The science of Pure Food has been discussed in many books of Ihsan. I thought I might give a short and basic introduction. Perhaps someone will benefit from this information more than I did.
The food you eat will be used for acts of worship so make sure it is halal! We hear many stories of heads of companies unapologetically insulting things that are sacred to Muslims. We should leave them. If you are visiting someone whose income is derived from impermissible transactions, do not eat their food. As for meat, there is a difference of opinion in regards to super-market meat. And remember, everything is assumed to be halal unless a source of Islamic Law ( , hadith, scholarly consensus, and analogy) make it haram. However, avoiding the doubtful is the higher road.
Preserve the heart also from haram. Guard the sight and hearing for they are both pathways to the heart. In addition to avoiding seeing and listening that which is haram, one should avoid things that other people have. For example, if someone sees a nice car they do not have, they might desire it. This desire itself is blameworthy to a certain extent (I won’t say halal or haram because I am not a mufti). This desire could even turn into envy, may Allah save us from such diseases of the heart. This is one of many examples. Cancel out the bad and bring in the good by making thikr and reading Quran often.
Another aspect of this is ta’thim (I guess a good translation might be “reverence”) of the food. Do not be heedless of the fact that each cup water and each bowl of food is a huge gift from Allah. An ascetic went to Imam Harun Rashid and asked him “if you were dying of thirst, would you give half of your kingdom for a cup of water?” The Imam answered “Yes.” Then the ascetic asked “Then how much is your kingdom really worth?” Remember that as you eat. And always eat intending to use the caloric intake for halal. The higher level of this is to intend to worship with the food.
Eat healthy. Our bodies are gifts from Allah so preserve them. If your friend gave you a gift, would you be careless of it while he was watching? Avoid fatty and The Prophetic Medicine.and exercise. I also suggest buying a copy of
Finally, there is the topic on smoking and hookah pipes. Both of these are haram because there is great harm in them. Here is a good khutba about smoking and its ruling. http://naseemalsham.com/stream.php?ID=289
And Allah knows best.