QUOTE(LoveMeNot @ Nov 8 2013, 08:51 AM)
I know I can eat. Unfortunately it's so hard for me to resist those unhealthy yummy food. but I'm trying really hard now to replace it with good ones e.g. salad. If only I can just switch off the urge. Is there medication or something to suppress the appetite huh?

Hmm, it's a mental game. Notwithstanding that, you're probably addicted to sugar (yes there is such a thing). It's just like cigarettes, you'll probably feel bad trying to remove it. How I dealt with it: changed my taste buds to love healthy foods such as greens, salads, roasted chicken, sour yogurt, etc.
How it works:
1. Once you start eating these first (just take the first mental leap!), you won't have much space or appetite for extras anyway.
2. Knowing that sugar is bad stuff, it'll slowly set in mentally to try to avoid it. In the medium term, once your taste buds have become accustomed to blander, more natural taste of foodstuff, any sweet things that touches your tongue will be quite pronounced (you'll feel a slight dislike).
I wished I had your appetite though! Having good appetite is a very good thing. Use it to your advantage!