(Courtesy of Lv Yuebin)
After the age of 80, what should be the best body mass index (BMI) for the human body?
A 20-year prospective cohort study by Chinese scholars showed that overweight or mild obesity in the elderly over the age of 80 may be the most beneficial to health and longevity.
This phenomenon has been dubbed the “obesity paradox” by researchers, and the results of the study were published online on April 25 by Nature Aging. Lv Yuebin, associate researcher of the Institute of Environment and Health-related Product Safety of the Chinese Center for Disease Control and Prevention (hereinafter referred to as the Institute of Environment), and Shi Xiaoming, a researcher, are the first authors and corresponding authors of the paper.
Older adults who are overweight and mildly obese may live longer
Contemporary people almost talk about “fat” discoloration, and people who are considered “fat” often face discrimination. In the health sector, overweight (24≤ BMI<28 kg/m2) or obesity (BMI≥28 kg/m2) are also often closely associated with chronic disease and death risk. Obesity has even been called a worldwide epidemic.
The “obesity paradox” of the elderly, contrary to previous beliefs, may surprise you, as reported in a study published by Shi Xiaoming’s team in jama network open and in the Journal of the American Medical Directors Association.
Based on the follow-up data analysis of more than 27,000 elderly people aged 80 and above in China from 1998 to 2018, Shi Xiaoming’s team found that compared with the elderly with normal BMI (18.5 to 23.9), the risk of death and daily life self-care ability (ADL) disability increased by about 30%, while the corresponding risk of overweight and mild obesity (24.0 to 31.9) decreased by about 20%.
Since its discovery, however, there has been controversy over the legitimacy of the “obesity paradox.”
The team’s new article published in Nature-Aging confirms and explains the previous research results of the “obesity paradox” based on the risk of death based on the risk of death by cause of death, different body composition volume indicators, and weight changes.
Explaining the “Obesity Paradox”
After adjusting the confounding factors, the study found that BMI was associated with the risk of cardiovascular disease death, the risk of non-cardiovascular disease death, and the risk of all-cause death, and the corresponding risk tangent points were in the range of overweight and mild obesity. In particular, overweight and obesity no longer increase the risk of cardiovascular disease death in the elderly, while reducing the risk of non-cardiovascular disease death.
A similar association was found in waist circumference: higher waist circumference was protective of non-cardiovascular disease and all-cause mortality. It may be that fat is providing protective energy reserves for the elderly.
Lü Yuebin told China Science News that according to China’s current BMI-based standards, 20% of the elderly over 80 years old are overweight, and about half are low weight, “many low weight is actually malnutrition.”
The article also analyzes that the reason for the association of “inverted J-type” may be that low fat capacity increases the risk of non-cardiovascular death, and maintaining appropriate muscle volume can reduce the risk of death from non-cardiovascular disease.
Therefore, it is clear that older adults with different BMI should have individualized weight management strategies. The article recommends that medical personnel and public health practitioners should pay more attention to nutritional support and prevention of weight loss in the elderly, as well as maintaining the appropriate weight and body composition of the elderly.
Expect more accurate weight management guidelines
The findings further found that for low-weight people, weight gain reduced the risk of death; for overweight and obese people, weight gain significantly increased the risk of cardiovascular disease death; and for normal-weight people, the risk of death from maintaining a stable weight was minimal.
A commentary published at the same time in Nature-Aging argues that this conclusion challenges the application of current public health guidelines based on BMI criteria for determining overweight and obesity in the elderly.
In fact, the data of the seventh census in 2020 shows that the number of elderly people in China has reached 35.8 million, which is a huge group that needs special attention to health, and its population size exceeds the total population of most countries. International and national weight management guidelines are based primarily on evidence of the general adult population and may indeed not apply to the elderly.
The good news is that this phenomenon has received more and more attention from peers in the industry, according to Lu Yuebin, the Chinese Nutrition Society in 2021 on the “China Elderly Suitable Weight and Weight Management Guidelines” officially approved, the guide is expected to be released within this year.
For the suggestions of a healthy lifestyle, Shi Xiaoming told this reporter that the elderly should first pay attention to dietary diversification, eat as many foods as possible, do not make it up; secondly, pay attention to eating more protein-rich foods, including meat (lean), eggs, beans, fish and seafood, etc.; In addition, more participation in leisure activities, active integration into society, beneficial to the elderly to maintain physical and mental health. (Source: China Science Daily Zhang Nan)
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