Story highlights Check out menus in advance to be sure they offer options

Ask about "off-menu" items, or custom-order your meal

(CNN) Ordering fast food can be tricky for people who are trying to eat healthfully, but it can be particularly challenging for vegetarians. Menus are often limited in vegetarian staples such as beans, lentils, whole grains and vegetables.

The good news is that more and more restaurants are catering to meatless customers, which now number approximately 8 million adults in the United States, with many more trying to eat less meat in general for health reasons.

"I am seeing more options out there for plant-based eaters who want to grab fast food," said Sharon Palmer, a vegetarian, nutritionist and author of "Plant-Powered for Life."

Vegetarian dining requires some careful planning, however. Here are some tips and strategies for eating well at fast food restaurants if you are a vegetarian or vegan:

Check out menus in advance. Since some chains have more vegetarian options than others, you should go online or try calling a restaurant to see whether there's something you will eat. If the menu seems limited, it may be worth traveling a bit farther if it means you'll get healthier, more appealing meatless options.

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