Description: This book explores the close link between vitamin D deficiency and obesity, two major public health issues in Morocco and worldwide. Conducted in Kénitra, this research evaluates vitamin D status and phosphocalcium metabolism in overweight and obese people, as well as the effects of vitamin D and argan oil supplementation. The results of a one-year study involving 350 participants revealed a high prevalence of vitamin D deficiency, particularly among women. Vitamin D3 supplementation (600 IU/day) significantly improved serum 25(OH)D levels, with even greater benefits observed in combination with argan oil. These results underline the importance of vitamin D for metabolic health and suggest that local natural resources, such as argan oil, can play a valuable role in improving nutritional and public health outcomes.