Anyone who checks blood sugars after meals ("postprandial") already knows that there are hidden sources of sugar in many common foods.
You hopefully already know that foods like breakfast cereals, breads, bagels, pretzels, and crackers cause blood sugar to skyrocket after you eat them. They are all carbohydrates. Carbohydrates increase blood sugar, often substantially. Blood sugar levels in non-diabetics of 120, 140, 150 mg/dl or higher are not uncommon. Blood sugar this high add to risk for heart disease. They also damage pancreatic cells that make insulin, pushing you closer to diabetes (a process called "glucose toxicity").
But sometimes you eat something you thought was safe only to find you're showing blood sugars of 120, 130, 150+ mg/dl.
Where can you find such "stealth" sources of sugars that send postprandial blood sugars into the stratosphere, along with small LDL, inflammation, blood pressure, and cause you to grow visceral fat?
Here are a few such hidden sources:
Many commercially-prepared balsamic vinaigrettes, especially the "light" varieties, have 3 or more grams carbohydrates per tablespoon. Generous use of a sugar-added vinaigrette can therefore provide 12+ grams carbs. (Some, like Emeril's and Wish Bone, also contain high-fructose corn syrup.)
I learned this lesson the hard way by taking my blood sugar after having a hamburger, turkey burger, or vegetarian burger (without bun) at restaurants: blood sugar would go way up. The effect is due to bread crumbs added to the meat or soy. Topping with ketchup can only make it worse, adding another eight grams sugar per two tablespoons in the form of high-fructose corn syrup, corn syrup and/or sucrose.
If it were just tomatoes, it would still be somewhat high in sugars. But commercially-prepared tomato soup often contains added high-fructose corn syrup, sucrose, and wheat flour, bringing sugar totals to 12 to 20+ grams per half-cup. A typical two-cup bowl of tomato soup can have upwards of 80 grams of sugar. I had lunch with my non-diabetic friend who had a one-hour postprandial blood sugar of 157 mg/dl after tomato soup.
Sure, granola contains a lot of fiber. But most granolas come packed with sugars in various forms. One cup of Kellogg's Low-fat Granola with Raisins contains an incredible 72 grams (net) carbohydrates, of which 25 grams are sugar. I've seen people eat granola straight out of the box as a snack and consume a couple of cups. That would be 144 grams of carbohydrates The same holds true for granola bars.
Sauces, especially those used in restaurants, are typically thickened with cornstarch. Cornstarch behaves much like sugar: nearly pure carbohydrate with little else, providing 120 grams carbohydrates per cup. The glycemic index (blood sugar-raising properties) of cornstarch are identical to that of sucrose. I recently had brunch at an Indian restaurant. While most of the dishes were vegetables, some goat and chicken, all were in various spicy sauces. My blood sugar broke past 130 mg/dl one hour afterwards. There must have been plenty of cornstarch in the sauces.
Given modern appetites and serving sizes, you can see that it is very easy to get carried away and, before you know it, get exposed to extraordinary amounts of sugar and carbohydrates eating foods you thought were healthy.
And don't be fooled by claims of "natural" sugar. Sugar is sugar - Just check your blood sugar and you'll see. Raw cane sugar, beet sugar, and brown sugar have the same impact as white table sugar. Honey, maple syrup, and agave? They're worse (due to fructose).