Early Adulthood Obesity Significantly Increases Risk of Premature Death

Recent research indicates that gaining weight during early adulthood can lead to significant lifelong health consequences, including a higher risk of premature death. Two separate large-scale studies highlight the long-term impact of early-onset obesity and excess body mass index (BMI) on the development of chronic diseases.

A study from Lund University in Sweden, published in eClinicalMedicine and reported on April 11, 2026, examined weight changes in more than 600,000 individuals between the ages of 17 and 60. The researchers found that gaining weight earlier in adulthood has the strongest impact on long-term health outcomes.

According to the Lund University findings, early adulthood obesity significantly increases the risk of premature death, particularly from major diseases such as diabetes and heart disease. The research suggests that the damage to the body increases the longer a person carries excess weight.

The Impact of BMI at Age 25

Parallel research conducted by Oxford Population Health and institutions in China, published in Science Bulletin and reported on February 27, 2026, focused specifically on BMI at age 25. This study analyzed data from approximately half a million Chinese adults recruited through the China Kadoorie Biobank (CKB).

The CKB study followed participants for an average of 12 years, using self-reported weight at age 25 and measured height at the start of the study to calculate early adulthood BMI. The findings demonstrated that a higher BMI at age 25 is associated with a steadily increasing risk of death overall and from specific causes.

The research identified several key risks associated with excess weight in early adulthood:

• Individuals who were obese during early adulthood, defined as having a BMI of 28 kg/m2 at age 25, faced an 85% higher risk of premature death compared to those with a BMI between 18 and 24.9 kg/m2.
• There was a significantly higher risk of death from cardiovascular disease.
• There was an increased risk of premature mortality due to respiratory disease, with some findings suggesting a more than doubling of the risk.
• Higher early adulthood BMI was linked to an increased risk of death from cancer.

Addressing Reverse Causality in Health Research

The researchers at Oxford Population Health noted that much of the existing evidence linking BMI to mortality relies on measurements taken during middle or later adulthood. This often leads to reverse causality, where an existing illness causes weight loss, which can mistakenly suggest that a low BMI is associated with higher mortality.

By focusing on BMI at age 25, the study was able to isolate the effects of early adult adiposity from health changes that occur later in life, providing a clearer picture of how early weight shapes long-term outcomes.

Gender Differences and Biological Factors

While the general trend shows a strong link between early weight gain and premature death, the Lund University study noted a specific exception regarding cancer risk in women. The researchers found that cancer risk in women did not follow the same pattern as other health outcomes, suggesting that other biological factors may be influencing these results.

Tanja Stocks, Associate Professor of Epidemiology at Lund University, noted the consistency of the findings regarding the timing of weight gain.

The most consistent finding is that weight gain at a younger age is linked to a higher risk of premature death later in life, compared with people who gain less weight,

Tanja Stocks, Associate Professor of Epidemiology at Lund University

The combined evidence from these studies suggests that maintaining a healthy body weight from early adulthood is critical for reducing the lifetime burden of chronic diseases and increasing overall longevity.