When Joe Bernstein meets friends for a dinner out, he knows ahead of time that there will be nothing on the menu for him to eat.

"They do accommodate me, though," he said. "I just ask for a dish of sliced avocado."

You could say that Bernstein is mad about fruit. He is a fruitarian, or frugivore, and he adheres to a lifestyle that is a niche within a subset of vegetarianism.

Bernstein, who lives in New York City, eats only raw fruit, a diet that includes some nuts and non-sweet fruit like avocado and tomato. A typical day of meals may include sunflower seeds with a few servings of fruit, such as pears or plums, for breakfast; a coconut shake with bananas for lunch; and Brazil nuts with tomatoes and avocado for dinner.

For the typical, omnivorous American, it's hard to believe that he isn't starving. Yet Bernstein, who is a healthy 145 pounds and 5 feet 10, insists that his all-fruit diet is completely satisfying.

The reasons people turn to fruitarianism vary. For some, like Bernstein, the motivation centers on conservation. Fruits fall from trees or vines naturally, and it isn't necessary to kill the plant or take away from the earth to make a meal.

Robert Dyckman, who founded Acting Consciously, feels that his food choices yield a change beyond physical appearance.

"Emotionally, I'm calm and poised," said Dyckman, who blogs about his diet at actingconsciously.blogspot.com. "I can empathize with others much easier."

Dyckman volunteers as a leader at the Raw Health and Happiness Society, which meets weekly and serves as a "safe and supportive environment for self-growth," he said. Dyckman, who said that he hasn't been sick in seven years, said that his diet did not alienate him from his non-fruitarian friends.

"I love parties," Dyckman said. "And I love to get together with my friends, and that doesn't necessarily require eating . . . and if there's food involved, I have the opportunity to share gorgeous organic produce with my friends."

Cynthia Sass, a registered dietitian and spokeswoman for the American Dietetic Association, has had a number of clients ask her about the fruitarian diet. While Sass is a vegan, she has concerns about a strict fruitarian diet and recommends a Vitamin B12 supplement. The amount of nuts that a fruitarian would have to ingest to fulfill a protein requirement would exceed the fat allotment for the day, according to Sass.

Some dietitians have expressed concern with the potential for fruitarians to become sugar addicts, but Aimee Cavenecia, an aspiring fruitarian in New York, isn't worried.

"People can be addicted to love, to meat, to exercise," Cavenecia said. "I would rather be addicted to something cleansing than something toxic."