I know this question is quite old but I had the energy problem too when I first tried fasting. I felt hyper but couldn't actually harness the energy, so I did some research and found the following

Paleo for Women | Shattering the Myth of Fasting for Women: A Review of Female-Specific Responses to Fasting in the Literature

Should Women Fast? | Mark's Daily Apple

I cut back trying to fast for more than 12 - 14 hours at a time, fasting from dinner one night to 10 - 11am the next day, which I found very easy. As time went on I would forget to eat until later & later the next day, with no ill effects, until I was doing 18 - 24hr fasts easily. This took about 6 weeks. I now do a weekly 42 hr fast from dinner one night, to late afternoon two days later and find I have my best night sleep the second night.
I'm menopausal though, not very active (I walk the dog for 30 mins once or twice a day, & try and cycle 2 miles, every couple of days), and very overweight, so I'm not sure if these points a relevant to you, but fasting is different for women from men.