If you're using Word's built-in heading styles to create your outline, this
is the reason. Headings 1-4 are formatted as "Keep with next," which means
that Word tries to keep them all together. When you insert body text, this
is the first opportunity Word has to insert a page break. If you will be
adding body text after all the heading levels, then don't worry about the
problem, which will eventually sort itself out. But if your outline is going
to be composed almost entirely of heading styles, you need to remove the
"Keep with next" property from the lower levels (say Heading 3 and Heading
4) through Format | Style | Modify: Format: Paragraph.
