Why some aminoacids are both glucogenic and ketogenic?

Some amino acids are classified as both glucogenic and ketogenic because they can be converted into both glucose and ketone bodies, depending on the metabolic needs of the body. For instance, during periods of fasting or low carbohydrate intake, these amino acids can be broken down to produce acetyl-CoA, which can be used for ketogenesis. Simultaneously, they can also enter gluconeogenesis pathways to generate glucose when energy levels are low. Examples of such amino acids include isoleucine, phenylalanine, tyrosine, and tryptophan.