Dasselaar (39) completed his first marathon in Dunedin on Sunday in 3hr 51min 55sec.
A Dutch national and journalist by profession, he has been mainly self-employed since 2002, completing freelance projects and lecturing at various universities and polytechnics in the Netherlands, Canada and New Zealand.
It was when he saw himself addressing a workshop on research for Dutch broadcasters that he was shocked into changing his lifestyle and getting his weight under control.
He had become reclusive and, because he found himself always working, turned to food for company.
''Once I started reprioritising stuff, it turned out I had all the friends I could ever wish for,'' he said.
''I just ate a hell of a lot more than you could possibly hope to burn off,'' he said.
He began what he termed ''Operation Walrus'' in January 2013, involving a self-imposed weight-loss programme and lifestyle changes.
By year's end, he was a shadow of his former self, having shed a whopping 70kg in 11 months.
Dasselaar was encouraged by the support he received from friends.
This encouraged goal-setting and transition to new pursuits, such as snowboarding.
He is now based in Christchurch and enrolled at the Christchurch Polytechnic Institute of Technology for a Certificate in English Language Teaching to Adults.
His yet-to-be-released book shares his journey from 154kg to 83kg, but he is coy as to the secret of his weight-loss success.
''Like Schrodinger's cat, some things have a tendency of dying prematurely should too many eyes gaze upon them,'' he said.
