The body mass index (BMI) is a measure that allows us to easily evaluate the concentration of mass in our body and the adequate weight proportion for our height. In general, when our BMI figure exceeds what is considered a normal weight and falls into the obesity or overweight ranges, we are more likely to suffer health problems like cardiovascular diseases or cancer. However, a study published today in Nature Aging suggests that conclusion may not apply to people over the age of 80 in China.
In a research led by Xiaoming Shi, from the Chinese Center for Disease Prevention and Control, 27,000 individuals over 80 years of age were observed, with an average age of 92.7 years and found that, according to their conclusions for this specific group, being overweight and even mildly obese was associated with lower mortality from all diseases, except cardiovascular ones. Specifically, the optimal BMI for the health of the elderly was between 26 and 30.6, when overweight range starts at 25 and obesity at 29.
This finding suggests that perhaps the medical recommendations regarding BMI, which are made from general studies around weight and health, should be adjusted for this age group. In an article also published in Nature by Jean Woo, from the Chinese University of Hong Kong, said benefits are also observed by other studies. “Still, these discoveries have been largely ignored by healthcare professionals, even though they have been reviewed in the US, Australia, Europe and Hong Kong,” Woo warns.
Felipe Casanueva, a professor at the University of Santiago de Compostela in Spain who was not a part of the investigation, considers it “interesting and well done,” but believes that “recommendations for a healthy life can’t be change based on a single study,” and “excess weight should be avoided at all ages.” However, he explains, with age, obesity issues change. “Sarcopenic obesity may develop, which happens when weight is maintained but body composition changes: fat increases and muscle decreases.” This makes studying fat and muscle percentages in patients vital and explains why, in addition to a good diet, exercise programs are so important for the elderly to preserve muscle mass. Other factors, like the effects of osteoporosis on the vertebrae, cause height loss with aging, explaining part of the increase in BMI in the group studied by the Chinese team.
The authors point out that recent data suggests certain risks factors for cardiovascular health, such as having high cholesterol or blood pressure, are related to better health and higher survival rates among older people, something that seems to be in line with their results.
Among the possible explanations for this paradox of obesity, Xiaoming’s team points out that being overweight may be a sign of a better nutritional status, which would compensate for the risks of weighing too much, and points out that an excess of fat may represent “a protective energy stock […] or the sequestration of toxins in fat to provide a survival advantage.” In addition, it’s important to highlight that starting at 60, average weight tends to decrease due to the loss of muscle mass, something that can explain health impairment.
The work published in Nature Aging concludes these and other similar results are suggesting it’s necessary to interpret BMI and how it relates to health while considering other factors like age, fat and muscle percentages and underlying medical conditions.