Rejecting the advice of its scientific advisers, the federal government has released new dietary recommendations that sound a familiar nutritional refrain, advising Americans to “make every bite count” while dismissing expert recommendations to sharply reduce consumption of sugar and alcoholic beverages.

The “Dietary Guidelines for Americans” are updated every five years, and the latest iteration arrived on Tuesday, 10 months into a pandemic that has posed a historic health threat to Americans. Confined to their homes, even those who have dodged the coronavirus itself are drinking more and gaining weight, a phenomenon often called “quarantine 15.”

The dietary guidelines have an impact on Americans’ eating habits, influencing food stamp policies and school lunch menus and indirectly affecting how food manufacturers formulate their products.

But the latest guidelines do not address the current pandemic nor, critics said, new scientific consensus about the need to adopt dietary patterns that reduce food insecurity and chronic diseases. Climate change does not figure in the advice, which does not address sustainability or greenhouse gas emissions, both intimately tied to modern food production.

A report issued by a scientific advisory committee last summer recommended that the guidelines encourage Americans to make drastic cuts in their consumption of sugars added to drinks and foods to 6 percent of daily calories, from the currently recommended 10 percent.

High rates of overweight and obesity in the United States are linked to serious chronic health conditions like heart disease and Type 2 diabetes, the panel noted; the conditions also increase the risk of developing severe Covid-19 illness.

The committee also called for limiting daily alcohol consumption to one drink a day for men, stating clearly that consuming higher amounts of alcohol is associated, on average, with an increased risk of death, compared with drinking lower amounts. But the current recommendation remains one drink per day for women, and two for men.

Officials at the Department of Agriculture and the Department of Health and Human Services rejected both the sugar and the alcohol caps.

Perhaps confusingly, the guidelines say “the preponderance of evidence supports limiting intakes of added sugars and alcoholic beverages to promote health and prevent disease; however, the evidence reviewed since the 2015-2020 edition does not substantiate quantitative changes at this time.”

The new guidelines do say for the first time that children under 2 should avoid consuming any added sugars, which are found in many cereals and beverages.

The main sources of added sugars in the American diet are sweetened beverages — including sodas, as well as sweetened coffees and teas — desserts, snacks, candy, and breakfast cereals and bars. Most Americans exceed even the 10 percent benchmark; sugars make up 13 percent of daily calories, on average.

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Critics were disappointed that the federal agencies had ignored the recommendations of the scientific advisory committee. “I’m stunned by the whole thing,” said Marion Nestle, a professor emerita of nutrition and food studies at New York University and author of several books on the government’s dietary guidelines.

“Despite repeated claims that the guidelines are science-based, the Trump agencies ignored the recommendation of the scientific committee they had appointed, and instead reverted to the recommendation of the previous guidelines,” she said.

The composition of the dietary advisory committees drew controversy earlier this year, because many of the experts had ties to the beef and dairy industries. Yet the scientists went further in their advice than had previous committees, particularly with the recommendations to limit sugar and alcohol, Dr. Nestle said.

“Those were big changes, and they got all the attention when the report came out last summer for very good reasons — and they were ignored in the final report,” Dr. Nestle said.

“The report was introduced as science-based — they used the word science many times, and made a big point about it,” she added. “But they ignored the scientific committee which they appointed, which I thought was astounding.”

In other ways, the new guidelines are consistent with previously issued federal recommendations. Americans are encouraged to eat more healthy foods, like vegetables, fruits, legumes, whole grains, nuts, seafood, low-fat or nonfat dairy, and lean meat and poultry.

The guidelines urge the nation to consume less sugar, saturated fat, sodium and alcohol, and to limit calorie intake.

For the first time, the guidelines take a “full life-span approach,” trying to sketch out broad advice for pregnant and breastfeeding adults and for children under 2.

One of the recommendations for pregnant women, those about to become pregnant and those who are breastfeeding is to eat ample seafood and fish that is rich in omega-3 fatty acids but low in methylmercury content, which can have harmful effects on a developing fetus. This dietary pattern has been linked to healthier pregnancies and better cognitive development in children.

The new guidelines emphasize the health benefits of breastfeeding, which has been linked to lower risks of obesity, Type 1 diabetes and asthma in children. Foods that are potential allergens, like eggs and peanuts, should be introduced during the first year of life — after four months of age — to reduce the risk of developing allergies.