I think that right now, the most important thing since you are just getting started is to worry about your calorie level, moving a little more each day, and then trying as best you can to eat healthfully for your 1500 calories.
I wouldn't worry too much about protein, carbs, and all the macronutrients right off the bat. Baby steps.
Actually, once you get into an exercise regime-you will have MORE energy. When you are sendentary, a common side effect of that IS tiredness. When you get the oxygen and blood pumping through your body more often, you are much more energetic as a result. (That's why aerobic instructors always seem so darn perky.
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EASE into an exercise routine. Start out with some simple walking every day-even if it is only a short 10 or 15 walk per day, or one of those exercise dvds with the short sessions. Get into the habit of doing a short exercise session each day, and after it becomes a habit, then move up.
A LOT of people (especially around New Years) jump into an extreme diet plan and exercise regime, and start working out 2 hours a day...and then 3 weeks later, they quit because they burned themselves out. If you are normally sendentary, start slow to get in the habit, and then slowly advance.
The problem with worrying about protein and carbs in the beginning-is that they are not all equal. The carbs in a donut are obviously less nutritious than the carbs in oatmeal or an apple.
Instead of worrying about it right off the bat, think about nutrition instead. Does this food provide nutrients to my body? Once you get the hang of the calorie counting and start easing into exercise, then you can get more into macronutrients later.
Also, remember to be patient. The weight didn't get on your body in 3 weeks, and it's not going to go away in 3 weeks, either.