If you’re watching your calories, it’s best to limit your intake of fried vegetables, since they tend to absorb so much oil. That’s because of their high water content, which the frying fat largely replaces. How much fat is absorbed depends on the type of vegetable, type of oil, frying time and temperature and other factors.
In a Greek study several years ago, vegetables were pan-fried in olive oil at 340°F or less. The amount of oil absorbed ranged from 6 grams for 3½ ounces of green peppers and zucchini to 42 grams (more than 3 tablespoons) for eggplant, while calories increased 3 to 18 times. For example, frying green peppers increased calories from 23 to 74, while potatoes went from 65 to 240 calories, and eggplant from 25 to a whopping 446.
Eggplant is a notorious fat absorber because of its spongy texture. In the study, coating it with flour or batter before frying reduced oil absorption and thus calories (to as low as 193), compared to plain pan-frying. But the coating increased oil and calories in zucchini.
If you do fry veggies, the trick is to get the oil hot enough first so that it quickly creates a thin crust that seals in moisture but limits oil absorption. Because the crust forms a barrier, the food essentially steams itself inside.
To find the “right” temperature, heat the oil in a pan, then add a small piece of the vegetable and wait until it sizzles before adding the rest. For deep-frying, use a frying, candy or infrared thermometer (the temperature should reach somewhere between 325° and 375°F, depending on the food and recipe instructions). Frying at the right temperature also makes for the best texture and flavor. To keep calories down, use just enough oil to coat the vegetables and then drain the fried veggies on a paper towel to remove excess oil.
And choose a healthful oil, such as canola, corn, olive, peanut, safflower or sunflower, rather than frying in animal fat. As seen in a 2012 study from Spain, fried foods are not associated with increased heart disease or mortality when such oils are used.