Foods that decrease metabolism are those that contain pesticides, often Genetic Modification, and nutrient deficiencies. I'm not a fan foods like Soy, it always caused me headaches or some sort of aches. Look on bottles of almost any processed foods, Soy or soy oil is a top ingredient touted as a superfood - I don't believe the hype. Goitrogenic foods can be problematic in high quantities, but I haven't experienced any problems with the majority of them as long as they are organic. Many goitrogens can be deactivated by heat however; at what levels, I don't know exactly.
I'm curious about your hypoglycemic issue, when did it start? Any important background details you can list? When you mentioned hypoglycemia, magnesium popped up immediately. It sounds like you might have deficiencies, multiple ones. One vitamin/mineral is never enough, they need to be balanced - not too high, not too low. I also wonder if you have some food-type allergies. How is your GI status?