This may be a general question, but may also end up being a "Dear Mark":

First, some background information:

I am a 22-year old female, 5'8" tall, weighing 105 pounds. I have not confirmed this, but would estimate my body fat % to be in the single digits, or at least very low teens (as in: my current degree of "lean"-ness would make me an excellent resource for an anatomy class).
I have always been naturally slim, with my highest weight hovering around 128 (about 5 years ago). However, due to internal and external pressures and influences, as well as perfectionist tendencies, I developed an unhealthy relationship with food, eventually descending into all-out ortho-/anorexia/perpetual over-excercising. These tendencies, coupled with a year-long stint as a vegan (and a low-carb, low-fat vegan, at that), resulted in dramatic, rapid weight loss (and amenorrhea, and hair loss, and the whole nine yards).

I finally jumped off the vegan train about two months ago, reintroducing fish and seafood, yogurt, and eggs into my diet. I already feel a great deal better. I have continued to be active, because my intuition tells me that turning into an over-eating couch potato would not necessarily result in a return to a healthy state.

However, my intuition has also been tremendously tricky when it comes to appetite. For example, I can count multiple days over the past few weeks that were full of various physical activities, but during which I consumed 1600 calories or less. For example, yesterday was such a "very physical" day: roughly 2 hours bicycling (to and from work, home, etc, at a fairly vigorous pace, over bridges and the like), a vigorous early-morning yoga class, and aerial acrobatic practice in the evening, in addition to basic daily activities. However, I had very little appetite.

In such situations, is it more important to "listen to the body", or should I muscle through and force myself to eat, regardless of what my intuition and stomach are telling me? It seems (literally) counter-intuitive to force anything, in either direction, but intellectually, it would make sense to eat regardless of the absence of physical hunger.

Any thoughts or suggestions would be greatly appreciated!