Because of her horrible diet, Irvine has anemia and vast nutrient deficiencies. Symptoms of anemia, a lack of healthy red blood cells, include dizziness and shortness of breath; this may be why Stacey collapsed.
The principle nutrients of chicken nuggets, the main component of all of Stacey Irvine's meals, are calories, fat, protein, carbohydrates, sodium, and cholesterol. Here is a breakdown of the nutrition of 9-piece McNuggets according the McDonalds themselves: