Assalam o alaikum
Fasting has two fold opposite effects on sexual life. First it reduces the urge for sex and second it strengthens the capability for sex. Here is why;
First of all let's understand the act of eating. We eat so some parts of food go to our body through digestion and do couple of important things for our living including energy creation and minerals creation that help our body in functioning. There are 2 centers in our body that send demand signals to brain; first is our stomach when it gets empty and second is any part of our body which feels requirement for minerals and/or energy. Whenever the digested food is more than our requirements, that food is stored. Although our body uses energy to regulate the stored food and remove any spoiled food particles but it becomes very difficult with increase in stored food.
Now let's understand the act of sex. Well no much explanation, everybody knows, just need to understand that sperms need heavy bodyguard force when they release from our body and that bodyguard force is few very important minerals that our body got from the food. 2 centers send message to brain for sex desire; first is sperms production center and the other is entire body which feels heavy in minerals required to travel with sperms. These minerals always keep travelling from whole body to sperms point and most quickly after sex.
Now let's understand the act of fasting. During fasting our main objective is to stop supply of food to our body where there is already much food stored. Our body has to use that stored food for its needs and as a result a cleaning process takes place when we fast again and again. During fasting practice our body keeps very low quantity of minerals that need to travel with sperms so our sex urge is substantially lowered. After fasting practice, our body gets fresh and our body parts start working with more accuracy. That also affects the sperms production and working of entire sex system. Sex organs get healthier and due to lack of allied minerals sperms make delay in releasing so sex timing increases and given a healthier experience, although at start the urge was very low which is the point here.
Now last thing for those who are wondering; we eat so much before and after fasting that our body never has to use stored food, it never cleans body parts. Our stomach remains full during most of the fasting time and as a result our body gets all minerals and energy and never feels a decrease in sex urge.