Fast while in a state of janaba if you don't perform wudu'. Eat moderately.

This hadith is about the Prophet Muhammad's practice of fasting even when he was in a state of janabah, which is when one has sexual intercourse or experiences an ejaculation due to any other reason. Umm Salamah narrated that she brought the Prophet some grilled ribs and he ate from that, then got up and prayed without performing wudu'. This shows us that it is permissible to fast while in a state of janabah, as long as one does not perform wudu' before praying. It also teaches us the importance of moderation in our diet; even though it was permissible for him to eat grilled ribs, he did not overindulge but instead kept his meal moderate.