Does Islamic law place a restriction on a Muslim's weight gain, based on the fact that the Prophet, peace and blessings be upon him, was not obese?

Obesity is condemned in Islamic law if it results from excessive eating and laziness, not from old age or genetics. It is mentioned in the noble Hadith that among the signs of the End of Time is the appearance of corpulence in people "who bear witness but are not asked to bear witness, who betray and are not trusted, and who make vows but do not fulfill them." Scholars have interpreted this to mean those who intentionally become corpulent through excessive eating, drinking, and luxury, not natural corpulence or that resulting from old age. Indeed, the Prophet Muhammad, peace and blessings be upon him, himself became slightly corpulent in his later life due to old age, but it was a moderate, not excessive, corpulence.