Gaining weight from your mid-20s into middle age is associated with an increased risk of premature death, warn researchers.
According to the study published in the BMJ journal, weight loss at older ages (from the middle to late adulthood) was also linked to higher risk.
"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," said study researchers from China.
For the study, researchers based in China set out to investigate the association between weight changes across adulthood and mortality.
Their findings were 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 the 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 an 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 the middle to late adulthood became stronger and significant.