Allergies and Obesity: A Possible Link
Weight Watchers: Why do you think that allergies are an underappreciated explanation for the rise in obesity?
Leo Galland, MD: I’d say that a lot of clinicians who work with patients who have weight problems would probably agree that it’s harder for people to lose weight now than it was 30 years ago. Why? If you look at newer research like a 2015 study in Obesity Research & Clinical Practice, the authors acknowledge that there may be factors that are somehow affecting an increase in BMI over time beyond caloric and macronutrient intake, and physical activity. In that study, they suggest two allergy-related explanations. One is the increasing number of chemicals in the environment, some of which may disrupt metabolism — there’s a lot of data on the role of environmental chemicals in making people more allergic. And the other factor is change in the intestinal microbiome. Differences exist in gut microbiota between obese and non-obese individuals. So this study is really the first confirmation that losing weight is more difficult now than it was in the past for a variety of unknown reasons.
WW: How are allergies and obesity linked? This seems like a chicken-egg issue: Does obesity come first, causing allergy? Or does allergy come first, causing obesity?
LG: It’s definitely a vicious cycle. The laboratory data indicates an association between obesity and allergies, but of course, with all of these studies there can always be confounding variables. But in a word, it could be inflammation.
WW: Inflammation caused by … ?
LG: It breaks down like this: two kinds of cells and two chemicals. “Mast” cells and eosinophils, or eos, are called allergy effector cells. They are the main cells in the body that produce the symptoms of allergy. Mast cells, for example, contain most of the histamine in the body and so when you have an allergic reaction, the mast cells release all their histamine. That produces many of the symptoms that antihistamines block. But mast cells release about 200 other chemicals in addition to histamine. One of those is this substance called prostaglandin J-2, which can cause pain and inflammation.
Most people don’t know about prostaglandins, but drugs like aspirin and non-steroidal anti-inflammatory drugs block the synthesis of prostaglandins, which helps relieve pain and inflammation. Also, some allergy eye drops block prostaglandin synthesis in the eyes. Now, prostaglandin J-2 is a little-known prostaglandin that has been shown in laboratory studies to promote the growth of fat cells. That’s kind of interesting, but what makes it even more likely that this is clinically significant is that when researchers block the activity of mast cells in mice and rats, they don’t gain weight. So, there’s a lot we still don’t know, but mast cells – the principal allergy effector cells — may play a role in weight gain.
The other allergy effector cells are these eosinophils. While mast cells react immediately to allergens – producing swelling and itching — eos are involved in delayed reactions. They produce a lot of the ongoing tissue damage that happens with chronic allergies, because they secrete a bunch of chemicals that break down and damage tissues. So if you have eczema, for example, the late effect is thickened and scaly skin. That’s due to the damage produced by eosinophils. Also, eos can cause scarring of the lungs in asthmatics.
Now, this is the other side of the vicious cycle. One of the things that naturally controls the activity of eosinophils is a chemical called adiponectin. Adiponectin is a hormone-like substance produced by fat cells which has significant anti-inflammatory effects in the body. It may protect against the development of diabetes. And it has anti-allergic effects. The heavier you are the less effectively it’s produced, therefore researchers who work in the field of obesity-related diseases have theorized that it’s one of the reasons that obesity produces inflammation — and that weight loss is so helpful for so many different conditions — because weight loss may increase adiponectin production.
WW: So then you have less inflammation, and potentially less allergic reaction as well?
LG: Right. If adiponectin goes up, allergic reactions are better controlled, less severe, and you have less generalized inflammation. And people who start losing weight often experience metabolic and also immune system benefits pretty rapidly. It’s not as if you have to reach your ideal body weight in order for those benefits to occur.
WW: How can someone know if this is their problem?
LG: That’s the bigger question. And what do you do about it? There are several things to look at. The first is, do you have a hard time losing weight? You do the same things that your friends are doing, and your rate of weight loss just is not what theirs is. There’s this notion of ‘well, you have a slow metabolism.’ Why do you have a slow metabolism? That’s the first thing. The second thing is that you may see wide fluctuations in body weight with changes in diet. That is, you eat a particular way and you put on five pounds in a week, or you drop five pounds in a week. A lot of that weight change is not really due to fat. It’s due to fluid. And those kinds of fluid fluctuations are a clue that there may be a food allergy affecting your body.
The third thing is you have other symptoms like lethargy, joint or muscle pain or stiffness, headaches, digestive problems, itching anywhere, or congestion that may or may not be very troubling, but which are kind of there. A lot of people live with symptoms like this, and they don’t seek medical attention for them because they just kind of accept them. So if any of those three things are your characteristics, it’s worth exploring a role for food allergy.
WW: So this isn’t like seasonal allergies—this is strictly a food allergy situation?
LG: Not strictly. Some people may notice seasonal fluctuations, as well. It’s mostly a food allergy situation. There are no guarantees, of course, but once you get the allergy under control, you might be in a situation where you can start losing weight normally by doing smart things.
Leo Galland, MD is a New York City-based internist, integrative medicine specialist, and frequent contributor to Weight Watchers magazine. His new book, The Allergy Solution: Unlock the Surprising, Hidden Truth About Why You Are Sick and How to Get Well will be available in bookstores everywhere on May 10, 2016.