Weight gained in your 20s may matter more than later in life, with new evidence showing that early adult weight trajectories could shape your risk of dying from heart disease, cancer, and other chronic conditions decades later.
Study: Weight trajectories and obesity onset between 17 and 60 years of age, and cause-specific mortality: the Obesity and Disease Development Sweden (ODDS) pooled cohort study. Image credit: Flotsam/Shutterstock.com
A study in eClinicalMedicine suggests that weight gain in adulthood, especially before the age of 30 years, was associated with a higher risk of premature death.
Midlife weight change linked to major mortality risks
Existing evidence suggests that weight gain or a change in body mass index (BMI) in midlife (40–65) is associated with higher all-cause, cardiovascular, and cancer mortality. In prior research, cause-specific mortality analyses were based on single-point weight measurements, ignoring the potential for weight changes over time.
Previous analyses of cause-specific mortality associations with weight change have used only two points in adulthood, which cannot capture nonlinear or lifetime weight change.
Sex- and age-dependent differences
Men and women gain weight differently. In women, the rate of weight gain is stable between 17 and 29 years of age. Conversely, most weight gain in men occurs in early adulthood.
Age-specific weight changes also mirror changes in body composition. In early adulthood, most of the gained weight involves increased fat and muscle mass. Conversely, in later life, weight gain is due mostly to increased fat mass.
Repeated measurements used to model lifelong weight trajectories
The current study examines associations between longitudinal trends in weight and mortality. The authors modeled continuous weight trajectories across adulthood using repeated measurements instead of fixed time points. They highlighted key ages: 17 (the start of adulthood), 29 (the end of young adulthood), and 60 (the start of older adulthood). In addition, it attempts to distinguish the effects of weight gain in earlier adulthood versus midlife on mortality risk.
The data for this study were derived from ODDS, including 258,269 men and 361,784 women. The median follow-up was 23 years in men and 12 years in women. Over this period, 86,673 men and 29,076 women died. The median age of death was 77 years in men and 78 years in women.
Median weight gain was similar between sexes
The median weight change was 0.42 kg/year between 17 and 60 years, with a median total weight of 18 kg in men and 17 kg in women. Men put on weight most rapidly in early adulthood, while the proportion of obese individuals increased with age.
Weight gain linked to higher mortality risk
All-cause mortality progressively increased among those who gained weight more rapidly before 60 years; became obese as young adults; or gained considerable weight early (17–29 years). The association was stronger when respiratory disease and lung cancer were excluded from the analysis.
These combined exposure patterns were also associated with progressively increased cause-specific mortality in 13 of 23 conditions in men and 12 of 19 in women, although not all causes showed significant associations.
The strongest links were with mortality from type 2 diabetes mellitus (T2 DM), hypertension, liver cancer in men, and uterine cancer. Cardiovascular disease (CVD) accounted for 37 % of excess deaths.
Obesity onset in early adult life
The risk of all-cause mortality was 69 % higher among men who gained more weight by 17–29 years, compared to those who never became obese by 60 years. Among women, this risk was 71 % higher.
Early weight gain linked to excess risk
Between 17 and 29 years, weight gain was linearly associated with higher all-cause, CVD, and cancer mortality risk. With a gain of 0.5 kg/year over this period, all-cause mortality increased by 18 % among men and 16 % among women.
Late weight gain was generally more weakly associated with increased all-cause and most cause-specific mortality rates. Overall, the lowest mortality risk was observed within a narrow range of modest weight gain (0–0.25 kg/year), suggesting a J-shaped association rather than a strict threshold after 30 years.
Weight gain and cancer mortality
Cancer mortality accounted for 31 % of deaths. The strongest association with cancer mortality in men was with early adulthood weight gain. In women, cancer risk increased with weight gain across age groups. However, effect sizes were broadly similar across age groups in the main analysis, and the pattern became more similar to that observed in men when weight changes were expressed as 1 standard deviation per year rather than 0.5 kg/year.
The rate of weight gain is associated with a higher risk
Individuals who gained weight most rapidly had a 40 % higher risk of all-cause mortality compared to those with the slowest rate of weight change. This differs markedly from an American study exploring similar outcomes. The authors attribute this to differences in baseline age, the use of recall to establish the age at 25, and the use of only two weight measurements, introducing the risk of measurement error.
A negative control analysis was performed using brain cancer to test for spurious associations. This did not show an association and therefore did not suggest major spurious bias in the observed results.
Strengths and limitations
The study had a large sample size with multiple weight measurements across adult life. The findings were largely weighted by two large nationally representative cohorts. Registry data provided high-quality register-based ascertainment of the cause of death. The negative control analysis supported the robustness of the findings against major bias, though residual confounding cannot be fully excluded.
However, it has some limitations. The authors could not distinguish deliberate from inadvertent weight loss. Important confounders such as diet, physical activity, and comorbidities were not fully captured, and unmeasured confounding is likely, though it probably would not fully explain the observations. False positives could not be ruled out, and causality cannot be inferred from these observational findings.
Clinical implications
The weight gain patterns observed here were similar to those in typical Western populations, suggesting that the findings are generalizable.
These findings suggest that weight gain in adult life, especially among young adults, and becoming obese before the age of 30 years, were associated with higher all-cause and CVD mortality risk. The duration of obesity may be more important than late adulthood weight gain, as suggested by the observed associations, indicating the need for early obesity prevention strategies.
Future research should include changes in fat mass, muscle mass, and central adiposity, as well as more detailed information on confounding factors.
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