It has long been known that overweight and obesity increase the risk of several diseases, but when excess weight occurs can also play a significant role for health later in life, according to a new Swedish study.

Over 600,000 people are included in Lund University’s study, which closely examined how weight change from age 17 to 60 is linked to the risk of dying from various diseases. The results are clear—the greatest impact comes from increased weight early in adulthood.

– The clearest thing we see is that weight gain at a younger age is connected to a higher risk of premature death later in life, compared to people with lower weight gain, says Tanja Stocks, Associate Professor of Epidemiology at Lund University and one of the researchers behind the study, which is now published in eClinicalMedicine.

To participate in the study, it was required at least three weight measurements—for example, in early pregnancy, military enlistment, or as a participant in a research study. During the study period, 86,673 men and 29,076 women died.

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Individuals who gained weight more quickly during adulthood faced higher risk of dying from various obesity-related diseases, but also an increased risk of death from any cause. Those who developed obesity between ages 17 and 29 had a 70 percent higher risk of premature death compared to those who did not develop obesity before age 60.

– One possible explanation for why those who develop obesity early in life face higher risk is that the body is simply exposed for a longer time to the biological effects of overweight, says Huyen Le, doctoral student at Lund University and lead author of the study.

Clear Patterns

The pattern diverged in one case—cancer among women. One possible explanation is believed to be hormonal changes linked to menopause.

– There, the risk was about the same regardless of when the weight gain occurred. If long-term exposure to obesity were the decisive factor, earlier weight gain should mean higher risk. The fact that this is not the case suggests that other biological mechanisms may also play a role in cancer risk and survival among women, says Huyen Le.

According to Tanja Stocks, we should not focus too heavily on the exact risk figures, as they rarely become entirely accurate since, for example, they are influenced by environmental factors considered in the study and how well both risk factors and outcomes have been measured. She emphasizes, however, the importance of recognizing the patterns and stresses that the study sends an important message to policymakers about the need to prevent obesity.

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