Good for you writing your first book. I think it is wonderful! Everyone has given you positive feedback on this. It's great to get positive feedback. If no one attempts to critique it you won't know where and why to take a second look. It would be good if you could get a couple more sets of eyes on this book to help you edit it. It needs editing.

I did not read the first chapter in depth but I would like to offer suggestions for you to consider. I hope you find them helpful.

Some things to take a second look at, tense agreement, subject and verb agreement, weasel words, contractions, and punctuation. If you can't quote off the top your head the rule dictating the use of dashes, it is best to stay away from them. Quick example of s & v agreement: (What you need is the pieces of information necessary for a sustainable change – and...) "need ARE the pieces" or if you prefer "need is the INFORMATION"

I don't know how many pages your book is going to be but if you are self publishing it perhaps think of marketing as a "guide". People tend to be more forgiving of "guides" than books. Perhaps this is going to a publisher and I missed it. If that is the case I am sure that they will address the grammar and length issues.

I have no doubt if I sat down and talked to you I would learn a few things about fitness. I think you have something to offer. However, in the first chapter you keep interrupting yourself. In one statement you tell me that I can learn a great deal from you, then in the next statement you tell me your no expert. Pick a side. I understand you don't have a Professional Trainer background. About the time I get into reading and hearing your message, you interrupt the flow with "I don't know what I am talking about. Don't listen to me." statements. I understand what you are trying to accomplish with your disclaimer, and it is good to do this. What you need to do is gather them all up, put them in one place, edit it down for length, and then be done with it. Otherwise you're undermining your authority. Example (Don’t think of this book as a perfect guide. There’s mountains of knowledge out there – search for it, find it and apply it, and use your common sense. Knowledge is worth nothing if not applied.) Don't tell me to search for it, that is why I am reading your book.You are trying to establish yourself as an authority. So stop teetering, step up, and teach your reader. That is why we are here. We all know that there is a vast amount of knowledge "out there". In writing your book you are inviting the reader into your universe. Quit abandoning them and kicking them out.

The last thing; and especially if this is going to be readable online, if you don't have it, don't call attention to it. Example(I’m taking the scientific knowledge and breaking it down to digestible information to tell the story of how I found a balance...) Perhaps you have all sorts of links and citations in your subsequent chapters but if you don't have that information handy for your reader to reference then don't present it as such. If I walked up to you and said, "I just had the best protein bar!!!" You might say, "Great, what is it?" You would walk away saying, "What's the point?", if I followed up that statement with, "I don't know. I just wanted to bring it up." You are implying this when you bring up scientific and then there is no follow up.

Your reader isn't necessarily looking for you to be an expert. They are looking for knowledge. Stand up there tell us what you know, stop apologizing for what you don't know. Nobody is expecting you to be "everything". Tell me what you do REALLY GREAT, keep your book limited to that scope and we'll all have a fantastic time.

I think I understand the style you are going for. You might want to check out
The EveryGirl's Guide to Diet and Fitness: How I Lost 40 lbs and Kept It Off-And How You Can Too! By Maria Menouno and The Badass Body Diet: The Breakthrough Diet and Workout for a Tight Booty, Sexy Abs, and Lean Legs by Christmas Abbott

Both books are written in the style that you are attempting to script your book in. Maria's is more polished than Christmas's but I think it would be beneficial to look at both. You may be able to see a progression from your style, to Christmas's style, and to Maria's style.

I hoped I helped you some and gave you some of what you are looking for, because I find it interesting. I want to know what worked for you.