Another reason to keep your sugar levels down is to consider the new evidence that links colon cancer to high glycemic index foods and low fiber foods in the diet. And a low glycemic diet is great to be skinny!
Foods that are low on the Glycemic Index: Here is a list http://www.the-gi-diet.org/lowgifoods/
Again, I will state that you should eat things like low fat cheese, low-carb protein bars, nuts, eggs, meat, low carb Greek Yogurt, vegetables, mostly citrus fruits and berries (two small portions a day), salads and lettuce mixes with low carb dressing. Anything else–only in moderation. If you need fiber, stick to nuts, seeds (especially flaxseed), fiber supplements and vegetables. Choosing fresh, non-starchy vegetables you can help increase your fiber intake while keeping your carb intake low. One cup of raw broccoli contains about 6 grams of total carbs, including 2.5 grams of fiber, and 1 cup of raw cauliflower provides about 5 grams of total carbs and 2 grams of fiber. Examples of other non-starchy vegetables include leafy greens, tomatoes, bell peppers and celery. You do not need to eat wheat to get fiber. Most cereals are high in sugar and carbs.
Skinny-Rules 