People who lose weight to go from obese to overweight by midlife can halve their risk of death, finds study
Is weight loss between early adulthood and midlife associated with reduced risk of death later in life compared with persistent obesity? New research suggests that there is a link. Going from ‘obese’ in early adulthood to ‘overweight’ in midlife can halve the risk of dying prematurely, according to researchers from the Boston University School of Public Health (BUSPH). On the other hand, weight loss after midlife does not significantly reduce a person’s risk of death, reveals the nationally representative study of US adults.
According to the World Health Organization (WHO) and the National Institutes of Health (NIH), people are considered overweight if they have a body mass index (BMI) of 25 or higher and obese if their BMI is 30 and higher.The team estimates that 12.4% of early deaths in the US may be attributable to having a higher body mass index at any point between early- and mid-adulthood.
“The present study provides important new evidence on the benefit of maintaining a healthy weight across the life course,” says lead author Dr. Wubin Xie, a postdoctoral associate in global health at BUSPH.
The researchers used data from 1998 through 2015 for 24,205 participants from the National Health and Nutrition Examination Survey. The participants were 40-74 years old when they entered the study and the data included participants’ BMI at age 25, 10 years before they entered the study and when they entered the study. The researchers then analyzed the relationship between BMI change and the likelihood that a participant died over the course of the observed period, controlling for other factors such as participants’ sex, past and current smoking, and education level.
“Weight history was assessed by self-reported weight at age 25 years, at 10 years before baseline. Body mass index at each time was categorized as normal (18.5-24.9), overweight (25.0-29.9), and obese (30.0). Weight change patterns were assessed from age 25 years (early adulthood) to 10 years before baseline (midlife),” write authors in the study published in JAMA Network Open. The study participants were defined to be at midlife mainly between the ages of 37 and 55, but 44 on average, says the team which also includes experts from University of North Carolina Gillings School of Public Health, University of Pennsylvania, Harvard Medical School, and Harvard TH Chan School of Public Health.
The analysis reveals that study participants whose BMIs went from the “obese range” at age 25 down to the “overweight range” in midlife were 54% less likely to have died than participants whose BMIs stayed in the obese range. Instead, these participants with an obese to overweight trajectory had a risk of death closer to that of participants whose BMIs had been in the overweight range all along, the team explains. The authors did not find a similar reduction in the risk of death for participants who lost weight later in their lives. According to them, this may be because weight loss later in life is more likely to be tied to an aging person's worsening health.
The team estimates that 3.2% of deaths in the study could have been avoided if everyone with a BMI in the obese range at age 25 had been able to bring their BMIs down to the overweight range by midlife. Preventing weight gain from normal weight could prevent more than 12% of premature deaths, they add. However, weight loss was rare in the study population. Only 1.3% of the individuals who were overweight at age 25 years lost weight to a normal BMI 10 years before baseline, and 0.8% lost weight from obese to overweight, and 0.2% lost weight from obese to normal. The findings indicate an important opportunity to improve population health through primary and secondary prevention of obesity, particularly at younger ages, explains the study’s corresponding author Dr Andrew Stokes, assistant professor of global health at BUSPH.
“Compared with remaining obese, weight loss from an obese BMI in early adulthood to an overweight BMI in midlife was associated with more than a 50% reduction in the subsequent risk of early death. At the population level, we estimated that weight loss from obese to overweight would prevent more than 3% of premature deaths. An estimated 12.4% of early deaths could be avoided if the entire population with a BMI above normal weight instead had a normal BMI from age 25 years through midlife. Our findings support the importance of population-based approaches to preventing weight gain across the life course and a need for greater emphasis on treating obesity early in life,” says the research team.
While this study focused on preventing premature deaths, maintaining a healthy weight will also reduce the burden of many chronic diseases such as hypertension, diabetes, heart disease, and even cancer, suggests study co-author Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women's Hospital, and professor of medicine and Michael and Lee Bell Professor of Women's Health at Harvard Medical School.