People who gain weight in their 20s, 30s, and 40s are at an increased risk of premature death, according to a study of US adults published in The BMJ yesterday.
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Researchers at Huazhong University of Science and Technology found that people who became obese between the ages of 25 and 47 were at a 22% increased risk of premature death from any cause and a 49% increased risk of dying from heart disease.
The study also found that gaining weight between middle age and old age increased the risk of dying young, but that the same was also true for people who lost weight and went from obese to a healthy weight during this time.
Study author An Pen and colleagues say the findings underscore the importance of maintaining a normal weight as an adult to lower the risk of premature death.
Little is known about the long-term effects of weight change during adulthood
Obesity during adulthood is already known to be associated with an increased risk for premature death. In 2016, 36% of men and 38% of women in the United States were obese, compared with 11% of men and 14% of women in the year 1975.
However, little is known about the effects that weight change during adult life has in the long term, especially weight change between young and middle adulthood.
To investigate, Pan and colleagues explored associations between weight changes during adulthood and mortality.
They conducted a prospective cohort study using data from the US National Health and Nutrition Examination Survey (NHANES) 1988-94 and 1999-2014. The survey is a nationally representative annual survey designed to gauge the health of US citizens and includes data from interviews, physical examinations, and blood samples.
The findings were based on data available for 36,051 people aged 40 years or older at baseline who had their body weight and height measured. They recalled what their weight was at 25 years old and at middle adulthood (10 years before baseline [average age 47]).
Deaths from any cause and specifically from heart disease were recorded over a mean follow-up period of 12.3 years.
Staying obese throughout adulthood carries the biggest risk
The authors report that overall, there were 10,500 deaths during the follow-up period.
After adjusting for potential confounders, the team found that people who stayed obese throughout adult life were at the greatest risk of all-cause mortality, compared with people who sustained a normal weight throughout adulthood. For people who stayed obese between young and middle adulthood, the increase in risk was 72%; for young to late adulthood the increase was 61% and from mid- to late adulthood, the increase was 20%.
Gaining weight between young and middle adulthood was associated with an increased risk of dying, while losing weight during this time was not associated with an increased risk.
Compared with people who retained a normal weight, those who went from non-obese to obese between young and middle adulthood were at a 22% increased risk for all-cause mortality and a 49% increased risk for heart disease mortality.
By contrast, no such increases in mortality risk were observed for people who lost weight and went from being obese to a healthy weight over the same period.
However, as people grew older, the association between weight gain and mortality weakened, whereas it became stronger for people who lost weight.
Those who went from being obese to a healthy weight between middle age and late adulthood were at a 30% increased risk of all-cause mortality and a 48% increased risk of heart disease mortality.
The authors acknowledge that the research was observational and therefore cannot reliably determine the causes of the associations. However, the findings were based on a large, nationally representative sample with a long follow-up period and detailed analysis of weight changes across different life stages, they say.
The author's write:
Stable obesity across adulthood, weight gain from young to middle adulthood, and weight loss from middle to late adulthood were associated with increased risks of mortality. The results highlight the importance of maintaining normal weight across adulthood, especially preventing weight gain in early adulthood, for preventing premature deaths in later life."
The message 'couldn't be clearer' but 'few people appear to have listened'
Tam Fry, spokesman for the National Obesity Forum, says: “The message to maintain a healthy weight throughout life couldn’t be clearer.”
He referred to the well-respected Foresight Report that first shocked the UK twelve years ago by predicting that being fat could knock 13 years off your life: “Given the continuing rise of obesity-related hospital admissions, few people appear to have listened.”
Pan and colleagues say further research is needed to uncover the mechanisms underlying the association between weight change across adulthood and mortality, particularly the association between changes in body composition and mortality.
“In addition, as weight loss is less achievable (only 1.4% participants changed from the obese to the non-obese category from young to late adulthood), our results suggest that prevention of weight gain might be more important,” they conclude.
Chen, C. et al. (2019). Weight change across adulthood in relation to all cause and cause specific mortality: prospective cohort study. BMJ. DOI: 10.1136/bmj.l5584