You are simply NOT digesting your food and the undigested food is rotting and causing methane gas to form and along with the undigested food becomes the "fart" that smells. Eating LOW fat, NON fat foods will cause gallbladder insufficiency and your fats will not be digested properly. Eating lots of carbs, low fat, is not a good diet. Carbs have quick, fleeting energy and will require you to eat frequent meals and this is not good for you. If you don't eat frequent meals when eating lots of carbs, you will get low blood sugar and not have the energy to function well.
That is simply not how our bodies were designed. The "smelly farts" should clue you in to how bad eating that way is for you.
Lactose intolerance is due to eating foods that do not contain bacteria to breakdown the lactose. Most people are lactose intolerant because they don't have good intestinal flora and eat and drink things like that terrible pasteurized dairy products derived from animals that eat GRAINS and put in feed lots. If you eat or drink dairy products that come from grass fed cows and is raw, you will not be lactose intolerant to them and actually become healthy from consuming those kinds of dairy.
Your pancreas sounds like it is insufficient and you are most likely suffering from LOW hydrochloric acid. This can be remedied easily with some nutrients and you will find you won't be farting anymore, or if you do, they won't smell.
good luck to you
CNT, B.A. biology & chemistry
advanced nutritional research