This study aimed to compare concentrations of serum 25-hydroxy vitamin D and inflammatory markers in metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO), and to determine whether the relationship between vitamin D levels and both cardiometabolic and inflammatory markers differs between MHO and MUO.

This cross-sectional study comprised 4391 obese subjects aged>18 years. A panel of cardiometabolic and inflammatory markers, including anthropometric variables, glycaemic indices, lipid profiles, liver enzymes, homocysteine, C-reactive protein (CRP), fibrinogen and serum 25-hydroxy vitamin D levels, was investigated. All cardiometabolic and inflammatory markers in MHO and MUO as well as in vitamin D deficiency were compared.

Prevalence of MHO was 41.9% in our obese subjects using International Diabetes Federation criteria. Considering insulin resistance and inflammation, the prevalence of MHO was 38.4%. Individuals with MHO had significantly higher vitamin D concentrations compared with MUO, and this difference in vitamin D status persisted after accounting for BMI and waist circumference. Subjects with MHO had significantly better metabolic status, lower liver enzymes, lower inflammatory markers and higher serum 25-hydroxy vitamin D than those with MUO. Associations between vitamin D levels and inflammatory and cardiometabolic markers differed according to MHO/MUO status. Among MUO subjects, vitamin D deficiency was associated with higher liver marker and homocysteine levels. Serum vitamin D was negatively associated with fasting plasma glucose and HbA_1c in MHO only.

Serum 25-hydroxy vitamin D levels were lower in MUO vs MHO, and reduced vitamin D concentrations were more strongly associated with cardiometabolic and inflammatory markers in MUO than in MHO subjects. These findings suggest that a deficiency in vitamin D could be a key component of MUO.