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 an upset stomach 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, certain sugars and any number of other foods can cause stomach upset for some people. Sometimes it helps to keep a food diary to identify specific foods that cause digestive upset for you.
Delayed Stomach Emptying
Delayed stomach emptying, known medically as gastroparesis, refers to a reduction in your stomach’s normal churning motion, which is needed to mix and pulverize your food. Reduced stomach motion means that food stays in your stomach longer than normal, frequently resulting in a feeling of fullness, bloating and/or nausea after eating. Medications, surgery and diabetes are the most common causes of gastroparesis. A January 2011 "Clinical Gastroenterology and Hepatology" article reports that 5 to 12 percent of people with diabetes report symptoms of gastroparesis. The condition is more common in people with type 1 diabetes than in those with type 2.
Ulcers are erosions or sores in the lining of your stomach or the first part of your small intestine, called the duodenum. Helicobacter pylori bacteria are present in 95 percent of people with duodenal ulcers and 70 percent of those with stomach ulcers, note the authors of a February 2015 "American Family Physician" article. These spiral-shaped bacteria tunnel into the lining of your stomach or duodenum 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. 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. There 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 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, Professional Version." Although many people with a hiatus hernia do not experience symptoms, food sometimes "sticks" in the portion of the stomach bulging through the diaphragm, leading to a sensation of fullness or bloating.
A variety of problems can lead to abdominal discomfort after a meal. Most of them are not serious 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.
Reviewed by: Tina M. St. John, M.D.