Do Food Allergies Make You Fat?

by Michelle Fiscus. 0 Comments

Do food allergies make you fat?  That’s a great question and the answer depends on who you ask.

The theory goes: a specific food allergy or allergies prevents someone from losing weight and causes all sorts of awful symptoms.  Diet plans based on this call for dropping a certain food (or in some cases foods) -- so you can lose the weight once and for all.

It’s incorrect to say food allergies are making you fat.  Technically it’s not a food allergy.  It’s food intolerance in question.  Here a few medical definitions you need to know:

A food allergy is an abnormal response to a food triggered by the body’s immune system. When the body has an adverse reaction to food it produces an antibody called immunoglobulin E (IgE). There are several types of immune responses to allergens. The response may be mild like a rash or (in rare cases) it can be associated with a life threatening reaction called anaphylaxis.

A food intolerance causes a wide variety of symptoms: everything from bloating, to headaches, and indigestion, but it is not a food allergy.  It is not life threatening. You can have a food intolerance to lactose-- which is the sugar found in milk and milk products, an intolerance to food additives, or an intolerance to gluten (which is not the same as actually having Celiac disease).  That is not an extensive list of culprits, but the food items that get the most complaints.

From this point forward, I am going to use the correct term: food intolerance.  But realize proponents of elimination diet plans often use the incorrect term: food allergy.  They are not synonymous and you are being misled when they use it.

There is no way to trace back the mainstream popularity of diet plans based on the concept of food intolerances, but Dr. Mark Hyman made a contribution.  He believes the wrong foods make you inflamed, and then the inflammation causes obesity. He even appeared on the Dr. Oz show, where he received support and endorsement for his theories. More recently someone named JJ Virgin wrote a book and diet plan about food intolerances. Her beliefs and diet recommendations are very similar to Dr. Mark Hyman.  She advocates dropping eggs, dairy, gluten, soy, peanuts, corn, and yeast for a period of at least 21 days.

Dr. Hyman cites two studies from 2007: one in humans and one in mice. You can’t make conclusions about human health based on animal studies. According to the British Medical Journal, “[Animal Studies] are generally of poor quality and lack agreement with clinical trials, which limits their usefulness to human health. This discordance may be due to bias, random error, or the failure of animal models to adequately represent clinical disease.”

Dr. Hyman’s evidence in humans comes from a study of children who were already overweight.  He claims their blood work showed high inflammation, whereas normal weight children did not, making the connection that inflammation causes obesity. Scientists really don’t know what happens in humans. And, there is plenty of research that shows those inflammatory molecules might be produced after someone becomes obese, in response to becoming obese—not before.

In the September 2013 edition of the Journal of Endocrinology, researchers admitted that, “Whether obesity precedes insulin resistance or vice versa is however still a matter of debate. Weight loss is particularly important in improving NAFLD [Non-alcoholic fatty liver disease] but also glucose metabolism and cardiovascular risk (Musso et al. 2012). Notably, patients with type 2 diabetes and NAFLD have shown that moderate weight reduction (about 8 kg) was sufficient to improve NAFLD and reverse hepatic insulin resistance (Petersen et al. 2005).”

A 2006 study that looked at the relationship between obesity, insulin resistance and inflammation talks about the same inflammatory molecules as Dr. Hyman; however those researchers suggest obesity causes those inflammatory molecules to respond, “In obesity, [white adipose tissue] is characterized by an increased production and secretion of a wide range of inflammatory molecules including TNF-alpha (TNFa) and interleukin-6 (IL-6).” The researchers are careful to admit there are no definitive answers, “[TNF-a’s] actual involvement in glucose metabolism disorders in humans remains controversial. IL-6 production by human adipose tissue increases during obesity. “

To make things even more confusing, IL-6 is also released during exercise and may serve a beneficial role in insulin sensitivity.

The point is, no one actually knows.

What we do know is there is a link between obesity and low grade inflammation. We do not know which comes first.  Just as Dr. Mark Hyman believes a bacterial toxin latches onto immune cells and creates inflammatory molecules which cause insulin resistance, it’s just as easy to hypothesize that first comes obesity, then comes insulin resistance, and then inflammatory cytokines are released in response to the insulin resistance.  

Besides the lack of scientific evidence in favor elimination diets, there is no way proven way to test for food intolerances that might make someone “inflamed”.

Immuglobulin E testing is used to diagnose food allergies.  If your body has an immune reaction to a food or substance, your body sees that item as an invader and will produce IgE in defense.  The body causes the symptoms associated with food allergies as part of that defense.

Doctors who believe in food inflammation use something called immuglobulin G (IgG) testing. The test is also looking for an immune reaction in the body.  Proponents of IgG testing say a positive test indicates your body has intolerance to a certain food. 

A larger portion of the medical community believes the presence of IgG actually indicates your body’s tolerance to the food, not intolerance. Canada does not support it for the purpose of food intolerance testing.

“There is no body of research that supports the use of this test to diagnose adverse reactions to food or to predict future adverse reactions. The literature currently suggests that the presence of specific IgG to food is a marker of exposure and tolerance to food, as seen in those participating in oral immunotherapy studies. Hence, positive test results for food-specific IgG are to be expected in normal, healthy adults and children. Furthermore, the inappropriate use of this test only increases the likelihood of false diagnoses being made, resulting in unnecessary dietary restrictions and decreased quality of life…. The CSACI strongly discourages the practice of food-specific IgG testing for the purposes of identifying or predicting adverse reactions to food. We also wish to remind the medical community that blood testing of any kind cannot substitute for consultation with a trained and accredited medical professional such as an Allergist/Immunologist for the diagnosis and management of adverse reactions to food.”

Plus, IgG testing can be expensive and is often not covered by insurance.

The medical community in the United States does not have a position on IgG testing.  However, Science Based Medicine  (a site written by and edited by medical doctors) drew their own conclusions after looking at the scientific evidence:

“IgG antibodies signify exposure to products—not allergy. IgG may actually be a marker for food tolerance, not intolerance, some research suggests:

Children with eczema and egg or milk allergies with higher levels of IgG to milk/egg were more likely to be tolerant of these foods at a later age. Resolution of cow’s milk allergy is associated with increasing IgG A study found increasing IgG in patients who underwent oral immunotherapy for milk or peanut allergy. 

That research is continuing. But given the lack of correlation between the presence of IgG and physical manifestations of illness, IgG testing is considered unproven as a diagnostic agent as the results lack clinical utility as a tool for dietary modification or food elimination.”

So why do people lose weight on elimination diets if IGg testing actually indicates a tolerance to foods and not an intolerance?

Let’s take a look at JJ Virgin’s plan again.  What are you left with when you drop all of her foods: eggs, dairy, soy, yeast, peanuts, corn, gluten? Basically you can eat meat, vegetables, fruits, and nuts.  That’s pretty close to the paleo diet, which has its own critics.  You can’t eat anything processed because many of those seven items are in a lot of packaged foods.  Of course you are going to lose weight.  It is very low carb by nature. It is difficult to over eat those items unless you take a spoon to a jar of almond butter. When you lose weight you experience all those wonderful effects she touts in her book because weight loss in general causes positive changes.  Even a 10% reduction in weight causes a dramatic change in your body, regardless of how you lose that weight.

There is no correlation proving eliminating these foods causes weight loss because your body never tolerated those foods.  In eliminating them you are automatically reducing your food choices and are forced to eat a low calorie and low carb.

There are a few medical circumstances when you should eliminate foods and those include:

If you have an allergy to a food (like peanuts) that causes an IgE mediated reaction. If you have an allergy to dairy or medically diagnosed lactose intolerance avoid it or choose lactose free dairy. If you have medically diagnosed gluten intolerance or Celiac Disease, avoid gluten.

This is not the end of the story on food intolerances. Scientists don’t have all the answers.  As new research becomes available in favor of either side of this issue, I’ll be sure to update this story so you get the truth. For questions regarding the information contained in this article, email the author at


Michelle Fiscus writes a regular column for Michelle and her husband own a personal training and nutrition business based in Frederick County and hold industry certifications and credentials. 

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