Secret sources. (updates).

People who want to lose weight may in fact sabotage their chance of success by eating foods they believe to be better for them, thanks to hidden wheat and dairy products in many foods. Worse, people who are allergic to wheat or dairy products run the risk of serious health problems if they mistakenly eat foods they think are safe.

"Common foods like wheat and dairy cause many people to eat more if their bodies don't metabolize wheat and dairy properly," or they cause an allergic reaction in some people, says Carol Fenster, PhD, author of several wheat-free, gluten-free cookbooks and someone who is gluten-free herself. The result is an imbalance in the body, which triggers cravings and excess fat storage.

Fenster says some of the unlikely places wheat turns up are in cream of mushroom soup and low-fat sour cream. Wheat is added to each as a thickener. "When they take out the fat, they have to have some way of putting back all the substance or else the sour cream will be runny," Fenster says. Adding wheat thickens the sour cream to its full-fat consistency.

Casein, a milk protein, is often added to dairy-free cheeses to make them melt more evenly and taste better, Fenster says. That may surprise people who avoid dairy products and buy cheeses made from soy or rice. Casein also turns up in low-salt or salt-free canned tuna, though Fenster says she has no idea why it would be there.

Pharmaceutical companies often use lactose as a filler, but Fenster says that's not as much of an issue with products sold through natural products retailers.

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