Just from hanging out on these boards for the last year or so I can tell you that what you are experiencing -- feeling great when starting on the new routine and then getting a massive sense of fatigue and/or hunger a few weeks later -- is really, REALLY common. Generally the people having this issue are not eating enough to sustain their level of activity; it's not just an issue of the sudden change in lifestyle. Double and triple check your ranges. A typical average height, averagely overweight woman who is not exercising is still going to need to average up to 1500 calories per day (range 1200-1550 I think). Someone who's working out moderately will need a few hundred calories more than that, perhaps 1400-1700. Someone who is exercising intensely or for long time periods, or who has an intensely physical job, might need 1600-1900; a rare few might need even higher than that.
In the long run, going too low on calories (that is, creating more than a 500-1000 calorie daily deficit) is usually detrimental. You wind up exhausted and/or starving, you're more likely to binge; you may even notice your weight loss grind to a halt as your over-stressed body starts shutting stuff down where it can to conserve energy. None of this is good for you.
So first, look at your ranges. Once that's in order, if you're still having troubles after another week or two, then consider tapering your calories down more slowly and/or decreasing your exercise for a while; many people do better that way and there's nothing wrong with it. And if it persists or any longer than that, see a doctor, because there are many reasons for fatigue that have nothing to do with how much you're eating. But most likely you just need to eat a little mroe and/or exercise a little less.
Height 5'8 1/2"
GW: Originally 150. Maintaining at about 146 since June 2013.
5K 4/21/11: 31:55
|40 Maintenance Weeks