Early weight gain is linked to lifelong health consequences

Obesity has long been known to increase the risk of many diseases. Instead of focusing only on obesity at a single point in time, this research looked at how weight changes throughout adulthood influence health outcomes.

“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,” says Tanja Stocks, Associate Professor of Epidemiology at Lund University. She is one of the researchers behind the study, which has now been published in eClinicalMedicine.

The study followed over 600,000 people using data from multiple records. Participants were included only if their weight had been measured at least three times, such as during early pregnancy, military conscription, or participation in research studies. Over the study period, 86,673 men and 29,076 women died.

Faster Weight Gain Linked to Higher Mortality

Researchers tracked how body weight changed between ages 17 and 60 and compared those patterns with the risk of death from all causes and from obesity-related diseases (see fact box below). On average, both men and women gained about 0.4 kg per year.

The analysis showed that individuals who gained weight more quickly during adulthood faced a higher risk of dying from conditions linked to obesity. Those who developed obesity between ages 17 and 29 had about a 70 percent higher risk of premature death compared with people who did not become obese before age 60. Obesity onset was defined as the first time a person’s body mass index, a measure based on weight and height (kg/m²), reached 30 or higher.

“One possible explanation for why people with early obesity onset are at greater risk is their longer period exposed to the biological effects of excess weight,” says Huyen Le, doctoral student at Lund University and first author of the study.

Exception Seen in Women’s Cancer Risk

One notable exception appeared in the results. For cancer in women, the timing of weight gain did not seem to change the level of risk.

“The risk was roughly the same regardless of when the weight gain occurred. If long-term exposure to obesity were the underlying risk factor, earlier weight gain should imply a 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 in women,” says Huyen Le.

One possible explanation could be hormonal changes associated with menopause.

“If our findings among women reflect what happens during menopause, the question is which came first: the chicken or the egg? It may be that hormonal changes affect weight and the age and duration over which these changes occur — and that weight simply reflects what’s happening in the body.”

Reliable Data Strengthens Findings

A key strength of the study is the use of repeated weight measurements over many years. This allowed researchers to estimate long-term weight changes with greater accuracy. Many earlier studies rely on people recalling their past weight, which can be less reliable.

“The majority of weight measurements in this study were, instead, taken by staff, for example in healthcare settings. The predominance of objectively measured weights in our study contributes to more reliable and robust results,” says Tanja Stocks.

Understanding the Risk Increase

Population-level risk increases can be difficult to interpret. For instance, a 70 percent increase in risk means that if 10 out of 1,000 people in one group die during a certain period, about 17 out of 1,000 would die in the group with early obesity.

“But we shouldn’t get too hung up on exact risk figures. They are rarely entirely accurate, as they are influenced, for example, by the factors taken into account in the study and the accuracy with which both risk factors and outcomes have been measured. However, it’s important to recognize the patterns, and this study sends an important message to decision-makers and politicians regarding the importance of preventing obesity,” says Tanja Stocks.

The Role of an “Obesogenic Society”

Many experts describe today’s environment as an “obesogenic society,” where everyday conditions make it harder to maintain healthy habits and easier to gain weight.

“It’s up to policymakers to implement measures that we know are effective in combating obesity. This study provides further evidence that such measures are likely to have a positive impact on people’s health.”

Facts: Obesity-Related Diseases

Obesity is linked to an increased risk of several diseases. Some of the most important are:

• Cardiovascular disease (most forms, e.g. heart attack and stroke)
• Type 2 diabetes
• High blood pressure
• Fatty liver disease (non-alcohol-related)
• Several types of cancer (e.g. cancer of the colon, liver, kidney, uterus and breast cancer afterfollowing menopause)

The Study in Brief

• Weight information was collected at least three times between 17 and 60 years of age
• Follow-up: on average 23 years for men and 12 years for women
• Participants: 620,000 people

Key Results

• The greater the weight gain, the higher the risk of premature death
• Early-onset obesity (17-29 years of age) was linked to approximately 70 percent higher overall mortality compared with those who did not develop obesity
• A weight gain of 0.4 kg per year between ages 17 and 30, equivalent to a total weight gain of 6.5 kg between these ages of 17 and 30, was associated with an approximately 17 percent higher risk of premature death compared with those whose weight remained stable
• The associations applied to premature death from all causes combined. The same pattern was also observed separately for:
  • cardiovascular disease, including its various forms
  • cancer, particularly obesity-related cancer
  • other causes linked to obesity
• The risks increased further when weight gain and the onset of obesity occurred in young adulthood. One exception was mortality from cancer in women, where weight gain at different ages showed a similar association.