# Correlation between serum trimethylamine-N-oxide and body fat distribution in middle-aged and older adults: a prospective cohort study

## TL;DR

This study found that higher levels of TMAO in the blood are linked to increased fat accumulation in the trunk area of middle-aged and older women over time.

## Contribution

The study reveals a novel gender-specific association between serum TMAO and longitudinal changes in body fat distribution in women.

## Key findings

- Women with higher TMAO levels showed greater increases in trunk fat-to-lean mass ratio and trunk-to-leg fat ratio over six years.
- Linear mixed-effects models confirmed significant annual increases in trunk fat distribution for women in the highest TMAO tertile.
- No significant associations were observed in men, highlighting gender differences in TMAO's impact on fat distribution.

## Abstract

Trimethylamine-N-oxide (TMAO) is linked with obesity, while limited evidence on its relationship with body fat distribution. Herein, we investigated the associations between serum TMAO and longitudinal change of fat distribution in this prospective cohort study.

Data of 1964 participants (40–75y old) from Guangzhou Nutrition and Health Study (GNHS) during 2008–2014 was analyzed. Serum TMAO concentration was quantified by HPLC–MS/MS at baseline. The body composition was assessed by dual-energy X-ray absorptiometry at each 3-y follow-up. Fat distribution parameters were fat-to-lean mass ratio (FLR) and trunk-to-leg fat ratio (TLR). Fat distribution changes were derived from the coefficient of linear regression between their parameters and follow-up duration.

After an average of 6.2-y follow-up, analysis of covariance (ANCOVA) and linear regression displayed women with higher serum TMAO level had greater increments in trunk FLR (mean ± SD: 1.47 ± 4.39, P-trend = 0.006) and TLR (mean ± SD: 0.06 ± 0.24, P-trend = 0.011). Meanwhile, for women in the highest TMAO tertile, linear mixed-effects model (LMEM) analysis demonstrated the annual estimated increments (95% CI) were 0.03 (95% CI: 0.003 – 0.06, P = 0.032) in trunk FLR and 1.28 (95% CI: -0.17 – 2.73, P = 0.083) in TLR, respectively. In men, there were no similar significant observations. Sensitivity analysis yielded consistent results.

Serum TMAO displayed a more profound correlation with increment of FLR and TLR in middle-aged and older community-dwelling women in current study. More and further studies are still warranted in the future.

NCT 03179657.

The online version contains supplementary material available at 10.1186/s12937-024-00974-w.