Digestion is a complex process that requires coordination of physical and chemical factors. As you place food in your mouth and begin to chew, you are mechanically breaking it down and exposing it to digestive enzymes, releasing nutrients that will eventually be absorbed into your bloodstream. This multifaceted activity continues throughout the length of your digestive tract. Disruption of any of a number of digestive processes can cause bloating and nausea after eating.
Intolerance to a particular food can manifest as nausea, bloating, belching, excess gas and a change in bowel habits. Lactose intolerance – an inability to digest the sugar found in milk – is relatively common. Similarly, fatty foods, wheat, sugar and any number of foods can cause stomach upset for some people. Sometimes it helps to keep a food diary to zero in on specific foods that cause problems for you.
A hiatus hernia is a protrusion of a portion of your stomach through the hiatus -- the opening in your diaphragm leading from your chest to your abdominal cavity. A hiatus hernia sometimes causes bloating and nausea immediately following a meal. This condition is fairly common. At least 40 percent of people getting a chest x-rays are found to have it, according to "The Merck Manual for Health Care Professionals." Food sometimes "sticks" in a hiatus hernia, leading to a sensation of fullness or bloating.
Gastroparesis -- meaning paralyzed stomach -- is characterized by a reduction in your stomach’s normal churning motion, which is needed to mix and liquefy your food. Reduced stomach motion frequently results in a feeling of fullness, bloating and/or nausea after eating. Medications, surgery and diabetes are the most common causes of gastroparesis. A June 2008 review in "American Family Physician" reports that at least 10 percent of diabetics develop gastroparesis as a consequence of their disease.
Ulcers are erosions or "sores" in the lining of your stomach or the first part of your small intestine called the duodenum. Approximately 30 to 50 percent of stomach ulcers and up to 70 percent of duodenal ulcers in the United States are caused by infection with Helicobacter pylori. These spiral-shaped bacteria tunnel into the lining of your stomach and incite an inflammatory response that leads to an ulcer. Nonsteroidal antiinflammatory medications, such as aspirin and ibuprofen (Motrin, Advil), are also common causes of ulcers. While ulcers are classically associated with gnawing abdominal pain that is relieved by eating, bloating, nausea, heartburn and loss of appetite can also occur.
Pancreas and Gallbladder
Soon after you finish eating, your stomach begins releasing food into your duodenum, where it is mixed with digestive enzymes secreted from your pancreas, and bile released from your gallbladder. Malfunction in either of these organs -- due to gallstones or pancreatitis, for example -- results in alterations in the chemical makeup of the material in your duodenum. This triggers hormonal and nervous system reflexes that interrupt further release of food from your stomach. This digestive slowdown is experienced as bloating and nausea.
A variety of problems can lead to abdominal discomfort after a meal. Most of them are benign and easily diagnosed while others may require extensive investigation. In some cases, a change in your diet may be all that is necessary to relieve your symptoms. More serious conditions often require medical therapy.
In rare cases, a potentially life-threatening problem -- such as cancer -- can cause bloating and an upset stomach. Therefore, any persistent abdominal symptoms should prompt a visit to your doctor.