Stress eating.

 I am raising my autistic grandson. Every time he starts having a tantrum, I start stuffing my face. I have already gained back 30 of the 100 lbs I have lost.

You have my compassion.  My nephew is autistic and I know what a challenge it can be.  The fact that he is your grandson and you are stepping up is commendable.

I hope you are getting some respite care.  Check with children's services or other organizations.  This is not something that you can deal with alone.  I think maybe some more support and help may help you cope better without overeating.

Please ask for and accept help if you can.  This is not a burden that can be carried alone.  Your grandson needs you to be healthy and strong for him and the only way you can do that is by taking care of yourself.

My heart goes out to you.  You are a wonderful grandmother to take care of him as you are.

I agree with Ladytazz, check into any assistance that you might be able to obtain.  It is a full time job physically but even more emotionally.  Check into any local or state children's services that you can get.  

As a care provider, you're giving your all to him and nurturing yourself by overeating.  Completely understandable.  Check into an autism support group or counselor to learn about ways to handle tantrums and other behaviors.  Learn what you can do for him during these episodes AND for yourself as to how to handle them without eating.

I searched for some links that might be helpful.  They are:

National Autism Association:  http://nationalautismassociation.org/

I don't know where you live but this is a link for "autism kids services" that may help:
https://www.google.com/?gws_rd=ssl#q=autism+services+for+kids&revid=626980479

Autism Services Group:  http://www.autismservicesgroup.com/

Autism Home Support:  http://autismhomesupport.com/

Please continue to post so we can support you.  

I chew gum when I get stressed some times.  I don't eat at work, so thats not an option for me but the gum does help.