A research showed that people whose weight decreased from the indication of obesity to the indication of overweight between early adulthood and midlife were at less the risk of death during the follow-up.
The World Health Organization ( WHO ) reports that as of 1975, the global prevalence of obesity has nearly tripled. More than 650 million people experienced obesity in 2016.
According to the Centers for Disease Control and Prevention ( CDC), the prevalence of obesity among adults in the United States rose from 30.5 per cent to 42.4 per cent of the population between 1999 and 2018.
Obesity is associated with an elevated risk of heart disease , stroke , type 2 diabetes and other types of cancer, making it a significant cause of premature preventive death.
However, estimates of the number of deaths attributable to obesity differ widely, due to the complex relationships between body weight and factors such as age, smoking, diet , and physical activity.
Furthermore, scientists are still unsure if bearing excess weight at young adulthood induces detrimental physiological changes which can not be reversed by subsequent weight loss.
A team led by researchers at the Boston University School of Public Health, Massachusetts, set out to find out if weight loss after early adulthood obesity is associated with a later-life reduction in mortality risk.
The scientists published their results recently in the JAMA Network Open journal.
Healthy weight
A measure called the body mass index ( BMI) is sometimes used by doctors to assess if a person has a healthy weight. In order to measure this, the doctor divides the weight of the individual into kilograms by their height into squared metres.
Experts describe a balanced BMI as 18.5–24.9, one for overweight as 25.0–29.9, and one for obesity as 30 or greater.
Data from 24,205 U.S. citizens who were part of the National Health and Nutrition Review Survey ( NHANES) were examined by researchers behind this study.
As part of that study , scientists registered participants’ weights when they were between 40 and 74 years of age. They also asked the participants how heavy they were 10 years earlier, identified by the researchers as midlife, and at the age of 25, known as early adulthood.
The team behind the current study looked at improvements in BMI from early adulthood to midlife and their effect on mortality, assessed during the follow-up period of NHANES. They then took into account other factors influencing mortality risk, such as gender, past and current smoking, and the level of education.
Participants had 5,846 deaths over a mean follow-up period of 10.7 years.
The team found that going from a BMI suggesting obese in young adulthood to one suggesting midlife overweight was associated with a 54% decrease in mortality risk compared to maintaining an obese BMI over the same period.
People who moved from obese to overweight between young adulthood and midlife also had almost the same risk of mortality as those who only had overweight during this period.
Taken together , the findings suggest that you can reverse the adverse effects of obesity.
Preventing early death
Scientists estimate that 3.2 per cent of all early deaths in the sample would have been avoided if individuals with BMIs suggesting obesity had decreased this indicator to fall by midlife within the range of overweight.
Furthermore, they conclude that 12.4 percent of all early deaths could have been avoided if everyone with a BMI suggesting overweight or obese had decreased it by middle age to fall into the safe range.
“The results indicate a significant opportunity to improve the health of the population through primary and secondary prevention of obesity , especially at younger ages,” says senior study author Prof. Andrew Stokes.
Another author of the research, Dr JoAnn Manson, head of preventive medicine at Brigham and Women’s Hospital in Boston, refers to the link between obesity and a number of chronic illnesses:
“Although this study focused on preventing premature deaths, maintaining a healthy weight will also reduce the burden of many chronic diseases like hypertension, diabetes , heart disease and even cancer,” she says.
However, the study found that weight loss among the participants was uncommon indicating the public health challenge presented by overweight and obesity.
Just 1.3 percent of individuals with BMIs in the 25-year-old overweight category had a healthy BMI 10 years prior to the NHANES interview, while by this measure 0.8 percent went from obese to overweight and 0.2 percent went from obese to a healthy BMI.
And while weight loss in early adulthood was associated with a significant reduction in mortality risk, the same was not true for those who later lost weight in life.
The authors suggest this is because weight loss can result from declining health later in life, rather than adopting a more balanced lifestyle.
They write:
“The discrepancy likely reflects the different nature of weight loss at an earlier versus later life course. Weight loss at an older age is often unintentional, associated with underlying health conditions, and/or age-related loss of muscle mass, whereas weight loss earlier in life tends to capture changes in fat mass and is less likely to be affected by the onset of chronic diseases.”
Overweight and obesity threats
The transition from a healthy or overweight BMI in young adulthood to a BMI in the midlife obesity range was correlated with increases of 32 percent and 47 percent respectively in mortality risks compared to remaining in the safe category.
However, the researchers note that moving from a balanced BMI to an overweight BMI, relative to maintaining a healthy weight, was not correlated with a substantial improvement in mortality risk.
This is consistent with other research, showing that being in the range of overweight doesn’t automatically shorten lives, though this remains controversial.
Rounding off their report, the scientists explain that their study had several limitations.
To measure the weight shift between early adulthood and midlife, scientists had focused 10 and 25 years earlier on the participants’ recollections of their weights. Furthermore, early adulthood the team did not compensate for physical activity or diet.
Finally, there was a small percentage of participants who lost weight, which the scientists believe limits the accuracy of their results.
