Stress increases production of adrenaline and cortisol both of which stimulate blood sugar release from stored glycogen. Are they overweight ? pancreatic enzyme insufficiency (rare) can play a role, also nutrient deficiencies - magnesium, zinc, chromium can play a role, as can a low soluble fiber diet, the diet may not be high carbs, but what carbs do they eat ? Carrots ? Beet Juice ? Grapes, Raisins, other dried fruit, fruit juices, alcohol ? some people are very sensitive to even healthy carbs/sugars. Eat healthy fats with carbs, small more frequent meals, eat slow release foods prickly pear fruit.flax seed, psyllium seed, chia seed, okra, and other “slimaceous" foods.