I plan to do the Oslo marathon in September. I tend to only exercise once per month, usually by running somewhere between 15 and 20 km. Yesterday I decided to cycle 50 km instead. Then today I felt that wasn’t enough so I decided to do a short 6 km run as well. But then I felt hungry as I walked out the door, so I stopped at the local shop and bought three doughnuts and two chocolate bars. After 5 km of running, my stomach was churning so much I had to stop. I suspect I need a better training regime