Hi Singer!

Yes, it's perfectly normal to feel cruddy for the first week or so. It's a big adjustment for your body to go from using sugar for energy to using fat and it's letting you know that it's not happy about it (at least not right now). On the other hand, here are a couple of other things to check as well: first, are you drinking enough water? Dehydration can make you feel tired and lethargic. You should be drinking at least eight 8 oz. glasses of water a day (tea, coffee and diet pop do not count). Second, are you taking any supplements? Low potassium can also make you feel tired and achy and supplementing with one or two 99 mg. tablets daily can help, but check with your doctor or pharmacist first if you are taking any medications for blood pressure or diuretics; some can make you retain potassium so taking more could be dangerous.