Here’s one more reason to keep that New Year’s resolution to lose weight: your survival may depend on it.

New research suggests that people who are extremely overweight are at a higher risk of dying early — even if they are deemed physically fit.

Swedish scientists launched a massive study to test a widely held belief that being highly fit can offset the potential for fatal illnesses that come from obesity.

Their findings, published in the International Journal of Epidemiology, dispel a common theory that it’s possible to be “fat but fit.”

Apparently, weight is the most important factor when it comes to long-term health.

Of the 1.3 million young men who participated in the study for an average of 29 years, those who weren’t fit but who weighed a normal amount were 30 percent less likely to die over the next few decades than the fittest obese men. Being “metabolically fit” meant the participants did not have insulin resistance, diabetes, high triglycerides or high blood pressure and had good cholesterol levels.

The researchers focused on aerobic fitness, using a cycle test to measure their fitness levels by having them pedal until they were fatigued. Obesity was defined using body mass index.

Men with weight in the normal range, regardless of their fitness level, appeared to have a lower risk of death compared to those who were obese but fit. Even more striking: the beneficial effect of high aerobic fitness appeared to be reduced with increased obesity. In fact, those at the most extreme in terms of obesity did not see a benefit at all from aerobic fitness.

The researchers said the findings suggest that being obese may reduce the protective effects of being fit: “This data does not support the notion that ‘fat but fit’ is a benign condition.”

According to the World Health Organization, the higher the BMI, the greater the risk of diabetes, heart disease and some cancers.

“It’s clear that both fitness and fatness are important,” said Walter Willett, an expert on nutrition and health at the Harvard School of Public Health. “It’s definitely good to be as fit as possible no matter what your body weight. But it’s also clear that it is optimum to be both lean and fit.”