Three distinct clusters of body-shape change were identified over 2 years in Korean adults—Stable, Adiposity-Increasing, and Adiposity-Decreasing—with changes in body fat mass and skeletal muscle mass showing strong associations with cluster assignment, while worsening sleep quality and declining physical activity were significantly associated with the Adiposity-Increasing cluster.
Key Findings
Results
K-means cluster analysis identified three distinct clusters of body-shape change over 2 years: Stable (48.0%), Adiposity-Increasing (31.0%), and Adiposity-Decreasing (21.0%).
Clustering was applied to 1,404 participants from the Korean Medicine Daejeon Citizen Cohort.
Six body-shape indicators were used: 2-year changes in BMI, waist circumference, hip circumference, waist-to-hip ratio, waist-to-height ratio, and body weight.
Nearly half of participants remained in the Stable cluster, while roughly one-third experienced increasing adiposity and one-fifth experienced decreasing adiposity.
Results
Baseline body fat mass was significantly associated with cluster membership.
Baseline body fat mass was compared across the three clusters and showed statistically significant differences.
Cluster membership differences at baseline were specifically linked to body fat mass rather than other body composition or shape indicators.
Multinomial logistic regression was used to identify variables associated with cluster membership.
Results
Changes in body fat mass and skeletal muscle mass over the 2-year follow-up showed strong associations with cluster assignment.
Both body fat mass change and skeletal muscle mass change were closely associated with body-shape trajectories across the three clusters.
These body composition changes were identified as among the most strongly associated variables with cluster membership.
The findings highlight that changes in muscle mass, not just fat mass, are relevant to body-shape trajectory classification.
Results
Clinically meaningful worsening in sleep quality was significantly associated with membership in the Adiposity-Increasing cluster.
Worsening sleep quality was defined as an increase of ≥2.5 points in the Pittsburgh Sleep Quality Index (PSQI).
This threshold was used to define 'clinically meaningful worsening' in sleep quality.
The association was identified using multinomial logistic regression with cluster membership as the outcome.
Results
Reduced physical activity was significantly associated with the Adiposity-Increasing cluster.
Physical activity was measured using the Global Physical Activity Questionnaire (GPAQ).
A decrease in activity as measured by the GPAQ was significantly associated with the Adiposity-Increasing cluster.
Both worsening sleep quality and declining physical activity were identified as modifiable lifestyle factors linked to the Adiposity-Increasing trajectory.
Background
BMI alone was considered insufficient to characterize adiposity distribution or changes in muscle mass, motivating the use of multiple body-shape indicators.
Body-shape indicators including waist circumference, waist-to-hip ratio, and waist-to-height ratio predict metabolic and cardiovascular disease risk.
Six body-shape measures were incorporated into the clustering approach to capture a more complete picture of body-shape change.
The authors noted that few prior studies have assessed longitudinal changes in these measures together with lifestyle factors.
What This Means
This research suggests that when tracking how body shape changes over time in Korean adults, three distinct patterns emerge: people whose body shape stays roughly the same, people whose body shape reflects increasing fat accumulation, and people whose body shape reflects decreasing fat accumulation. Over a 2-year period among 1,404 participants, the biggest drivers of which group someone fell into were changes in body fat and muscle mass—not just weight or BMI alone. This finding highlights that measuring multiple aspects of body composition gives a more complete picture of how someone's body is changing.
The study also found that two modifiable lifestyle factors—getting worse sleep and becoming less physically active—were specifically linked to the group experiencing increasing adiposity (body fat accumulation). Worsening sleep was defined using a recognized clinical threshold on a standard sleep quality questionnaire, and declining physical activity was tracked with a standard activity questionnaire. These findings suggest that sleep and exercise habits may play important roles in determining whether someone's body shape shifts toward greater fat accumulation over time.
This research matters because it supports a more comprehensive way of thinking about body shape and obesity risk—one that goes beyond simply tracking weight or BMI. By identifying clusters of people with different body-shape trajectories and linking those trajectories to specific lifestyle changes, the study provides a foundation for designing more targeted lifestyle interventions. This research suggests that addressing sleep quality and physical activity, alongside monitoring body fat and muscle mass, could be important components of efforts to prevent unhealthy shifts in body composition.
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Lee J, Jeong K, Lee Y, Baek Y. (2026). Lifestyle factors and clustered patterns of body shape change in Korean adults: A longitudinal observational study.. PloS one. https://doi.org/10.1371/journal.pone.0360853