It puts a load on your digestive system. She claims that, of the three macronutrients, fat is the slowest to digest, requiring enzymes and digestive fluids such as bile and stomach acid to break it down. When you add fat to your diet, your digestive system will work overtime, resulting in bloating, nausea, and pain. However, the oil itself won't cause any problems; it's what comes out of your body after digestion that can cause issues. The food you eat is converted into energy for your body. Some of this energy is used right away while some is stored for future use. All foods contain some amount of sugar (simple carbohydrates) which is used by your body as an energy source. After eating your meal, there is still some residue left over from before digestion starts. This material is called "undigested carbohydrates". They are easily absorbed into your bloodstream and provide you with a quick rush of energy - but also cause blood sugars to rise and fall rapidly. Over time this can have negative effects on your health. Fiber is found in vegetables and fruits and helps move material through your digestive system and prevent constipation. The remaining parts of your meal are then passed out of your body in stools (faeces). Stool size is affected by how much fiber you eat. If you tend to have large amounts of fruit and vegetables in your diet, you'll be passing out smaller amounts of material per stool than someone who eats less fiber. Now, back to fat.