Originally Posted by Tundra_Man

I've been doing the 5:2 plan for the last nine months. Five days of eating normally (normally = sensibly, not stuffing yourself silly) and two days of "fasting" (< 500-600 calories.)

The "plan" says you can split up the calories on fast days in whatever way works for you. For me, I usually save most of my calories for the evening meal. Sometimes I'll have a big plate of lettuce or raw veggies at lunch. Supper is a small portion of whatever the rest of the family is having. The first couple of weeks were pretty rough while getting used to not eating anything all day, but it got easier and easier as time went on. Now that my body has adjusted, I'm hungry on fast days but it's no worse than I am on a non-fast day when mealtime is approaching. My mantra when I was feeling the intense hunger pains was, "You're not going to die by skipping a meal. You're not going to die by skipping a meal. You're not going to die..."

I still ride my bike to work and home every day, and often tack on extra miles just for fun/exercise. I haven't noticed any loss of energy one.