Gastroesophageal Reflux Disease (GERD): This is the most likely diagnosis due to the common presentation of nausea and indigestion, which are typical symptoms of GERD. The condition is prevalent and often associated with dietary factors, obesity, and lifestyle.

Functional Dyspepsia: This condition is characterized by recurring symptoms of indigestion that are not explained by other pathologic conditions. It's a common cause of nausea and indigestion and can be related to stress, eating habits, or sensitivity to certain foods.
Peptic Ulcer Disease: Although less common than GERD or functional dyspepsia, peptic ulcers can cause nausea and indigestion, especially if they are located in the stomach or the duodenum.
Irritable Bowel Syndrome (IBS): While primarily known for causing abdominal pain, bloating, and changes in bowel habits, some patients with IBS may also experience nausea and indigestion.

Gastric Cancer: Although rare, gastric cancer can present with nonspecific symptoms such as nausea and indigestion. It's crucial to consider this diagnosis, especially in older adults or those with risk factors like a family history of gastric cancer or Helicobacter pylori infection.
Pancreatic Cancer: Similar to gastric cancer, pancreatic cancer can have a nonspecific presentation, including nausea and indigestion, particularly if the tumor is located in the head of the pancreas and causes obstruction of the bile duct.
Myocardial Infarction: In some cases, especially in women, diabetes, or the elderly, a heart attack can present atypically with symptoms of nausea and indigestion rather than the classic chest pain.

Zollinger-Ellison Syndrome: A rare disorder characterized by excessive gastric acid production due to a gastrin-secreting tumor, leading to severe peptic ulcers, diarrhea, and abdominal pain.
Eosinophilic Esophagitis: An inflammatory condition of the esophagus that can cause nausea, indigestion, and difficulty swallowing, often associated with food allergies or atopic diseases.
Gastroparesis: A condition where the stomach takes too long to empty its contents, which can cause nausea, vomiting, and indigestion, often seen in diabetes, after certain surgeries, or due to neurological disorders.