Reddit reviews Exercise Metabolism - 2nd Edition (Hardcover Book)

If you really want to understand nutrition, and not just listen to what (mostly unqualified) people tell you what they think nutrition is, read a physiology text book.

You can buy old textbooks pretty cheap of ebay. These are texts designed for undergraduates with limited knowledge of biology (usually just bio 101). Even if you haven't had a bio101 type class, if you read the first two chapters it should tell you everything you need to know to understand the rest of the book.

If you understand the physiology, then you can easily deduce proper nutrition without having to listen to someone else.

Human Physiology

Exercise Metabolism