Hi Sistaworkin,
If you have cut back on your caffeine, sugar, or iron you could be low in energy from that. If you have any history of iron deficiency get your level checked to see if you need to take a supplement. Iron can be toxic in high levels so it's not a good idea to take it if you don't need to.
Caffeine can give a boost of energy. I do not recommend the energy drinks as your source of caffeine. It would be best to get it from coffee or green tea. You will also want to drink enough water in your day so include it along with the caffeinated beverages. If your going long periods without eating try having a piece of fruit in between. Be sure to choose fruit with the skin on it for the fiber and count the calories in with your plan.
The other option is to increase your activity. It may be the last thing that you feel like doing when you are low in energy but even a short walk will have an impact.
Good luck,
Betty Kovacs, MS, RD