Great changes. He would literally be a walking zombie on some days, when he had his tests done they were telling him his oxygen level was dropping so low at night that he would probably die within a few years if he either didn't lose weight or use a CPAP machine.
He came in and told us that the first night he put the mask on he slept for 17 hours strait without even rolling over or moving once. His wife was scared because she thought he was in a coma, but after a couple of days of actually sleeping normally he was alert for the first time in years.
He would snore, then get really quiet for a while, then gasp really loud, take a breath, then fall back asleep. He was waking up three to four times a minute all night long to make himself breath, his throat was closing down because of his weight and he literally choked all night long.
It is quite common for heavy set people to have this problem, the machine pumps air into your nose and pressurizes the air passage, blowing your throat open like a balloon, letting you sleep and breath at the same time. His wife also slept better because he wasn't snoring and waking her up all night long too.