Talked to my nutritionist yesterday

I had a different surgery, some kind of combo , an open abdominal, it included a RNY modification and multiple other procedures including banding above and below the pouch, removal of all but two feet of my colon. (10 procedures in a four hour surgery)   My lab values tend to the lower side of normal..except my Iron which is always low...So, I do not have  the typical absorbtion, neither do I have the ability to swallow most vitamins, due to sizing.. Can't keep the liquids down either...they return.I have to fight to get calcium, zinc, magnesium in, and use mostly foods to boost these...I use home made bone broth and smaller sized pills alternating.(It is not pleasant to have 'the sensation of something hung' at the base of your esophagus.)

   I use a B complex sublingual,on a semi-regular basis..(for me,normal use is 2 or three times weekly, depending on my  intake).You would need more than the B-12levels, a complete panels of the B complex would be in order. I don't know what component of the B complex it is that helps the cravings,..it has 5 different B's in it... but it does work for me. It does take three days.

I  use my cravings for a monitor...if I am craving, something is out of balance.(For me, it is something in the B-complex..and may be due to the extensive colon resection. )

Your Key will be to FIND the issue that is out of balance for YOU.It could be another form of B, or another vitamin. You may need to try different things. Labs may not give the complete picture, but could assist you with your search.(B 12 is normal so it's probably not B-12.) Sounds like you are having labs done regularly, and a diet diary could help pinpoint the essential you are missing...Congratulations..you have eliminated one thing...  Something to consider... Have you tried sprouting, to boost the other B's naturally?..  Natural or non-chemically made suppliments do not become toxic according to the physician reports I receive,(..Mercola and others)

 You must be pro-active, expect no on else, on your health care team, to be as concerned as you re: this issue....  Ask yourself, keep a diary...to answer these questions for yourself ...Is there one food that you are craving? and what essential is it high in? (if one craves liver or raisins, could be iron..) 

   Keep in mind that a 'low normal" for a lab value, might not be YOUR normal. I found this with my potassium level,It is a symptom.. of lower potassium and low magnesium. if my K+, in low normal range I have severe cramps..and boost magnesium, calcium, zinc and potassium to have a cramp free night.

This is just one place to start.  Hope this helps to understand the method I use and will help you trouble shoot any future problems.

Like most others have said, you shouldn't experiment with starchy vegetables until you have some experience with maintenance under your belt. Per chance, was she trying to say that you need to eat more carbs? Because you can get carbs with other veggies, dairy, fruit, beans, etc. Unfortunately, most people find that excess of carbs equate to excess hunger, thus weight gain.