While certain foods can trigger heartburn and acid reflux, also known as gastroesophageal reflux disease (GERD), eating large meals can also cause these conditions. Eating large meals puts pressure on the lower esophageal sphincter (LES) muscle, which is located at the bottom of the esophagus. The LES acts as a valve between the esophagus and stomach. It opens to allow food into the stomach and then closes to keep food and stomach acid from flowing back into the esophagus. When the LES weakens or relaxes abnormally, acid can flow back into the esophagus causing a burning pain in the chest, also known as heartburn.
Your stomach is only about the size of your fist, so eating a large plate of food can make the stomach expand and put pressure on the LES. This causes it to open and allow acid to reflux into your esophagus.
Being conscious of your portion sizes and slowing down when you eat can help prevent heartburn and acid reflux/GERD. Eating too fast makes it harder for your digestive system to perform the way it should. Having poor digestion increases your chance of experiencing heartburn. Occasional heartburn is not cause for concern and can usually be treated with lifestyle changes and over-the-counter medications such as antacids. However, if you have chronic acid reflux or heartburn, you may have a more serious condition, such as GERD.