Obesity is a major global health concern, and while BMI is a common assessment tool, it doesn't fully capture the heterogeneity of obesity and its associated health risks. Visceral fat accumulation, measured via methods like CT or MRI, is strongly linked to cardiovascular and metabolic diseases, but these techniques are costly and time-consuming. Neck circumference (NC), a simple anthropometric measure, has shown promise as a quick and convenient alternative. Previous cross-sectional studies have demonstrated a positive association between NC and visceral fat area (VFA), but longitudinal data is lacking. This study aimed to determine if changes in NC over time are associated with changes in VFA and the development of abdominal obesity in a Chinese community-based cohort.

Existing literature highlights the limitations of BMI in assessing obesity's diverse health implications. Studies emphasize the crucial role of visceral fat distribution in cardiovascular and metabolic diseases. While CT and MRI are gold standards for VFA assessment, their impracticality for widespread clinical use necessitates simpler, readily available alternatives. NC, due to its ease of measurement and high repeatability, is gaining attention as a potential surrogate marker. Prior cross-sectional studies in Chinese populations have established optimal NC cutoff points for estimating abdominal obesity. A Japanese study showed a positive correlation between NC changes and changes in waist circumference and body fat in postmenopausal women. However, longitudinal studies specifically examining the relationship between NC changes and VFA remain scarce, prompting this research.

This longitudinal cohort study recruited participants from Shanghai communities between 2013 and 2014, with a follow-up period from 2015 to 2016 (1.1–2.9 years, average 2.1 years). A total of 1421 participants (578 men, 843 women) aged 24–80 (mean 57.8 ± 7.1 years) were included after excluding those with certain conditions. At baseline and follow-up, anthropometric measurements (including NC, weight, height, waist circumference (WC), and blood pressure) and biochemical measurements (fasting blood glucose, fasting insulin, lipid profile, glycated hemoglobin (HbA1c), and C-reactive protein) were collected. VFA and subcutaneous fat area (SFA) were assessed using 3.0T MRI. Abdominal obesity was defined as VFA ≥ 80 cm². Statistical analyses included matched samples t-tests, Wilcoxon rank-sum tests, linear regression (to assess the relationship between NC changes and VFA/SFA), and logistic regression (to analyze the relationship between NC changes and abdominal obesity). NC change was categorized as <-2.5%, -2.5% to <2.5%, ≥2.5% to <5%, and ≥5%.

The study found that after adjusting for age, sex, BMI, smoking, drinking history, HbA1c, blood pressure, and blood lipids, individuals with a NC increase of ≥5% had 1.26 times more visceral adipose tissue at follow-up compared to those with stable NC (-2.5% to 2.5%). In the group without abdominal obesity at baseline (n=683), after adjusting for confounding factors, NC changes were significantly associated with subsequent abdominal obesity (odds ratio 1.23, 95% CI: 1.09–1.39). A 5% increase in NC was associated with a 36% increased risk of abdominal obesity. There was no significant association between NC changes and subcutaneous fat area.

This study provides strong evidence for the association between changes in NC and VFA, supporting the use of NC as a practical screening tool for abdominal obesity. The consistent positive association between NC change and VFA, even after adjusting for several confounding factors, highlights the independent contribution of NC changes to visceral fat accumulation. The findings align with previous research suggesting that NC reflects upper body fat accumulation, which is strongly linked to metabolic abnormalities. The study's strength lies in its longitudinal design, which better captures the dynamic relationship between NC and VFA compared to cross-sectional studies. The use of MRI for VFA assessment provides a robust gold standard measure.

This Chinese community-based longitudinal cohort study demonstrates a significant positive correlation between changes in neck circumference and increases in visceral fat area, suggesting that neck circumference can serve as a supplementary index for evaluating abdominal obesity in clinical practice. Future research could explore the generalizability of these findings across diverse populations and investigate whether interventions targeting NC changes could effectively reduce visceral fat accumulation.

The study's limitations include potential selection bias inherent in epidemiological studies, its single-center design limiting generalizability beyond the Shanghai community, and the possibility that aging or other diseases might influence NC measurement. Further research in diverse populations and the incorporation of imaging to control for factors affecting NC measurement would strengthen the findings.