I started the C25K a week before my 50th birthday, I have a pretty sedentary job and I had some recent weight gain due to some medication I am taking, so I decided to give C25K a go to both shift some weight and improve my fitness.

I am doing really well, better than I expected given my age an level of fitness before I started this, I am completing the runs just fine so far and feel great on the days that I run (I tend to get up early do my run at the start of the day).

It's the down days that are the problem, I am totally lacking energy and pretty much falling asleep standing up by the end of the day. Last night I slept for a solid seven hours and I am sitting typing this before I leave for work and I could in all honesty crawl right back into bed now.

I am eating well, my calorie intake is between 1500 to 2000 per day. I am drinking plenty of water.

Has anyone else experienced this and what changes did you make to improve things?