The objective of this study was to investigate the effect of anti TNF-α therapy on nutritional status and serum leptin levels in patients with ankylosing spondylitis. This study was conducted on two groups of AS patients. First group included 48 patients receiving anti TNF-α treatment together with NSAID. Second group included 48 patients receiving only NSAID treatment. Descriptive information, food consumption and physical activity about patients collected with a survey. Anthropometric measurements were measured with body analysis scale and serum leptin was also assessed. As results, there was significant difference in daily energy consumption between both men and women with and without anti TNF-α treatment (2399 kcal and 2069 kcal p=0,036, 2102 kcal and 1659 kcal p=0,001). There was no significant difference of serum leptin levels between patients receiving anti TNF-α and only NSAID treatment (p>0,05). However, the women's leptin levels (12,4±8,2 ng/mL) were significantly higher compared to men (3,7±3,02 ng/mL). There was positive correlation of serum leptin levels, BMI and body fat mass between men and women with and without anti TNF-α treatment. The anthropometric measurements between both men and women groups were not significant (p>0,05). No statistical difference was found between the physical activity assessments of the groups (p>0,05). In conclusion, there was no significant effect of anti-TNF-α treatment in AS patients on serum leptin levels, physical activity, and anthropometric measurements. However, anti TNF-α therapy receiving patients' daily energy and nutrient consumption were higher. This study showed anti TNF-α therapy has been effective on food consumption of patients with ankylosing spondylitis.