Stephen Morrison, who lost more than 10 stones after first getting involved in a step challenge with colleagues at work and is backing Active 2014, will be attending the meeting in Edinburgh today.
An adviser on obesity issues, he said: "The premise is that more physical activity will help reduce the impact of non-communicable diseases, such as diabetes, heart disease and strokes. How can we get more people to be active, but make sure people also know the impact of exercise?
"I have experience of this personally, when I was obese I suffered from diabetes, sleep apnea, muscle pain, back pain, I had problems breathing - all these things were reduced by being more active."
Doctors gathering at the conference on sports and exercise medicine will be warned by a leading international expert that too many Scots are "sleepwalking into obesity" and that Scottish obesity rates could reach that of the US if we do not change our approach to health and consider creative solutions such as prescribing exercise to increase physical activity.
The event has been organised by the Royal College of Physicians of Edinburgh (in collaboration with the Royal College of Surgeons of Edinburgh), as Scotland prepares to host the Commonwealth Games in July.
During his keynote presentation a leading international expert on obesity, Professor Steven Blair, Arnold School of Public Health, University of South Carolina, US, will challenge scientific and medical understanding about the causes of obesity.
He will highlight that much of our understanding about obesity is flawed as the majority of the published international evidence in relation to the causes of obesity focuses primarily on increased dietary intake and consistently ignores the positive effect of total energy expenditure.
Prof Blair said: "Regrettably, much of the international published scientific literature on the causes of obesity is flawed as it places an over-emphasis on dietary intake, at the expense of measuring the positive effect of physical activity.
"Obesity rates continue to rise and in international obesity terms, Scotland is not far behind the US. If we wish to prevent levels in Scotland reaching that of the US, greater emphasis has to be placed on exercise.
"This could involve creative solutions such as considering the provision of exercise advice, or indeed the prescribing of exercise, to patients by doctors and other health professionals. An entire industry has built up around diet, but reducing our dietary intake alone will not solve our problems with obesity.
"Physical inactivity has become the biggest public health challenge of the 21st century and we have to become more active if we are to stop collectively sleepwalking into obesity. In simple terms, we are talking about changing the mind set from thinking "I must go on a diet" to "I must become more active"".