By the third day the visions start.

Not the wispy, first flashes of nirvana promised by friends who fast, but raging Italian spectres. A phantom plate of creamy al dente spaghetti, slathered in sauce, hovers at eye levle. Tagliatelli tangles thoughts; gnoccki haunts dreams.

Herbal teas don't divert the hungering stomach. And friends are uselss: they all go out to eat.

Fasting, voluntary fasting, once the province of the saintly and the religious, now has cachet. From Beverly Hills to Broadway and in areas along the way, people were fasting for a host of reasons. The most common reason is for weight, but people also fast to cleanse their systems of the additives in modern food, for political reasons, or to empathize with the hungry of the world.

Mostly it's philosophy, not fat, that inspires the hard-core fast. And by fast is meant "straight water" - maybe with a little fruit juice mixed in, maybe in an herbal tea, but mainly unadulterated H-2-0. What rewards one gets from this, besides a possible hunger headache, depends on what one looks for.

"It repairs the body," maintains Dick Gregory, actor, comedian, protestor and faster par excellence. In 1967, Gregory fasted for 40 days on water to protest the Vietnam War. He gave 67 speeches during the fast and after the 21st day, said he just "kept getting stronger and stronger."

He also went from 280 poungs t 95.

Aside from a method of protesting, Gregory said that fasting "increases the psychic powers that every one of us has naturally. I fast for 30 days every year and then three or four times a week. My wife, Lillian, and every one of my 10 children fasts - for the youngest ones only one day a week on fruit juice."

Nobody knows how many people fast voluntarily, but it's a prominent fad among actors and luminaries in the media. Singer-actor Pat Boone fasts. So does Valerie "Rhoda" Harper, though her agent doesn't think fasting a fit subject for her to talk about.

Anchorwoman Kelly Lange at Los Angeles' KNBC fasts. She entered the ranks of the spare three years ago.

"I went to my doctor because I was feeling really down," recalls Lange. "You know, the blahs. I didn't have any energy and my doctor suggested that I fast for a week. I thought he was nuts."

The skeptical Lange followed the doctor's orders, however, and "it made me feel good. So now I fast once a week on Mondays so I empty out all the junk I've had over the weekend."

Lange maintains that she doesn't fast to lost weight, but says one of the side-effects is "that you lose weight if you need to. Usually, though, it's just for the energy. I eat nothing solid, just liquids, usually tea or coffee."

Among the ordinary citizenry, similar effects from fasting are lauded. Says one woman who fasted as a "Spring - cleaning for my body" for the first time this year: "At the end of three and a half days. I felt like St. Teresa of Avila. It was wonderful. I felt that with two more days, I could have levitated, I was feeling so high."

All this on a little water and tea. But there's more.

The American Natural Hygiene Society in Chicago has been touting the benefits of fasting recommending its own brand of distilled water - since 1949. Among their publications are "Fasting Can Save Your Life" and "Triumph Over Disease by Fasting and Natural Diet," the latter promising to show how "the oldest natural remedy, fasting, can rescue you from debilitating disease and possible death."

Outside this kind of hyberhole and hoopla, however, the mainstream of medical science remains skeptical.

"Total fasting is nonsense," says Washington internist, Dr. Gil Eisner. "Jews two observe Yom Kippur strictly - they've all got a headache by the end of the day.

West about that sense of euphoria fasting in supposed to induce, the visions that the saints had that are now explained as a side-effect of fasting."

Dr. James Ramey, another local internist says it's all clubhouse. "First you'se going to feel midly nauseated, then mildly depressed. There is no evidence that you lose any bad humors through fasting. I doubt there's any euphoria attached to it either. Some of the euphoria is probably that delicious feeling of losing weight. In the long run that's going to fail too. It's all fluid, not fat (that one loses)."

Still, there are testimonials to the efficacy of no food. Says one Washington man who fasted on water for two weeks, "I lost 20 pounds and I've kept it off. I did it all on water, vitamins and an occasional bouillion cuba in hot water. I wasn't miserable, but I wasn't feeling great either.I spent a lot of time reading cookbooks and planning what I'd eat when I stopped fasting. I found when I quit that I could eat smaller portions and it gave me new insights into how much fool we waste."

The sense of how much food the Western world uses and how little is available in other places that experience starvation and famine drew Sen. Mark Hatifield (R-Ore.) in fasting.

"My interest was trigged when I first got involved in the hunger problems in the world," said the Oregon Republican. "I felt that one could really sense the problem only if one had experienced the pangs of hunger, so I fasted as part of that involvement. It's affected my whole dietary practice."

Dietary practices aside, on the fourth day of one woman's first fast life had lost some of its joy. With day five, she had a slightly slimmer, questionably healthier body and a great and glorious appetite.

Perhaps for epiphanies from the beyond. But certainly not for solid food.