After nearly a year of commuting by bicycle to and from work 2-3 days per week, I have recently started cycling to work every day, 5 days a week, rain or shine. My commute is about 11-15 miles each way (depending which route I take), including some steep hills (followed by stop signs, so I don't even get the benefit of coasting down-hill). I obtained a new road bike of decent quality along with reasonable quality clipless shoes, gloves, shorts, a jersey, and a heart rate monitor. I am not very physically fit (5'9" 200 lbs), but improving. Now 2 weeks into daily commuting plus occasional weekend riding, I am feeling very sore and fatigued and can barely sustain 80% of the effort I was achieving at the start.
What should I eat (and when should I eat it) to help me sustain this effort, yet also help me lose weight and improve my physical fitness? Is it important to ride at a relatively low effort level, keeping my heart rate in the base zone, or should I occasionally push it into aerobic endurance or even anaerobic zones? What heart rate(s) should I aim for? What cadence should I try to maintain?
Any advice from experienced commuters in a similar position would be greatly appreciated.