The 52-year-old revealed he would go days without eating, relying on coffee to boost his energy levels and making himself ill if he had a meal.
And he reckons he could have done even better than his Olympic silver medal and two World Championship victories if he had not suffered from the eating disorders.
BBC pundit Jackson said: “I felt like I was overweight and eating too much. I had a job to do and it was to run as fast as I could, and I convinced myself that I had to be lighter to do it.
“I wanted to weigh less, so I’d be sick or eat a lot less than what’s required to sustain a normal healthy body.
“On reflection, I would have been an overall better athlete and a lot happier with myself if I hadn’t suffered with bulimia and anorexia.”
The Welshman, who still holds the world record for the 60m hurdles, eventually beat his disorder when he retired from the sport.
He has urged fellow eating disorder sufferers to ask for help.
Jackson explained: “As soon as I retired, there wasn’t the burning necessity to change to compete. It’s a hard thing to look in on when you’re in that situation yourself.
“My advice would be to stop and ask yourself: ‘Is this good for me, am I healthy?’
“It’s easy to say this now I’m out the other end, but I do encourage people who suffer with an eating disorder to stop, don’t do it, don’t criticise your appearance, love yourself, be confident and believe in your abilities.
“Ask for help, don’t feel alone, reach out to people close to you.”
● If you are worried you may have an eating disorder, email Beat at firstname.lastname@example.org, or call 0845 634 1414.