In terms of acquiring this knowledge, there is good news and bad news. The bad news is that the actual truth of this information can be a little hard to find. There are countless sources of misinformation and agenda based pseudo science to push certain viewpoints and products. At best even when you find solid information, there are some conflicting arguments that are equally valid, where only trial and error can determine the best approach. The good news is that once you find a good source of information - the truth about what the people who live with the lean muscular bodies that they desire really do it is actually reasonably easy to understand and achieve an excellent working understanding of it all. With someone who really knows what they are doing and sources of honest truth in your corner, it is no exaggeration to say that your comprehension of nutrition and training will outstrip many people in the fitness industry in about a month or even less.