Weight gain during a person’s lifetime can have a significant impact on their health decades later. A large-scale study conducted by Sweden’s Lund University of more than 600,000 people looked at how weight change between the ages of 17 and 60 is associated with the risk of death from various diseases. The findings show a clear trend that weight gain in early adulthood has the strongest impact on long-term health.
It has long been known that obesity increases the risk of many diseases. Rather than focusing solely on obesity at one point in time, this study looked at how changes in weight across adulthood affect health outcomes.
“The most consistent finding is that gaining weight at a young age is associated with a higher risk of premature death later in life than those who gain less weight,” said Tanja Stocks, associate professor of epidemiology at Lund University. She is one of the researchers behind this study, which is currently e-clinical medicine.
The study tracked more than 600,000 people using data from multiple records. Participants were only included if their weight was measured at least three times, including during early pregnancy, during military service, and when participating in a research study. During the study period, 86,673 men and 29,076 women died.
Accelerated weight gain leads to increased mortality
Researchers tracked how weight changed between ages 17 and 60 and compared those patterns to the risk of death from all causes and obesity-related diseases (see fact box below). On average, both men and women gained about 0.4 kg per year.
The analysis showed that people who gained weight faster in adulthood had a higher risk of dying from obesity-related conditions. People who became obese between the ages of 17 and 29 had an approximately 70 percent higher risk of premature death than those who did not become obese before age 60. Onset of obesity was defined as when BMI, a measure based on weight and height (kg/m2), first reached 30 or higher.
“One possible reason why people who develop obesity early on are at greater risk is that they are exposed to the biological effects of excess weight for a longer period of time,” said Huen Le, a doctoral student at Lund University and lead author of the study.
Exceptions to women’s cancer risk
One notable exception appeared in the results. For women with cancer, the timing of weight gain does not seem to change the level of risk.
“Regardless of when the weight gain occurred, the risk was about the same. If long-term exposure to obesity is the underlying risk factor, early 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 women’s cancer risk and survival,” says Huyen Le.
One possible explanation could be the hormonal changes associated with menopause.
“If the findings for women reflect what happens during menopause, then the question becomes chicken and egg. Hormonal changes may affect weight and the age and time period at which those changes occur, and weight simply reflects what’s going on inside the body.”
Reliable data supports our findings
The main strength of this study was the repeated measurements of body weight over many years. This allowed researchers to more accurately estimate long-term weight changes. Much of the early research was based on people recalling their past weights, which can be unreliable.
“The majority of weight measurements in this study were performed by staff, such as in medical settings. The predominance of objectively measured weight in our study contributes to more reliable and robust results,” says Tanja Stocks.
Understand increased risk
Population-level increases in risk can be difficult to interpret. For example, a 70% increase in risk means that if 10 out of 1,000 people in a group die during a given period, about 17 out of 1,000 people in that group will die from early obesity.
“But we shouldn’t get too hung up on exact risk figures, as they are rarely completely accurate, as they are influenced by, for example, the factors considered in the study and the precision with which both risk factors and outcomes were measured. However, it is important to recognize patterns, and this study sends an important message to decision-makers and politicians about the importance of obesity prevention,” says Tanja Stocks.
Role of “obesity society”
Many experts describe today’s environment as an “obesity society,” where our daily environment makes it difficult to maintain healthy habits and makes it easier to gain weight.
“It is up to policy makers to implement interventions that are known to be effective in combating obesity. This study provides further evidence that such interventions are likely to have a positive impact on people’s health.”
Fact: Obesity-related diseases
Obesity is associated with increased risk of several diseases. The most important ones are:
- Cardiovascular disease (most diseases such as heart attacks and strokes)
- type 2 diabetes
- high blood pressure
- Fatty liver disease (non-alcohol related)
- Some types of cancer (e.g., colon cancer, liver cancer, kidney cancer, uterine cancer, postmenopausal breast cancer, etc.)
Research overview
- Weight information was collected at least three times between ages 17 and 60
- Follow-up: Average 23 years for men and 12 years for women
- Number of participants: 620,000 people
Main results
- Greater weight gain increases risk of premature death
- Early-onset obesity (ages 17-29) was associated with approximately 70% higher overall mortality compared to those who did not become obese.
- An annual weight gain of 0.4 kg between the ages of 17 and 30, equivalent to a total weight gain of 6.5 kg between the ages of 17 and 30, was associated with an approximately 17% higher risk of premature death compared to those whose weight remained stable.
- This association applied to early death from all causes combined. The same pattern was observed separately for:
- Cardiovascular disease including various forms
- Cancer, especially obesity-related cancers
- Other causes related to obesity
- The risk increased further when weight gain and the onset of obesity occurred during young adulthood. One exception was cancer mortality in women, where weight gain at different ages showed a similar association.
