Envious of that skinny friend who always seems to be able to eat whatever she wants without ever gaining any weight? Well, according to some startling new research, that characteristic might not be as great as it sounds, reports the Daily Mail.

Skinny people with faster metabolisms tend to have significantly shorter lifespans than people who burn calories more slowly. The research could forever change the way scientists understand our metabolic rates and how that affects our health and fitness.

The findings, which were presented by scientists from the National Institutes of Health, were based on a study of more than 600 healthy Pima Native American volunteers. Researchers measured how quickly the subjects' bodies converted food into energy over a 24-hour period. The measurements also included a look at the subjects' resting metabolic rate, which is the amount of daily energy expended while an individual is at rest. The resting metabolic rate essentially measures how much energy the body requires just to keep vital organs functioning.

"We found that higher endogenous metabolic rate — which is how much energy the body uses for normal body functions — is a risk factor for earlier mortality," said researcher Dr. Reiner Jumpertz. "This increased metabolic rate may lead to earlier organ damage."

In other words, the faster a person burns calories in non-exercise related activities, the faster the person ages. The study did not find a similar correlation between lifespan and metabolism when researchers considered calories burned from exercise.

"[Exercise] clearly has beneficial effects on health," Jumpertz said.

The study's results may not come as a big surprise to animal researchers, who have long noted a strong link between lifespan and metabolic rate in animals. Small creatures with quick metabolisms and rapid heart rates, such as mice, have much shorter lifespans than animals with slow metabolisms and heart rates, like elephants. Humans fit into that spectrum as a species too, but until now there has been little evidence linking metabolic variance within a population of humans with lifespan.

Though this study may make having a slow metabolism a bit easier to swallow, it still discourages eating too much high-calorie junk food that we all love. Those with slow metabolisms who become fat might not benefit from a longer lifespan because obesity can increase their risk of heart disease, stroke and diabetes.

Want to live longer? You're still going to have to work for it — and that means plenty of exercise and healthy eating.

Bryan Nelson ( @@brynelson ) writes about everything from environmental problems here on Earth to big questions in space.

People with fast metabolisms have shorter lifespans
The ability of some skinny people to consume lots of calories without gaining weight might come with a cost.