He said he had tried to stay fit during his 12 years in Parliament but never to this level.
Meanwhile, Rotorua Marathon race director Murray Fleming said entries were tracking "really well".
"There are so many events now, most entry numbers are dropping because the market is so saturated but we are on track for 3500 runners across all of Saturday's events, up from 2800 last year."
Today 2500 primary school students will complete the final 2.1km of their "Mini Marathon" outside the Energy Events Centre
When the runners from all over the Rotorua District and Tauranga race, it will be the last of 40km of running (or walking) in their training diary in the build-up to the official marathon event.
Rotorua Marathon Road Closures, Saturday May 5:
Queens Drive from 6am to 6pm, Hinemare St southbound, from Arawa St to Amohau St (7.45am to 6pm), one half of parts of Arawa St, Ranolf St and Lake Rd (7.45am to 10.30am), Fenton St from Arawa St to Whakaue St, both sides (7.45am to 10.30am), Hamurana Rd from Unsworth Rd to SH33 at Mourea (9am to 1.30pm)