Food intolerance is a digestive system response to food that irritates the system or that the system cannot process. Lactose intolerance is the most common, but almost any food can cause symptoms in a given individual. Food intolerance is common, and most people have had an adverse reaction to food at some time. It becomes a problem when the same food always causes symptoms for you. Food intolerance should not be confused with food allergy, which is an immune system response, or food poisoning, caused by spoiled or tainted food.
Symptoms of food intolerance vary with the individual, and perhaps with the episode. Symptoms include: nausea, stomach pain, gas, cramps, bloating, vomiting, heartburn, diarrhea, headaches and irritability. These are the common symptoms, but some people may have other, similar symptoms. Of the common symptoms, the only one that would seem to result in weight gain would be bloating. Other symptoms, by interfering with digestion, could result in temporary weight loss. See a doctor if your symptoms are severe or frequent.
Weight Gain Theories
Although there is no proof that food intolerance can cause weight gain, there are some theories on the subject. One theory is that food intolerance slows metabolism and thus causes weight gain. Another is that people crave foods to which they are intolerant, and withdrawal leads to binge eating. A third is that dealing with processing food while intolerant drains energy, so that the individual becomes sedentary, leading to weight gain. Theories centering on immune response are unlikely to be valid, as food intolerance does not come from the immune system.
Is It an Allergy?
Food allergies are an immune system response to food to which you are allergic. Common allergens are peanuts, tree nuts, fish, shellfish, milk, eggs, soy and wheat. In the U.S., 4 to 5 percent of the population is thought to have food allergies. Symptoms can be mild to so severe they require emergency treatment. They include: rash or hives, nausea, stomach pain, diarrhea, itchy skin, shortness of breath, chest pain, swelling of airway and anaphylaxis. Reactions can be immediate and can be caused by a small amount of the food. You have to avoid these foods. A food allergy will not cause weight gain.
Identifying Cause of Food Intolerance
Tests used for allergies, such as blood tests, skin prick, or muscle testing, do not work for identifying the causes of food intolerance. The best test for food intolerance is an elimination diet. Keep a food diary for a few weeks, noting when you have symptoms of food intolerance and what you ate during the day or two before. Get guidance from a dietitian if necessary. Eliminate suspect foods from your diet, then reintroduce them gradually, one every two weeks. You should be able to tell which foods make you sick. Stop eating these, and you will not have to worry about their effect on your weight.