found that, yes, you can divide modern U.S. soda consumption into BBS and ABS: Before Big Straws and After Big Straws.

First, though, let us look at the history of the modern drinking straw. It was patented in 1888 by an Ohioan named Marvin Stone.

“He basically invented it just thick enough so no lemon seeds would come into the tube,” said Chrissy Rapanos, a senior market research analyst at Dart Container, one of the country’s largest manufacturers of straws.

Stone was tired of getting seeds in his mouth when all he wanted was a refreshing sip of lemonade. He also didn’t like the grassy taste from the natural straws commonly used in the 19th century: lengths of dry, hollow rye grass.

Stone’s solution was to create a tube from a spiral of paper. For decades, that’s what Americans used: paper straws with a diameter just a little smaller than a typical lemon pip.

The next innovation came in 1937, when Joseph Friedman invented the bendy straw. Things were quiet on the straw-technology front until the 1960s, when plastic straws started to replace paper ones.

And then, around 1988, the plastic straws got wider.

There is some speculation in straw circles that this can actually be traced to milkshakes, not sodas. Allegedly, McDonald’s shakes were so thick that narrower straws collapsed when customers tried in vain to suck them.

No quick-service restaurant likes to maintain multiple utensils, and so the same straws were used for all beverages. (McDonald’s politely declined to comment on the size of its straws.)

Here are the categories and sizes that most American straw manufacturers use: milk (0.15 inches in diameter), jumbo (0.21 inches), super jumbo (0.24), giant (0.28) and colossal (0.47 inches and used mostly for bubble tea).

My observation is that in the late 1980s, fast food restaurants went from jumbo to giant. A bigger straw means more consumption of beverage, said Janine Madden, who works for Precision Products Group, a company whose holdings include Stone Industrial in College Park, Md., descendant of Marvin Stone’s original straw-making company.

Obviously, correlation does not imply causation. I guess a stickler might point out that it wasn’t the bigger straws that made Americans fat, it was the bigger sodas.

Or maybe it was our cool Camaros, which made us want to drive everywhere rather than walk.

Or our engrossing TV shows, which made us want to stay at home in front of the boob tube.

Or our convenient and delicious fast-food restaurants.

Any one of those could have been the last straw.