What is the correct intention for any worldly deed, such as marriage or weight loss, so that it is purely for Allah alone, and is the intention of improving one's appearance for weight loss considered wrong?

A Muslim is one who submits to God and is obedient to His law. He worships God because He is his Lord and Creator, and thus he maintains the intention of drawing closer to God in all aspects of his life. He seeks reward for his sleep, eating, drinking, marriage, and his desire for righteous offspring, all for the sake of God. He strives for his speech to be good and his silence to be a restraint from evil, and he hopes for reward in his spending on himself and his family. His intention in all his actions is for the sake of God. It is incumbent upon a Muslim not to engage in permissible acts إلا that which helps him in obedience, and he intends by them to seek assistance in obedience. This can be summarized in two points: adhering to the Sharia and avoiding forbidden things, and observing how an action can lead him to reward and closeness to God. For example, losing weight with the intention of maintaining health to perform duties, or adorning oneself for one's wife, or for good communication with people, are good intentions for which one is rewarded. However, if the intention behind permissible acts is to imitate disbelievers or to cause temptation, then this deserves sin. Permissible acts do not bring reward unless one intends them for the realization of a good purpose, for a permissible act transforms into a recommended one through intention. It has been authentically narrated from the Prophet, peace and blessings be upon him: "You will not spend any expenditure seeking thereby the Face of Allah except that you will be rewarded for it, even that which you put in the mouth of your wife." This indicates that if a permissible act is intended for the sake of God, it becomes an act of obedience and is rewarded. This is not obligatory or binding. So, whoever only intends to fulfill his psychological desire or satisfy his lust, there is no sin upon him, but he does not receive a reward merely for that action, just as there is no sin upon him.