Have you ever eaten something and noticed that you could feel mucus forming at the back of your throat? And the next thing you knew, you were “ahem”-ing and coughing to clear your throat? Perhaps you get gas, bloating or headaches after eating certain foods. Not everyone has the same signs or level of sensitivity, but over time, eating foods that you are sensitive to can lead to a whole host of problems and one of them is difficulty losing weight.
Many people might not realize that food sensitivities could be the reason for weight gain or the culprit behind losing the battle of the bulge, but Dr. John Mansfield, a pioneer in the field of allergy and nutrition, states that if the body is aggravated by a food it can cause sensitivity and weight gain. In his book, The Six Secrets of Successful Weight Loss , Dr. Mansfield declares that food sensitivities are "by far the commonest single cause of weight gain," rather than too many calories or a lack of exercise.
The theory is that an allergic-type reaction caused by food sensitivities disrupts a feedback mechanism in the brain. After eating, the hypothalamus receives signals from the gut that stored body fat has increased, prompting us to feel less hungry. "When this mechanism is working well, your body weight remains constant, despite quite widely varying calorie consumption from day to day," says Dr. Mansfield. "However, the adverse reaction caused by regularly eating foods you are sensitive to causes the constant level of weight to be permanently set at an incorrect, higher level. This is why you can't shed the pounds regardless of what you eat." 
Knowledge of this fact can change the way you eat, and therefore change your life, so let’s look a bit closer at food sensitivities and what you can do about it. Some sensitivities and allergies are fast-acting and can be detected early because of symptoms such as hives or rashes, but others are often unknown because they mimic everyday conditions such as headaches, fluid retention, gas, and could even be mistaken for irritable bowel syndrome. To make matters even more complicated, some symptoms may take days to appear after eating the trigger food.
Read more about irritable bowel syndrome
Here are some of the most common foods that can cause reactions as well as where they may be hidden:
Also known as: wheat bran/flour/germ/starch, durum, emmer, farina, farro, kamut, seitan, semolina and spelt. Some people may be sensitive to gluten as well and additional grains containing gluten including barley, rye and triticale.
Some possible sources: breads, baked goods, pasta, cereal, crackers, gravy mixes, croutons, creamed soups, and battered foods.
Also known as: casein, caseinate, lactoferrin, lactoglobulin, whey, and curds.Some possible sources: cheese, cream, sour cream, butter, ice cream, yogurt, baked goods, coffee, chocolate, brown sugar, fried foods, seasonings, and soup mixes.
Also known as: crustaceans like crab, shrimp, lobster; shellfish such as clam, scallops, squid; and some people are even sensitive to a specific fish such as salmon, bass, sole or snapper.Some possible sources: deli meats, hot dogs, pizza toppings, salad dressings, sauces (marinara or Worcestershire), and marshmallows.
Also known as: arachide, beer nuts, ground nuts, and nut meats.Some possible sources: cakes, cookies, fried foods, Szechwan sauce, vegetarian meat substitutes, and cereals.
5. Tree Nuts
Also known as: Almonds, Brazil nuts, cashews, hazelnuts (filberts), macadamia nuts, pecans, pine nuts (pignolias), pistachio nuts and walnuts. Anacardium nuts, nut meats, and pinon.Some possible sources: baked goods, salads, chocolate bars, trail mix, flavored coffee, and Amaretto.
Also known as: ovo, albumin, meringue, vitellin, and conalbumin.Some possible sources: sauces, baby food, icing, pies, cakes and other baked goods, quiche, and pasta.
7. Colors and Dyes
Also known as: FCF – This stands for "For Coloring Food”. (Take caution with any dye but especially
dyes with a number in it such as FD&C Red Number 4 as this
indicates that it’s likely synthetic.)Some possible sources: candy, juices, baked goods, salads, chocolate bars, trail mix, flavored coffee, and supplements.
Also known as: soya, soja, soybean, soyabeans, soy lecithin, edamame, kinako, and okara.Some possible sources: tofu, tempeh, miso, natto, chewing gum, hot chocolate, baby formula, baked goods, canned tuna, candy and chocolate.
Also known as: Potassium bisulphate/metabisulphite, sulfur dioxide, sulfurous acid, sulfiting agents, E 220, and E 221.Some possible sources: packaged foods, wine and beer. 
1. Try an elimination diet for 3 weeks. Cut out the most common food allergens as per the list above and any other food you suspect you may be sensitive to.
3. Take probiotics daily to boost the healthy bacteria in your gut. Look for brands that contain a high culture count and multiple strains of bifidobacteria and lactobacillus. Choose from reputable brands that have a delivery system to ensure that the live probiotics survive through stomach acid. 
Read more about preventing peanut allergies in babies by eating peanuts
When you eliminate the foods you are sensitive to you will start to feel better. Your energy will increase, your symptoms will disappear and with a bit of exercise and proper diet your weight issues will be a thing of the past. As Dr. Hyman says, “If you want to get rid of your gut, you have to fix your gut.”
[Editor's Note: If you want to eliminate unhealthy ingredients and chemical additives from your diet for good, click here to sign up for a Naturally Savvy Get Healthy Challenge.]
Image: Basileia Gorgo
 Hodgekiss, A. (2012). Food sensitivity could be stopping you lose weight, says doctor who also claims low-fat diets can make you HEAVIER. http://www.dailymail.co.uk/health/article-2216110/Diet-working-A-food-intolerance-slowing-metabolism-says-leading-doctor-claims-low-fat-diets-CAUSE-weight-gain.html.
 Robertson, A. Canada's 9 Most Common Food Allergies. http://www.canadianliving.com/health/prevention/canadas_9_most_common_food_allergies.php.
 Hyman, M . (2012). How Hidden Food Sensitivities Make You Fat. http://drhyman.com/blog/2012/02/22/how-hidden-food-sensitivities-make-you-fat/.