More attention is focused on food allergies these days because they’re increasing in frequency. Why food allergies and all allergies are more common than they used to be is unclear. Scientists point to the fact that we live in a more sterile environment these days as a factor. Research shows that when babies and children are exposed to potential allergens early in life, they’re less likely to develop allergies. For example, when children have pets early in life, their risk of allergy is lower.
Allergies are certainly inconvenient, especially if you’re allergic to a number of foods. There are even claims that food allergies are linked with weight gain. Is there any truth to this idea?
Food Allergies versus Food Intolerances
First, let’s look at what a true food allergy is. Many people confuse food allergies with food intolerances. The two entities are quite different. Only about 4% of adults have true food allergies but almost one-third have one or more food intolerances.
True food allergies involve an overreaction of the immune system. Specifically, your immune system has preformed antibodies, specifically IgE antibodies, against a particular food. When you eat that food, your immune system is activated and cells release chemicals like histamine that cause a host of unpleasant symptoms like an itchy rash, swelling in the hands or feet, sensation of throat tightness, and anxiety. In severe cases, you might have a drop in blood pressure, problems breathing or even death when you eat a food you’re allergic too.
With a true food allergy, the reaction usually comes on quickly after eating certain foods, often within minutes. The most common foods responsible for food allergies are shellfish, fish, peanuts, tree nuts, soy, wheat, egg, and milk.
If you have a food intolerance, you won’t typically have dramatic, life-threatening symptoms and the symptoms you do have don’t usually appear right after you eat the offending food. Usually, the symptoms take an hour or up to 12 hours to develop and are digestive in nature. Typical symptoms of food intolerances include nausea, bloating, abdominal cramping, diarrhea, or headaches. Food intolerances are more common than food allergies and may be caused by a deficiency in an enzyme required to break down food.
For example, people with lactose intolerance can’t tolerate dairy products because they don’t have enough lactase, the enzyme that breaks down milk sugar. When people are intolerant of lactose consume dairy products, they experience abdominal cramping, diarrhea, and nausea. Lactose intolerant individuals often say they’re “allergic” to milk when they simply don’t have enough of the enzyme needed to digest lactose. Other people have a true milk allergy and can experience severe, even life-threatening symptoms when they drink it.
Some people appear to be sensitive to certain food additives in processed foods, especially sulfites, nitrates, and monosodium glutamate, or MSG. As you’re probably aware, a significant number of people are sensitive to gluten yet don’t have celiac disease, but they develop digestive issues when they eat gluten-containing foods.
Foods like cabbage, onions, and beans are difficult for some people to digest and commonly cause symptoms of food intolerance, including gas, bloating, and nausea. Salicylates in some fruits, herbs, and vegetables, especially tomato sauce and citrus fruits, are another compound strongly linked with food intolerance.
Food Allergies and Weight Gain
What about the issue of weight gain? True food allergies, those caused by an immune reaction, would be unlikely candidates for weight gain since people who are truly allergic to a certain food, by necessity, avoid it.
What about non-immune food intolerances? If you ask most doctors whether food intolerances, not related to the immune system, are linked with weight gain and they’ll probably tell you no, but there are some health practitioners who believe otherwise.
According to Dr. Mark Fuhrman, the head of functional medicine at the Cleveland Clinic, food intolerances may cause gut inflammation, which can, in turn, may contribute to obesity by fueling insulin resistance. As he points out, when you eat a food you’re intolerant of, it can potentially damage the thin lining of your gut causing it to be become “leaky.”
Leakage of proteins and food particles from the gut into the bloodstream can elicit an immune reaction and inflammation. In this way, food intolerances may elicit a low-grade immune response that we know of as inflammation, which may in turn fuel insulin resistance.
Do You Have a Food Allergy or Intolerance?
To find out if you have a true food allergy, an allergist can do a skin test or blood test to see if you have antibodies against certain foods, although these tests aren’t always accurate. In fact, they can produce false-positive results, indicating that you’re allergic to a food when you’re not.
A more accurate test an allergist can do in their office is a “food challenge,” where they give you a food they suspect you’re allergic to under controlled circumstances and see how you respond. If you get this test, make sure an allergist does it in a medical setting where equipment is available should you experience a severe reaction. This is one of the most accurate tests for true food allergies.
To find out if you have a food intolerance, as opposed to a true allergy, will take a little detective work. Most doctors recommend an elimination diet where you eliminate the most common foods that cause food intolerances from your diet for at least 3 weeks and slowly add them back in while monitoring your symptoms. If you experience symptoms when you add a food back in, that’s a food you should keep out of your diet. If you lose weight when you stop eating that food, so much the better. There’s little research to support the idea that food intolerances cause weight gain at this point, but it hasn’t been well studied either.
The Bottom Line
True food allergies are unlikely to cause weight gain because most people are forced to avoid the foods they’re allergic to due to the severe nature of the symptoms. It’s less clear-cut whether food intolerances cause weight gain by their association with low-grade intestinal inflammation and insulin resistance. Either way, if you’re experiencing digestive symptoms you think could be a food intolerance, it’s a good idea to get allergy testing and do an elimination diet to see if your symptoms improve. At the very least, eating foods you’re intolerant of places extra stress on your digestive system and should be avoided.
References:
Dr. Mark Hyman. “Are Your Food Allergies Making You Fat?”
WebMD. “Food Allergies: 5 Myths Debunked”
J Investig Allergol Clin Immunol. 2007;17(5):302-8
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