it all depends on the severity of the fatigue and each person's constitution. good fat is good most of the time, and bad carbo is bad all the time. Good carbo is needed. Read my article " A Big Fat Lie" in my website. http://www.drlam.com
for more info. Its important for most to reduce grains, corn, and gluten to start and see.
One of the common findings is hypoglycemia in those with advance fatigue. Protein and fat therefore are better relative to carbo generally speaking as they do tend to maintain a more stable blood sugar .