1-2 day fast being skinnier, raw food and calorie amount questions.

So a quick few questions for y'all :)

I am 5'9.5 at around 138 lbs. I'm a pretty skinny guy, but ever since starting to eat 100% raw foods (my daily diet is a few avocados, 1-2 green smoothies with spinach and a bit of kale, soaked sunflower seeds, apples, mango, a lot of bananas, and other various fruits) I've needed to eat almost 3000kcal to maintain my weight. Before raw, I was eating around 2300 to maintain 140. I realize that it's not so much HOW MUCH you eat, but WHAT YOUR BODY ASSIMILATES that matters. Any idea why this increase in food is needed... and also, would doing a 1-2 day juice fast with celery/apple juice make me lose too much weight? I am thin but not THAT thin... but my weight is driving my mom and dad crazy for some reason. They will not let me stop hearing about it (I'm a 23 yr old college student, btw)

Thanks for any and all help :)