Gaining weight from your mid-20s into middle age is associated with an increased risk of premature death, finds a study of US adults published by The BMJ today.
Weight loss at older ages (from middle to late adulthood) was also linked to higher risk. These findings highlight the importance of maintaining normal weight throughout adult life to reduce the risk of premature death, say the researchers.
Obesity in adults is known to be linked to higher risk of premature death. In the United States, 36% of men and 38% of women were obese in 2016, up from 11% of men and 14% of women in 1975. But little is known about the long term effects of weight change during adult life, especially from young to middle adulthood.
To explore this further, researchers based in China set out to investigate the association between weight changes across adulthood and mortality.
Their findings are based on data from the 1988-94 and 1999-2014 US National Health and Nutrition Examination Survey (NHANES) - a nationally representative annual survey that includes interviews, physical examinations, and blood samples, to gauge the health of US citizens.
Their analysis included 36,051 people aged 40 years or over with measured body weight and height at the start of the survey (baseline) and recalled weight at young adulthood (25 years old) and middle adulthood (average age 47 years).
Deaths from any cause and specifically from heart diseases were recorded for an average of 12 years, during which time there were 10,500 deaths.
After taking account of potentially influential factors, the researchers found that people who remained obese throughout adult life had the highest risk of mortality, while people who remained overweight throughout adult life had a very modest or no association with mortality.
Weight gain from young to middle adulthood was associated with increased risk of mortality, compared with participants who remained at normal weight. Weight loss over this period was not significantly related to mortality.
But as people got older, the association between weight gain and mortality weakened, whereas the association with weight loss from middle to late adulthood became stronger and significant.
No significant associations were found between various weight change patterns and cancer mortality.
This is an observational study, and as such, can't establish cause, and the researchers can't rule out the possibility that some of the observed risk was due to unmeasured factors.
But they say the results were based on a large, nationally representative sample, with high follow-up rate and detailed analysis of weight change patterns in different life periods.
As such, they conclude: "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."
They add: "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."
Evidence type: Observational