The 55th Scientific Meeting of the Nutrition Society, held in Birmingham on 15 October 1949, focused on triglyceride fats in human nutrition. T. P. Hilditch discussed the chemical composition of natural fats, emphasizing that they are complex mixtures of mixed glycerides, with each triglyceride following a general rule of even distribution of fatty acids. This rule holds true for most natural fats, except for certain animal depot fats and milk fats, where specific glyceride types result from biochemical modifications. The composition of natural fats is largely determined by the proportions of fatty acids present, with palmitic acid being a common component in animal fats. In depot fats, palmitic acid typically constitutes 25-30%, while oleic acid is the main unsaturated acid. In liver fats, the composition includes phosphatides and glycerides, with a higher proportion of unsaturated acids. Milk fats vary in composition, with some containing significant amounts of saturated acids like butyric and lauric. The synthesis of storage fat by animals involves converting carbohydrates into fat, with palmitic, stearic, palmitoleic, and oleic acids being synthesized. Assimilated dietary fats are influenced by their molecular size and the animal's ability to utilize fatty acids. Vegetable fats are generally more unsaturated than animal fats, with a wide range of fatty acids. Marine animal fats have a distinct composition, with a higher proportion of unsaturated acids. Hydrogenated fats, produced by partially hydrogenating oils, have a different composition from the original oils. The study highlights the importance of analyzing fatty acid proportions in fat metabolism and the limitations of using iodine values and molecular weights for this purpose. The composition of fats is crucial for understanding their role in human nutrition and metabolism.The 55th Scientific Meeting of the Nutrition Society, held in Birmingham on 15 October 1949, focused on triglyceride fats in human nutrition. T. P. Hilditch discussed the chemical composition of natural fats, emphasizing that they are complex mixtures of mixed glycerides, with each triglyceride following a general rule of even distribution of fatty acids. This rule holds true for most natural fats, except for certain animal depot fats and milk fats, where specific glyceride types result from biochemical modifications. The composition of natural fats is largely determined by the proportions of fatty acids present, with palmitic acid being a common component in animal fats. In depot fats, palmitic acid typically constitutes 25-30%, while oleic acid is the main unsaturated acid. In liver fats, the composition includes phosphatides and glycerides, with a higher proportion of unsaturated acids. Milk fats vary in composition, with some containing significant amounts of saturated acids like butyric and lauric. The synthesis of storage fat by animals involves converting carbohydrates into fat, with palmitic, stearic, palmitoleic, and oleic acids being synthesized. Assimilated dietary fats are influenced by their molecular size and the animal's ability to utilize fatty acids. Vegetable fats are generally more unsaturated than animal fats, with a wide range of fatty acids. Marine animal fats have a distinct composition, with a higher proportion of unsaturated acids. Hydrogenated fats, produced by partially hydrogenating oils, have a different composition from the original oils. The study highlights the importance of analyzing fatty acid proportions in fat metabolism and the limitations of using iodine values and molecular weights for this purpose. The composition of fats is crucial for understanding their role in human nutrition and metabolism.