Compared to having a normal weight at age 25 and at midlife, going from being nonobese to obese during those years was linked with an increased risk of premature death from heart disease, or all-causes, in later life, researchers report.
Remaining obese at all three life stages analyzed by researchers — early adulthood (age 25), middle adulthood (roughly age 47), and older adulthood (roughly age 57) — was associated with an even higher risk of premature death from these causes in later life (roughly age 57 to 69).
However, parodoxically, moving from being obese in midlife to nonobese in older adulthood was also associated with the same increased mortality risk, in this cohort of participants in a US national survey.
“The findings imply that maintaining normal weight across adulthood, especially preventing weight gain in early adulthood, is important for preventing premature deaths in later life,” write Chen Chen, Huazhong University of Science and Technology, Wuhan, China, and colleagues in a study published October 16 in BMJ.
“Young adulthood is a critical period when weight gain (mostly with body fat increase) is common,” senior author An Pan, PhD, a professor at Huazhong, told Medscape Medical News in an email.
“At the societal level”, the government should establish a non-obesogenic environment (such as food, housing options, social environments) “to make healthy choices easy, accessible, affordable, and even as a default choice.”
However, other experts advise against selectively interpreting the study findings.
And they caution against lumping the categories “overweight” and “obesity” together because — at least in this study — there were no deleterious associations with mortality with the overweight category. In fact, in some categories, being overweight was linked to a lower risk of premature death.
The researchers also acknowledge several study limitations — including that weight at age 25 and midlife was based on patient recall decades later, and the age ranges for midlife and older adulthood overlapped.
Nevertheless, given that people find it very difficult to go from being obese to nonobese (attained by only 1.4% of participants in this cohort), they stress that the takeaway message is that it is important to prevent [excess] weight gain in young adulthood.
Weight Change in Adulthood and Risk of Premature Death
A high body mass index (BMI) in adulthood is associated with a greater risk of premature death, Chen and colleagues write, but it is not clear how weight changes throughout adulthood affect this risk, they say, noting that prior scientific evidence on this topic “is not entirely consistent.”
To examine this, they identified 36,051 participants in the 1988–1994 and 1999–2014 US National Health and Examination Survey (NHANES).
The participants completed the survey and were weighed and measured when they were older adults (mean age 57, interquartile range 46 to 66 years; range 40 to 90 years).
At this baseline, they were asked to recall their weight at age 25 (young adulthood) and 10 years earlier (middle adulthood, mean age 47, interquartile range 36 to 56 years; range 30 to 80 years).
During this follow-up, 10,500 participants died.
After adjusting for multiple confounders, compared with participants who maintained a normal weight from age 25 to midlife, those who went from nonobese to obese during this period had a significantly increased risk of all-cause mortality and death from heart disease during follow-up (hazard ratio [HR], 1.22 and 1.49, respectively).
Being consistently obese was associated with even worse survival.
Specifically, being obese from age 25 to midlife, from age 25 to older adulthood, and from midlife to older adulthood, was associated with a 72%, 61%, and 20% increased risk of all-cause mortality in later life, respectively.
However, going from being nonobese in midlife to obese in older adulthood was not associated with significantly increased risk of premature mortality.
And being overweight had a very modest or null association with mortality across adulthood.
“Weight-Loss Story Is More Complicated”
Regarding the paradoxical findings on losing weight at an older age — going from being obese in midlife to nonobese in older adulthood (which was associated with a significantly increased risk of all-cause and cardiovascular mortality in later life [HR, 1.30 and 1.48, respectively]) — Pan said, “The story is more complicated.”
“We do not know whether those weight losses were intentional or unintentional,” he explained.
Or they may have been trying to lose weight and keep it off, but their weight may have been constantly fluctuating, or they may have chosen unhealthy ways to lose weight, which increased their risk of dying early.
More studies are needed to better understand these findings.
In contrast, several clinical trials, Pan noted, have shown “that weight loss through healthy lifestyle interventions (such as energy restriction, dietary changes) for most people, and bariatric surgery for certain [people with] morbid obesity, are beneficial for health outcomes and long-term longevity.”
“Therefore, I do think we should still recommend people to lose weight if they are overweight or obese,” he said, “but it is much better to be monitored and in scientifically proven weight-loss programs.”
Important Study Limitations
Commenting on the study, Andrew W. Brown, PhD, assistant professor at Indiana University School of Public Health in Bloomington and a spokesperson for the Obesity Society, told Medscape Medical News that “the mixed results, in which some analyses showed beneficial and detrimental associations with both weight gain and loss, highlight that the relationship between weight and mortality is complex, and between gaining or losing weight and mortality even more so.”
Keisuke Ejima, PhD, assistant research scientist at IU School of Public Health who is studying life-course mortality, concurred with Pan, adding that “these results need to be considered in the context of reasons for weight gain or loss (eg, disease, stress, disorders, psychosocial factors, social determinants, medication use), as well as all other analyses that have looked at the relationship between weight and mortality.”
Brown also stressed that it is important to note that there were likely weight recall errors and the age categories were blurred.
“We know there are issues with people self-reporting what they weigh today, let alone what they remember years, sometimes decades, into the past,” he said.
And the age categories were fuzzy, since in middle adulthood (ages 30 to 80), 25% of the participants were older than 56, and in older adulthood (ages 40 to 90), 25% of the participants were younger than 45.
“Overweight Is Not the Same as Obesity”
“The authors did not see deleterious associations with mortality with the overweight category,” Brown pointed out.
The investigators report “stable overweight was not significantly associated with mortality risk except for an inverse association in the 10-year period before baseline,” and “the overweight to normal pattern was consistently associated with higher mortality risk in the three time periods.” In addition, say the authors, “the normal to overweight pattern was associated with lower mortality risk from age 25 years to baseline…and in the 10-year period before baseline.”
Thus, “overweight in [all] these cases was associated with lower mortality,” Brown summarized.
“We cannot selectively interpret the results,” he maintains. “If we are okay concluding that ‘stable obese’ (as they call it) represents consistent increased risk of mortality, then we also need to highlight that ‘stable overweight‘ [does] not.”
“We…cannot ignore that modest weight gains were not associated with increased mortality,” according to Brown.
All agree that further studies are needed.
“Many Things Could Be Done”
In the meantime, Pan said “there are many things that could be done” to combat obesity and lower the risk of premature death, and these are discussed in a comprehensive Lancet Commission report published in January that he coauthored, titled “The Global Syndemic of Obesity, Undernutrition, and Climate Change.”
The report authors urge “a radical rethink of business models, food systems, civil society involvement, and national and international governance to address the global syndemic [synergistic interaction of health problems] of obesity, undernutrition, and climate change,” stressing their belief that “the current approach to obesity prevention is failing despite many piecemeal efforts, recommendations and calls to action.”
The current study was funded by grants from the National Key Research and Development Program of China, the China Postdoctoral Science Foundation, and the International Postdoctoral Exchange Fellowship of the China Postdoctoral Council. The study authors have disclosed no relevant financial relationships.
BMJ. Published October 16, 2019. Full text