Been there - I think I'm a bit hypoglycemic.
Trying cutting down on sugars and carbs. Focus on eating healthy, unprocessed foods. Get lots of veges, some proteins and some carbs.
Also try eating several small meals throughout the day instead of one or two big ones - that'll help to keep your blood sugar more even.
Make sure to get a bit of protein and fruit at breakfast - it'll get you off to a decent start and help you to keep going.
Also - a bit of exercise throughout the day evens things out. Walking is great for this.
Good luck.
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Diagnosed Asperger's