In a report that appears certain to dismay some powerful sectors of the food industry and fuel a controversy over the link between diet and disease, a quasi-governmental panel yesterday advised Americans to change their eating habits if they want to avoid cancer.

Urging drastic changes in the national diet, a special committee of the National Academy of Sciences and National Research Council called for a sharp cutback in the consumption of fatty meat, butter, whole milk, alcohol and salt- or smoke-cured meats such as ham, sausage and bacon, and an increase in the consumption of fruits, vegetables and whole-grain bread or cereals.

Only two years ago the Food and Nutrition Board of the same bodies said no one knew enough to make such sweeping dietary recommendations for everyone. And the U.S. Department of Agriculture, under the Reagan administration, has been soft-pedaling some largely similar dietary guidelines issued by the USDA and the Health, Education and Welfare Department in 1980, during the Carter administration.

At his confirmation hearing, Agriculture Secretary John R. Block said, "I'm not so sure government should get into telling people what they should or shouldn't eat"--apparently a reference to the dietary guidelines, which had been criticized by some in the food industry for their warnings on cholesterol, fats, sugar and salt.

Those guidelines were concerned with preventing heart disease, not cancer. But the government's National Cancer Institute tentatively advised a low-fat, high-fiber cancer prevention diet in 1979 and asked the National Research Council to make a more definite recommendation.

The meat industry immediately criticized yesterday's advice, saying it was "misleading" and "does no service to the public." Studies fail to show that a reduction in protein and fat consumption will reduce cancer incidence, said Dr. George Wilson, American Meat Institute vice president for scientific affairs.

The committee found no evidence that individual chemical additives or contaminants--such as preservatives, dyes, molds, bacteria, pesticide residues--are major cancer risks.

The group also said that the protective elements in fruits and vegetables--largely vitamin C and carotenes (which the body converts to vitamin A)--should come from fruits and vegetables, rather than from high-dose nutrient supplements.

Dr. Clifford Grobstein, University of California biologist and committee chairman, said yesterday that "the evidence is increasingly impressive that what we eat does affect our chances of getting cancer. By controlling what we eat we may prevent diet-sensitive cancers," especially breast, colon or large bowel, stomach, prostate, bladder, skin, lung and esophagus cancers.

"Our committee's recommendations should not be regarded as assuring a cancer-free life," Grobstein emphasized, but he said the committee's advice is the best possible to avoid not only cancer but also heart disease, because a diet high in fats, particularly animal fats, seems linked to both disorders.

Grobstein said it is not possible yet to say how much any one cancer may be reduced in incidence by a change in diet. But animal studies and observation of many human populations led the committee to tell Americans to:

* Restrict to 30 percent the daily calorie intake from foods high in fats, such as fatty cuts of meat, whole milk dairy products, cooking oils and fats. The average American now gets 40 percent of daily calorie intake from fats.

* Eat whole-grain (like whole wheat) cereal products and fruits and vegetables daily, particularly foods like oranges, grapefruit, dark green leafy vegetables, carrots, winter squash, tomatoes, cabbage, broccoli, cauliflower and brussel sprouts.

* Eat "very little" salt-cured, pickled or smoked foods, such as hot dogs, bologna and other sausages, ham, bacon and smoked fish.

* Drink alcohol "only in moderation," especially if you smoke. Grobstein declined to define "moderation." Dr. Arthur Upton, former National Cancer Institute director, once defined "too much" alcohol as any more than two drinks a day.