There are substantial typos in the original post, enough to cause confusion. Here is the original question again, cleaner.
When deprived of carbohydrates, its preferred fuel, the body is forced to burn fats and protein for energy, thus causing the formation of fatigue inducing toxins.
(A) When deprived of carbohydrates, its preferred fuel, the body is forced to burn fats and protein for energy, thus causing
(B) When deprived of carbohydrates, which are the body’s preferred fuel, it is thus forced to burn fats and protein for energy, which causes
(C) When deprived of its preferred fuel, which are carbohydrates, the body is forced to burn fats and protein for energy, and thus causes
(D)The body is forced to burn fats and protein for energy when deprived of carbohydrates, its preferred fuel, which thus causes
(E) The body's preferred fuel is carbohydrates, and when deprived of them it is thus forced to burn fats and protein for energy, causing