The simple answer is yes. A lamb is up to one year of age, and the meat has little fat. Spring lamb is less than three months of age, and this meat is extremely tender but has a milder flavor than regular lamb. Mutton is meat from a sheep that's older than one year and typically closer to three years of age. It has more fat and a stronger flavor compared to lamb. Lamb is more popular in the United States, while mutton is more common in the Middle East and Europe.