Interesting Book

I recently borrowed this book from the public library.

The title intrigued me...

I'm not sure that I completely understand the answer to the riddle posed by the book's title. (I did skip pages here and there!) 

I THINK the answer is that some macroingredients in food, like fiber, (and hence their calories) pass through the body undigested without "adding" calories.

But I did find the book "life changing" in a way because it brought home the importance of eating fruits and vegetables in their natural state, (i.e, without added sugar) because they provide the body with lots of fiber. I used to think of fiber mostly in terms of "bran" - but I no longer do. Fruits and veggies have fiber too.

I have started to add a greater variety of fruits and vegetables - hence "fiber" - to my diet.

I've also decided to try to avoid "ultra-processed" food, though it can be so convenient - partly because it's pre-packaged, too.

My new "test" for untra-processed food: Do I have the last 3-5 ingredients listed on the package in my kitchen cupboards?