Phyllis McClain, 75, (left) and Alice Barnes, 76, makes choices at the salad bar at Hattie Holmes Senior Wellness Center in Washington, DC (Photo by Bonnie Jo Mount/The Washington Post)

America, please eat more fruits and vegetables.

A new report by the Dietary Guidelines Advisory Committee, which convenes every five years, says that the rest of the American diet is having devastating effects: about two-thirds of American adults are overweight or obese. And maybe worse, about half of American adults - about 117 million people - have preventable chronic diseases related to poor diet and physical inactivity, the group said.

This dismal diagnosis is the foundation for the group’s report, which provides the scientific basis for the nation’s Dietary Guidelines, the advice booklet that will be issued by the federal government late this year.

“I wouldn’t call it gloomy,” said Marian Neuhouser, a committee member from Fred Hutchinson Cancer Research Center in Seattle, WA. “I call it reality.”

The committee's report amounts to a scientific update regarding what is known about healthy eating.

For the first time, the committee is recommending that the government should consider the environment when telling Americans what they should eat, a move that could have a significant impact on the amount of meat people eat.

It also, for the first time, addressed concerns about coffee, saying that there is strong evidence that moderate consumption is not associated with long-term health risks.

The panel also reversed decades of warnings about dietary cholesterol, as The Post previously reported. For years, the Dietary Guidelines have advised Americans to consume no more than 300 milligrams of cholesterol a day, a warning that limited egg consumption for many Americans. The limit arose from the belief that eating cholesterol would lead to high levels of "bad" cholesterol in the blood. But, the group concluded, no such warning is necessary.

[U.S. government: Cholesterol isn't as bad as we thought]

"Available evidence shows no appreciable relationship between consumption of dietary cholesterol and [blood] cholesterol," the report found.

The bulk of the report issued today, which runs to 571 pages, outlines reams of scientific evidence about what's good to eat. And in terms of dietary advice, it can be summarized as follows:

- A healthy diet is rich in vegetables, fruits, whole grains, low- or non-fat dairy, seafood, legumes, and nuts.

- It is moderate in alcohol

- And it is lower in red and processed meat, and low in sugar-sweetened foods and drinks and refined grains.

The government has published  dietary guidelines since 1977, and during that time, those guidelines did not avert what many nutritionists consider a dietary disaster -- the nation slipped into an obesity epidemic.

"In the past, we haven't been able to change the way people are eating very much," said Alice Lichtenstein, a committee member and nutrition professor at Tufts University. "One of the major focuses of this report is, rather than nutrients, the whole diet."

[So can I binge on eggs now? Here's what you need to know.]

So in compiling the evidence on diet and health, the group took a different tack from previous committees. Rather than focusing on the health effects of individual nutrients, it focused on how entire diets affect health.

The committee reviewed studies that looked for associations between diets and major diseases such as cancer, heart troubles and diabetes.

With regard to what people ought to eat, their research turned up the most consistent evidence for the health benefits of fruits and vegetables. The evidence for the benefits of whole grains was only slightly less consistent.

And with regard to potentially dangerous items, the group found  "moderate to strong evidence" that higher consumption of red and processed meats, refined grains and sugar-sweetened foods and beverages are detrimental.

Read more:

How cholesterol went from 'public menace' to 'not a nutrient of concern'

How many eggs a day is okay? Your questions, answered. 

 Top nutritional panel: Stop eating so much meat -- to protect the environment

Upcoming event March 26: Changing the Menu