Eating too much gives an overfull stomach. The stomach has to do its thing before it can pass food on to the intestines, so there's a necessary delay. When there's too much food, the squeezing motions of the stomach encourages acid reflux, which gives you heartburn. If you're eating fruit right after a fatty meal, that can give you heartburn and lots of gas. Fatty foods need more time in the digestive system, so eating fruit after fat means that the fruit remains in the stomach so long it starts to ferment.
Most people order a soda or pop to go with their fatty junk or fast food.
This makes the problem worse because the carbonated drinks promote bloating and gas. Caffeinated drinks can elevate stomach acid levels over that which is required, so there's a volcano like effect with the acid. Remember not to drink more than one average-sized glass of fluid during a meal since this dilutes stomach acid and the digestive enzymes. Try to have relaxing meal times. Stress, anxiety and rushed meals impairs digestions because stress hormones change normal digestive actions.