Vigorous exercise, especially soon after eating, can trigger nausea in even the fittest athletes. Being overheated and dehydrated makes you more susceptible to exercise-induced nausea. Because those who are obese are less able to cope with overheating, they may be more likely to experience heat-related illness and nausea during a workout.
Blood Flow During Exercise
When you exercise, your muscles need large amounts of oxygen. To supply sufficient oxygen, blood flow is shunted from your abdominal organs to your working muscles. Blood flow to the gastrointestinal tract can be reduced up to 80 percent during vigorous exercise, notes a 2011 review in "Journal of the International Society of Sports Nutrition." Blood is also diverted to your skin, helping your body dissipate the heat generated during a workout.
Nausea During Exercise
The reduction in blood flow to your gut during exercise can trigger nausea by disrupting junctions between the cells lining your digestive tract. This allows toxins produced by gut bacteria to enter the body, potentially leading to nausea and vomiting. Elevated core temperatures and dehydration add to the effect by further increasing the permeability of the gut lining. Eating before working out may worsen the nausea because exercise slows the emptying of your stomach.
Obesity and Heat Illness
Obesity can lead to overheating during exercise. People who are obese have a larger body mass in relation to skin surface than their leaner counterparts, making it more difficult to dissipate heat through sweating. People who are obese also produce more heat. A study published in "Medicine and Science in Sports and Exercise" in February 2009 compared the ability of normal weight and obese boys to acclimatize to exercising in the heat. The obese boys were less able to dissipate heat by sweating at the start of the study and took significantly longer to acclimate to the heat than did the normal weight boys.
While exercising can lead to gastrointestinal distress, that does not mean that obese people should avoid exercise. A study in October 2005 in "Clinical Gastroenterology and Hepatology" surveyed obese individuals about exercise habits and gastrointestinal distress. Although the researchers did not ask about nausea, they found those who exercised regularly were less likely to experience other gut problems, such as constipation, diarrhea and bloating. To reduce the risk of gastrointestinal distress, the American College of Sports Medicine recommends staying hydrated while exercising and avoiding foods high in fat or fiber before a workout.
- Journal of the International Society of Sports Nutrition: Food-Dependent, Exercise-Induced Gastrointestinal Distress
- The American Journal of Sports Medicine: Heat-Related Illness in Athletes
- Medicine and Science in Sports and Exercise: Responses of Lean and Obese Boys to Repeated Summer Exercise Heat Bouts
- Clinical Gastroenterology and Hepatology: The Association of Gastrointestinal Symptoms With Weight, Diet, and Exercise in Weight-Loss Program Participants
- Medicine and Science in Sports and Exercise: American College of Sports Medicine Position Stand. Nutrition and Athletic Performance
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