"Metabolically fit", scientists explained, means the person exercises regularly, has no high cholesterol, no high blood pressure, or raised blood sugar.
After analyzing 43,000 Americans, the results, which were published in the European Heart Journal, showed that even though some individuals are classified as overweight, it may not necessarily mean that they are in danger of any health issues.
Out of all the participants, 18,500 were obese, while half had lab tests and physical exam results revealing that they were metabolically healthy. Tests also showed that these people were not suffering from diabetes, high blood pressure, high cholesterol, and were generally fitter and even exercised more than the other obese subjects.
These participants had half the risks than "metabolically less fit" obese people, and an identical risk of developing or dying from cardiovascular disease or cancer compared to those of normal weight.
The research suggests that although a person may be a little on the heavier side, they can become healthier with more exercise, Dr. Francisco Ortega, lead author, said. "This research highlights once again the important role of physical fitness as a health marker."
Amy Thompson, from the British Heart Foundation, added:
"These studies remind us that it is not always your weight that's important, but where you carry fat and also how it affects your health and fitness.
"In the majority of cases, obesity is an undeniable risk factor for developing coronary heart disease. However, these studies remind us that it is not always your weight that's important, but where you carry fat and also how it affects your health and fitness.
The research does have some limitations, however. Since most of the subjects came from a similar background, being well educated, Caucasian, and working in executive or professional jobs, the results may not apply to everyone.
If you have a bit of extra fat around the middle of your body, it is especially important to be aware of your weight, Thompson explained, because there, the fat cells are really active and produce toxic substances that cause damage; potentially leading to heart disease.
Amy Thompson revealed that in order to slim down and decrease the risk of heart health issues, you need to eat healthily and be physically active.
She concluded with a message for readers:
"Don't get too caught up on the numbers on the scale. Calculating your body mass index and measuring your waist are great ways to keep on track. If you are concerned about your weight and want to make changes to your lifestyle, make an appointment with your GP to talk it through."
Written by Sarah Glynn