New research suggests that obesity does not guarantee poor health or an increased risk of heart disease and cancer - and in fact over 40 percent of obese people could actually be metabolically healthy.
A report published in the European Heart Journal, the largest ever to have investigated this subject, assessed data from over 43,000 participants in America's long-running Aerobics Center Longitudinal Study (ACLS) between 1979 and 2003.
The results showed that 46 percent of obese participants were, in fact, metabolically healthy - and thus did not suffer from conditions such as high blood pressure, high cholesterol, diabetes and insulin resistance.
After adjusting for several confounding factors, including fitness, the metabolically healthy group had a 38 percent lower risk of death from any cause than their obese peers.
Furthermore, the metabolically healthy group had a markedly higher level of finess, based on heart and lung performance, than other extremely overweight people.
Participants in the ACLS completed a detailed questionnaire, including medical and lifestyle history, before taking part in a detailed physical examination and fitness test. Their body fat percentage was also measured, along with blood pressure, cholesterol and fasting glucose levels.
The research was carried out by a team at the University of South Carolina, under the direction of professor Steven Blair. Dr Francesco Ortega, first author of the study, said: "It is well known that obesity is linked to a large number of chronic diseases such as cardiovascular problems and cancer.
"However there seems to be a subset of obese people who seem to be protected from obesity-related metabolic complications. They may have greater cardio-respiratory fitness than other obese individuals, but, until now, it was not known the extent to which these metabolically healthy but obese people are at a lower risk of diseases or premature death."
"Our study suggests that metabolically healthy but obese people have a better fitness level than [other] obese individuals."
Dr Ortega concluded by stressing that "getting more exercise broadly and and positively influences major body systems and organs and consequently contributes to makes someone metabolically healthier, including obese people. In our study we measure fitness, which is largely influenced by exercise."