Excess weight in early adulthood linked to higher risk of premature death
Entering adulthood at a healthy weight could significantly reduce the risk of dying early from heart disease, cancer and respiratory illness, according to new international research.
A major study led by Oxford Population Health, based at the University of Oxford, in collaboration with researchers in China has found that body weight in early adulthood has a lasting impact on long-term health outcomes. The findings, based on data from around half a million adults in China, were published in Science Bulletin.
Most previous research on body mass index (BMI) and mortality has relied on measurements taken in middle or later life, when weight loss linked to illness can distort results. To avoid this, the research team examined BMI at around 25 years of age and tracked how this related to deaths from all causes and from specific diseases later in life.
The study analysed data from the China Kadoorie Biobank, which recruited participants from ten urban and rural regions across China at an average age of 52, with follow-up over around 12 years. Participants reported their weight at age 25, which was combined with their measured adult height to estimate BMI in early adulthood.
Key findings include:
Higher BMI at age 25 was linked to a higher overall risk of premature death, including deaths from cardiovascular disease, cancer and respiratory disease, with risk increasing steadily as BMI increased.
People who were living with obesity in early adulthood had an 85 per cent higher risk of premature death and death from cardiovascular disease compared with those who had a BMI in the healthy range.
The strongest link was seen with respiratory disease, where early adulthood obesity was associated with more than double the risk of death.
Higher BMI at 25 was linked to increased cancer mortality overall, but a lower risk of death from breast cancer among women.
Higher BMI in early adulthood was strongly associated with raised blood glucose levels later in life, though not with blood pressure once adult BMI was taken into account.
Importantly, the researchers found that these risks were independent of body weight later in life. This suggests that carrying excess weight in early adulthood may have long-term health effects that are not fully reversed even if weight is lost later on.
Many earlier studies have suggested a “J-shaped” relationship between BMI and mortality, with both low and high BMI linked to higher risk of early death. However, those studies often relied on BMI measured later in life, when underlying illness can lead to unintentional weight loss. By focusing on early adulthood, this study found little evidence that lower BMI levels were linked to increased mortality risk.
Commenting on the findings, Associate Professor Huaidong Du from Oxford Population Health said: “Our results suggest that the harmful effects of obesity begin early and can persist across the life course. While reducing obesity at any age is beneficial, maintaining a healthy weight from early adulthood appears to offer the greatest long-term protection.
“Although obesity was relatively uncommon in early adulthood in this population, the strength of the associations is concerning given that obesity rates among adolescents and young adults are rising worldwide.”
The researchers say further studies looking at blood biomarkers could help explain how excess weight in early adulthood increases the risk of conditions such as diabetes, breast cancer and premature death later in life.