Is it permissible to supplicate for changing the appearance of a thin body to that of youth, or is this considered a dissatisfaction with Allah's decree and destiny?

The most effective remedy for someone afflicted by worry or sorrow is to turn to Allah with sincerity and supplicate to Him, as mentioned in the Holy Qur’an regarding the supplication of the distressed, and in the noble Prophetic Sunnah with the saying: "O Allah, I am Your servant, the son of Your servant..." and other supplications that relieve worries and dispel sorrows. There is no religious impediment for a servant to supplicate for whatever good they desire in this world and the Hereafter. The servant’s supplication for well-being does not contradict contentment with divine decree; rather, it combines patience with supplication. The servant must also take the means of healing and consult a specialized doctor.