The largest generation may now be the fattest generation ever. And that spells trouble for the healthcare system.

Studies show that baby boomers — 81 million born between 1946 to 1964 — are losing the battle of the bulge. About a third of boomers are obese and an additional 36 percent are overweight, according to a new Associated Press-LifeGoesStrong.com poll. That makes them heavier than the generation that precedes them and the one that follows them.

Also, only half of boomers say they exercise regularly, and 37 percent don’t do any strength-training at all, a vital activity to fight the muscle loss that comes with aging.

Like most boomers, Leslie Aronson discovered that gaining a pound here and a pound there eventually adds to many pounds everywhere. Now, she faces an uphill struggle to shed the excess weight around her middle — a struggle most baby boomers share.

“I never had a weight problem until my mid-40s,” says the 53-year-old nurse from Kendall. “We don’t go to Burger King or [eat] fast food. We eat healthy. We don’t eat big portions, but I’m still having an issue.”

While the AP poll is based on participants’ self-reported height and weight, at least one other government study has confirmed the troubling trend. In a 2007 National Center for Health Statistics brief, 40 percent of men 40 to 59 years old — a group mostly made up of boomers — were obese. Men younger and older were slimmer. Only 28 percent of 20- to 39-year-old men and 32 percent of men 60 years and older were obese.

Boomer women were no better off. Forty-one percent of women 40 to 59 years old were obese, compared to 30.5 percent for both younger and older women.

Those extra pounds make boomers a medical time bomb — putting more pressure on a medical system already burdened with people living longer — because being overweight puts a person at higher risk of serious chronic conditions.

“We are going to be overwhelmed,” predicts Robert Schwartz, chairman of family medicine at the University of Miami’s Miller School of Medicine. “It’s a significant problem that is going to cost a lot of money if something isn’t done about it.”

Taxpayers will most likely foot the bill as boomers, just starting to turn 65, begin to enroll in Medicare, the federal healthcare plan already struggling to plan for the needs of what many have dubbed a “silver tsunami.” Obesity alone adds $20 billion to $34 billion in extra Medicare costs per year, according to a 2009 study published in the journal Health Affairs. Another study showed that preventing obesity in one typical 70-year-old could save as much as $39,000 in healthcare costs for the remainder of that senior’s life.

The majority of people are overweight for one reason: they consume more calories than they expend. For boomers, that equation is also complicated by environmental factors.

“Boomers have a clean-your-plate syndrome,” says Roberta Schwartz Wennik, a Seattle-based nutritionist and author of The Boomer’s Guide to Getting the Weight Off … For Good. “We grew up finishing everything on our plate because there were starving children somewhere, and that concept is very hard to shake.”

And the portion on those plates has grown exponentially just when boomers need fewer calories. Sedentary lifestyles and frequent dining out don’t help. “They’ve kept eating as they used to, but their metabolism has slowed down and they haven’t adjusted to that,” Wennik adds.