Word handles pictures differently when they are cut and pasted than when they are inserted. When you cut and paste an image into your Word document, Word treats it as TIFF file, which is much larger typically than JPG files, even if the image you started with was a JPG!
When you insert images into your document correctly, using the Picture tool, you can save tons of disc space and communication bandwidth if you have to e-mail your document. An added bonus is that your file will now load faster and you can more quickly make edits!
You learn something new every day. Thanks!