People can be obese but metabolically healthy and fit, with no greater risk of developing or dying from cardiovascular disease or cancer than normal weight people, according to the largest study ever to have investigated this seeming paradox.
The findings show there is a subset of obese people who are metabolically healthy — they don’t suffer from conditions such as insulin resistance, diabetes and high cholesterol or blood pressure — and who have a higher level of fitness, as measured by how well the heart and lungs perform, than other obese people. Being obese does not seem to have a detrimental effect on their health, and doctors should bear this in mind when considering what, if any, interventions are required, say the researchers.
“It is well known that obesity is linked to a large number of chronic disease such as cardiovascular problems and cancer. However, there appears to be a sub-set of obese people who seem to be protected from obesity-related metabolic complications,” said the first author of the study, Dr Francisco Ortega (PhD). “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 lower risk of diseases or premature death.”
Dr Ortega is currently a research associate affiliated to the Department of Physical Activity and Sport, University of Granada (Spain), and at the Department of Biosciences and Nutrition, Karolinska Institutet (Stockholm, Sweden); but the project and investigation took place at the University of South Carolina (Columbia, USA) under the direction of Professor Steven Blair, who is responsible for the long-running “Aerobics Center Longitudinal Study” (ACLS) which provided the 43,265 participants for this current analysis.
The participants were recruited to the ACLS between 1979 and 2003. They completed a detailed questionnaire, including information on their medical and lifestyle history, and they had a physical examination that included a treadmill test to assess cardio-respiratory fitness and measurements of height, weight, waist circumference, and their percentage of body fat. Body fat percentage (BF%) was measured either by calculating the amount of water displaced when the person was completely submerged (the method that is considered the most accurate), or by taking the sum of seven skin fold measures (when folds of skin are pinched between measurement callipers). Blood pressure, cholesterol and fasting glucose levels were also measured. The study participants were followed until they died or until the end of 2003.
Dr Ortega and his colleagues found that 46% of the obese participants were metabolically healthy. After adjusting for several confounding factors, including fitness, the metabolically healthy but obese people had a 38% lower risk of death from any cause than their metabolically unhealthy obese peers, while no significant difference was seen between the metabolically healthy but obese and the metabolically healthy, normal weight participants. The risk of developing or dying from cardiovascular disease or cancer was reduced by between 30-50% for the metabolically healthy but obese people, and there were no significant differences observed between them and the metabolically healthy, normal weight participants.
“Our study suggests that metabolically healthy but obese people have a better fitness level than the rest of obese individuals. Based on the data that our group and others have collected over years, we believe that getting more exercise broadly and positively influences major body systems and organs and consequently contributes to make someone metabolically healthier, including obese people.
Read more: Science Daily