You've just had a heart attack, and you're in the ambulance on the way to the hospital. If you're overweight or moderately obese, you're actually more likely to survive that heart attack than if you were a normal weight or underweight person.

It's what doctors and researchers call the "obesity paradox." While being overweight probably helped land you in the hospital with a heart attack in the first place, that extra weight could work in your favor after the fact. In fact, dozens of studies from the past several years indicate that people who are overweight or moderately obese according to the body mass index are more likely to survive chronic conditions like cardiovascular disease, kidney disease and diabetes than normal weight or underweight people.

But whether the obesity paradox is a real phenomenon with a yet-to-be-discovered biological basis or just a statistical fallacy drawn from bad data is up for (angry) debate.

NOT BLACK AND WHITE

In the "fat as protection" camp is Dr. Kamyar Kalantar-Zadeh, a professor in the School of Medicine at the University of California, Irvine, as well as an obesity paradox expert.

"It's very provocative to go out and say obesity isn't as bad as we thought -- to announce to the world that there are good things about obesity, too," Kalantar-Zadeh told The Huffington Post. "But the truth is that there is [an] emerging set of data over the past several years suggesting that obesity is not as black and white as we have maintained for the past 30 to 40 years."

Kalantar-Zadeh wrote an editorial in the journal Mayo Clinic Proceedings that compared the obesity paradox to a bad friend whose influence lands you both in jail. You wouldn't be there in the first place if it weren't for that bad friend -- but once in jail, that friend protects you from bad conditions and other inmates. The effects of the obesity paradox are especially pronounced in old people and those with acute and chronic diseases, Kalantar-Zadeh wrote.

"I don't let my kidney disease patients and patients on dialysis lose weight," Kalantar-Zadeh said to HuffPost. "If I tell your 91-year-old grandma to lose weight, am I helping her or hurting her? This is all about who benefits from losing weight, and who doesn't."

Kalantar-Zadeh's editorial accompanies two new studies in the journal that shed more light on the obesity paradox. The first, a meta-analysis of 36 different coronary heart disease studies by Dr. Abhishek Sharma of the State University of New York Downstate Medical Center, confirms what researchers have been saying for several years now: Coronary heart disease patients with a BMI between 25 and 30 (technically "overweight") have a lower risk of dying from cardiovascular disease than normal weight patients with a BMI between 18 and 25.

In fact, obese and severely obese patients with cardiovascular disease had 27 percent and 22 percent lower chances, respectively, of dying from any cause compared with people with normal BMIs.

The second, an observational study of almost 48,000 heart surgery patients that was led by Dr. Carl Lavie of the John Ochsner Heart and Vascular Institute, digs a little bit deeper into the paradox. Instead of simply using body weight to compare patients, Lavie used a formula to estimate both the patients' body fat percentage and lean mass percentage (organs, bone, muscle) and compared those characteristics.

He concluded that it's the healthy lean mass -- not fat -- that could be protecting patients once they suffer from a cardiovascular outcome. In fact, higher lean body mass was associated with 29 percent lower risk of death.

WRONG DATA, WRONG CONCLUSIONS?

A lot of data supporting the obesity paradox would disappear if researchers followed Lavie's example and relied on more comprehensive data points than simply BMI, said Dr. Jonathan Myers, a clinical professor at the Stanford University School of Medicine and health research scientist at the VA hospital in Palo Alto, CA.

"One of the problems with the obesity paradox is that we've been making the wrong measurements," Myers told HuffPost. "Most of these studies only have BMI available, and what we really want to measure is body composition -- namely, how much visceral fat you have, which is associated with high metabolic risk."

One simple and cost-effective way to more directly measure body composition is to take a patient's waist circumference, Myers said, since the amount of visceral (abdominal) fat is a better predictor of disease than how much a person weighs.

Another simple explanation for the obesity paradox could be that researchers aren't taking into account a person's fitness level. Myers and other investigators have done extensive research showing that the obesity paradox is not seen among individuals who are fit. And as a scientist at the VA hospital, Myers runs into another possible explanation for the obesity paradox all the time -- something he and his colleagues call the "veteran effect."

Career military folks have to maintain certain weight and athleticism, Myers explained, which staves off obesity and its complications for many years beyond the average American. But even if that military member ends up becoming overweight or obese after leaving the armed forces, his or her metabolic markers are a lot healthier than someone with the same weight.

"They've spent most of their adult life pretty healthy and reasonably fit," Myers explained. "We see the 'obesity paradox' with them, simply because they haven't been exposed to the risks of obesity long enough."

In his meta-analysis on obesity and coronary heart disease, Sharma outlines other possible explanations for the so-called paradox. He suggests:

Obese people tend to have coronary heart disease earlier in their life, and it's their young age that helps them survive --not necessarily their weight.

Underweight and normal weight patients might have heart disease because of underlying genetic factors, which potentially leaves them worse-off than overweight patients who acquire the disease because of lifestyle factors.

Overweight and obese people might receive better medical care. Because of their size, doctors might be more diligent in prescribing overweight patients more heart medications at higher doses than normal weight patients.

The biggest thing to remember about the obesity paradox, concluded Myers, is that researchers are observing the phenomenon in clinical populations, not the general population. That means the people in these obesity paradox studies are already sick, and that a healthy person shouldn't decide to pack on the pounds based on this research.