Objective: To investigate the relationship between serum vitamin B12 levels and weight among the adult population in KSA.

Methods: This research will employ a cross-sectional study design to investigate the association between serum vitamin B12 concentration and obesity among adults in the Kingdom of Saudi Arabia (KSA). Cross-sectional studies are suitable for examining relationships between variables within a specific population at a single point in time. The target population for this study includes all adult residents of the KSA aged 18 years and older.

Results: The study included 869 participants. The most frequent weight among them was 51-65 kg (n= 255, 29.3%), followed by 66 -75 kg (n= 214, 24.6%). The most frequent height among study participants was 161-170 cm (n= 324, 37.3%) followed by 151-160 cm (n= 266, 30.6%). The most frequent body mass index (BMI) value among study participants was Normal 18.5-24.9 kg/m² (n= 344, 39.6%), followed by overweight 25-29.9 kg/m² (n= 281, 32.3%).  Vitamin B12 varied among study participants, with most of them having a normal range (n= 319, 36.7%) followed by a low range (n= 117, 13.5%) and the least common high range (n= 23, 2.6%). On the other hand, among 410 participants, 47.2% did not know their vitamin B12 value. Wech may indicate a lack of knowledge about the topic. Figure 4 shows the vitamin B12 levels among study participants.

Conclusion: Study results showed that most of the study participants do not know their vitamin B12 level and need to increase awareness, followed by those who have a normal vitamin B12 level. The most common BMI was the normal level. There was a relationship between vitamin B12 levels and obesity.