That estimate of how much the nation’s chubses are wasting in gas comes from a study by Sheldon Jacobson, professor of computer science at the University of Illinois and director of the school’s simulation and optimization laboratory.

“The key finding,” reports Jacobson, “is that nearly 1 billion gallons of fuel are consumed each year because of the average weight gain of people living in the United States since 1960 — nearly three times the total amount of fuel consumed by all passenger vehicles each day based on current driving habits.”

On average, we’re up in weight per capita in the U.S. since 1960 by 24 pounds, the size of a nice Thanksgiving turkey.

Officially, the federal government says that 62 percent of us are “overweight,” and probably 99 percent of us would say the government’s too fat, so we’re more than even. It’s fat city, all over.

At the pump, the extra fat is costing $7.7 million a day, or $2.8 billion a year, according to a University of Illinois news release, noting that these increased gas expenses are “linked directly to the extra drain of body weight on fuel economy.”

Jacobson didn’t skip those tubby kids in the back seat with their M&M’s. In tying the number of pounds of fat to poor mileage, he counted drivers as well as passengers.

What he didn’t count in his 938-million-gallon estimate is the impact of those two million drivers who operate America’s heavy trucks and tractor-trailers, those guys on the turnpike with a bucket of KFC extra- crispy on the seat and a two-foot hoagie from Pizza King. Jacobson’s study, funded by the National Science Foundation, considered only the effect of blimpos in cars and light trucks used for noncommercial purposes.

Jacobson’s estimation of the societal cost of fat in gallons may have also underestimated the size of the problem in a couple different areas. I don’t see anything in his study about how bigger people might tend to buy bigger cars, cars that go fewer miles per gallon no matter what the weight of their occupants. Just on anecdotal evidence, I don’t see a lot of super-sized people stuffed into those environmentally friendly MINI Coopers.

There’s also no estimate in the study about how food addicts might drive more, such as heading off at midnight to Dunkin’ Donuts for a quick fix while their skinny neighbors are tucked under the covers, or driving to Foodland more times than their scrawny neighbors because they’re always running out of food.

In any case, nearly a billion gallons a year is bad enough. “Beyond public health,” explains Jacobson, “being overweight has many other socioeconomic implications.”

It’s the public’s business, in other words, if you’re too fat. A generously proportioned physique equals less gas mileage, more oil imports, and more money exported to al-Qaeda.

With socioeconomic impacts on the table, there’s nothing on one’s table that isn’t everybody’s business, nothing that’s beyond the reach of the planners, the regulators and the socioeconomic administrators.

George Washington University law professor John Banzhaf III, for instance, argues that plump patients should consider lawsuits against doctors who didn’t provide sufficient warnings about the downside of obesity and that parents of fat kids could well be fair game at the courthouse if they didn’t sufficiently limit trips to Dairy Queen.

Or food companies can be made the target, as when two teenage girls in Brooklyn — combined weight, 440 pounds — sued McDonald’s, claiming that the company made them fat. Or we could make 7-Elevens close at 2 a.m., like taverns, so no one could sneak out for a Snickers in the middle of the night.

Arguing that it’s time we “get away from these arguments about personal responsibility,” Yale University’s Kelly Brownell recommends a 7 percent to 10 percent “Twinkie tax,” a fat tax on calorie-dense foods.

With even less red tape, instead of the government’s measuring the sugar and nutrient content of every cheeseburger and every type of nacho dip, the IRS could just weigh taxpayers and charge them by the pound.

Charge a 300-pounder making $50,000 twice as much as a 150-pounder with the same income and the fatso will have plenty of incentive to shed some pounds and expand America’s fuel efficiency.

Ralph R. Reiland is an associate professor of economics at Robert Morris University in Pittsburgh.