Cole is suffering from Focal segmental glomerulosclerosis (FSGS) and the 44-year-old was diagnosed with the illness last summer.
Speaking in a candid interview on the BBC's Football Focus programme Cole said: "That's been the toughest part for me, putting on all the weight.
"So seeing the change in your body that's been really tough. The weight you've put on through water retention wreaks havoc with your head because you're saying to yourself 'I don't want to look in the mirror anymore because you're not the same.
"You don't feel the same, you don't feel as confident about yourself as you used to, but then it's out of your hands.
‘’I kept out of the public domain for a hell of a long time, about six months or so. I wouldn't tell a soul.
"You're getting all these comments 'Andy Cole, he's put on all this weight', 'who ate all the pies?' and all that kind of stuff."
Cole felt ill when he returned from a trip with Manchester United to watch players in Vietnam and originally put off going to see doctors for a diagnosis.
He then had to spend a month in a Manchester hospital after being told the disease had reduced the function of one of his kidneys to less than 20 per cent.
Inadvertently, an invite by former Old Trafford team-mate David Beckham to play in a charity game prompted Cole to go public about his condition.
"Becks asked me to play in his match the charity game for Unicef and I was desperate to play in that," he said.
"Sir Alex Ferguson let the organisers know that 'Coley's got no chance of playing because he's been ill'.
"So that's when I said 'look, I'm going to have to come out and put a statement out regarding my illness.
"People were questioning my weight and my appearance and things like that. Now I've actually come out with it everyone was saying 'Oh, wow, we didn't know.