Bill felt changes almost immediately after Dave set down the pen.
"What did you write?" Bill asked in his very deep, baritone voice.
Rather than respond Dave simply threw the piece of paper into the bin by the desk and gave him a 'wait and see' smirk.
Bill looked at his uniform, and saw it was growing larger. In fact, it wasn't just his uniform, it was him! Bill's newly found muscles faded away, and were replaced with jiggly fat.
He watched in shock as his belly ballooned outwards, stretching his uniform to the limits, with his gut and serious man-tits showing through the shirt. He felt his utility belt move several notches up to compensate for his expanding waistline, and saw his arms and fingers grow thicker to match.
Bill was discovering that not only did he not miss his muscled physique, but that he really liked this feeling of being 'large and in charge' (Dave has increased his height to 6"2 from his usual 5"11), his round gut and deep voice creating a very intimidating impression.
His legs widened, but his Security Guard trousers prevented them from growing obscenely big, rather becoming thick trunks to support his growing bulk.
The last thing to change was his face, which grew rounder, bulges of fat building up at the back of his neck where his collar fit under his large double chin.
The change ceased, and Dave smiled at William, the companies widest and only 'non-American' member of the Security Staff. He had also changed Bill's memories to make him think he had always been an obese Security Guard, and had given him a slightly lower IQ to match the stereotype.
Bill looked at his (new) body, enjoying the experiences that came from living on the larger side of life. He placed his thick thumb between his trousers and his boxers, which felt natural to him. He smiled at Dave, one of the companies friendlier workers, whom 'William' knew relatively well.
"Well, I'd best get back to work." William said cheerfully, making a mock salute at Dave as he turned his large figure (careful not to let his protruding belly knock any papers of the rows of desks that had always been too narrow for him) and waddled away, smiling at people as he walked past, unsurprised how they simply ignored some one as insignificant as 'the fat token security guard'.