Weight Gain in Early Adulthood Linked to Higher Mortality Risk, Study Finds

A large observational study of Swedish adults has found that weight gain during early adulthood is associated with an increased risk of all-cause and cause-specific mortality later in life. The research, published in eClinicalMedicine, suggests the timing and pattern of weight gain may be significant factors in long-term health outcomes.

Study Overview and Methodology

The research analyzed data from the Obesity and Disease Development Sweden (ODDS) pooled cohort study, which included 258,269 men and 361,784 women. Unlike previous studies that used only two weight measurements, this analysis modeled continuous weight trajectories using repeated measurements across adulthood.

Key Age Points: Researchers examined weight changes between ages 17 (start of adulthood), 29 (end of young adulthood), and 60 (start of older adulthood).
Follow-up Period: The median follow-up was 23 years for men and 12 years for women.
Mortality Data: During the follow-up period, 86,673 men and 29,076 women died, with a median age at death of 77 years for men and 78 years for women.

Key Findings on Weight Gain and Mortality

The study reported a median weight change of 0.42 kg per year between ages 17 and 60, resulting in a median total gain of 18 kg for men and 17 kg for women.

All-cause mortality progressively increased among individuals who gained weight more rapidly before age 60, became obese as young adults, or gained considerable weight between ages 17 and 29.

The analysis identified several patterns:

Weight gain specifically between ages 17 and 29 showed a linear association with higher risk of all-cause, cardiovascular disease, and cancer mortality.
Late weight gain (after age 29) was generally more weakly associated with increased mortality rates.
The lowest mortality risk was observed in individuals with a modest weight gain of 0 to 0.25 kg per year.

Quantified Risk Increases:

With weight gain of 0.5 kg per year during ages 17-29, all-cause mortality increased by 18% among men and 16% among women.
Men who gained more weight between ages 17-29 had a 69% higher all-cause mortality risk compared to those who never became obese by age 60. The comparable risk increase for women was 71%.

Cause-Specific Mortality and Sex Differences

The strongest mortality associations were found with type 2 diabetes, hypertension, liver cancer in men, and uterine cancer.

Cardiovascular disease accounted for 37% of the excess deaths identified in the study.
Cancer mortality accounted for 31% of the excess deaths.

The study noted differences in weight gain patterns between sexes:

Men gained weight most rapidly in early adulthood.
Women showed stable weight gain rates between ages 17 and 29.
Early adulthood weight gain showed a stronger association with cancer mortality in men than in women.

Study Limitations and Research Context

The authors outlined several important limitations common to observational studies:

The study design prevents inference of causality.
Researchers could not distinguish between deliberate and inadvertent weight loss.
Important potential confounding factors, such as diet, physical activity, and comorbidities, were not fully captured.
The possibility of false positives or unmeasured confounding could not be ruled out, though a negative control analysis using brain cancer mortality showed no association, which the authors noted suggests against major spurious bias.

The researchers stated that the weight gain patterns observed in their Swedish study population were similar to those in typical Western populations. They also noted their findings differ from a previous American study on similar outcomes, a difference they attribute to variations in methodology, including baseline age and the number of weight measurements used.

Conclusions and Implications

The study's authors concluded that weight gain in early adulthood and becoming obese before age 30 are associated with higher all-cause and cardiovascular disease mortality risk later in life.

They indicated that the duration of obesity may be a more important factor than weight gain in late adulthood.

The findings, according to the researchers, highlight the potential need for early obesity prevention strategies. They suggested that future research should include more detailed measurements, such as changes in fat mass, muscle mass, and central adiposity, along with more comprehensive data on lifestyle and health confounders.