Diet

A diet, in nutrition, is the habitual pattern of foods and beverages a person or population consumes over time. Nutrition scientists evaluate diets not meal by meal but as patterns, asking whether intake meets energy and nutrient needs and whether it raises or lowers the risk of disease. The World Health Organization (WHO) identifies unhealthy diets as a major risk factor for disease and disability, and healthy diets as protective against malnutrition in all its forms as well as noncommunicable diseases including diabetes, heart disease, stroke, and cancer¹.

What makes a diet healthy

The exact composition of a healthy diet varies with age, sex, activity level, cultural context, locally available foods, and dietary customs, but WHO holds that the underlying principles stay the same¹. Adequacy means meeting, without exceeding, macronutrient and micronutrient needs so that deficiencies are prevented. Balance means total energy intake matches energy expenditure, with a suitable distribution across protein, fats, and carbohydrates. Moderation limits intake of components that may harm health, and diversity means a wide variety of nutritious foods within and across food groups¹. A diet must also be safe, meaning free of microbial and chemical contaminants¹.

The foundation, in WHO's formulation, is a variety of minimally processed and unprocessed foods low in unhealthy fats, free sugars, and sodium¹. Free sugars are monosaccharides and disaccharides added to foods by manufacturers, cooks, or consumers, plus sugars naturally present in honey, syrups, and fruit juices; WHO advises reducing them without substituting non-sugar sweeteners such as aspartame, sucralose, or stevia¹.

Quantitative guidance from WHO

WHO expresses its advice as intake ranges tied to total energy. Carbohydrates should come primarily from whole grains, vegetables, fruits, and pulses, and for most people should represent roughly 45 to 75% of daily energy¹. Fat is essential; two fatty acids, linoleic acid and α-linolenic acid, can only be obtained from food, and adults should get a minimum of 15% of daily energy from fat, with total fat limited to 30% or less to help prevent unhealthy weight gain¹. Unsaturated fat from fish, avocado, nuts, and plant oils is preferable to saturated fat and to trans fat of any kind, and industrially produced trans fats should be avoided outright¹.

Protein at 10 to 15% of daily energy is generally sufficient for adults, about 50 to 75 g for a person of healthy body weight eating about 2000 calories per day; higher intakes may be warranted in adolescence and for people building significant muscle mass, while excessive intake can place a metabolic burden on the kidneys¹. High sodium intake raises blood pressure, a pathway to cardiovascular disease, while potassium mitigates sodium's effects; WHO therefore pairs the 5 g salt ceiling with the suggestion that at least 3510 mg/day of potassium for adults may be beneficial¹.

For infants, WHO advises exclusive breastfeeding for the first six months, continued breastfeeding to two years and beyond, and complementary foods from six months with no added salt or sugar¹.

Dietary guidance in the United States

Federal dietary advice in the United States has evolved through a series of food guides. In 1943, during World War II, the USDA issued the "Basic Seven" guide, which accounted for wartime ration shortages but gave no portion sizes; in 1956 it was simplified to the Basic Four, with rough daily serving suggestions⁴. In 1977 a Senate committee led by Senator George McGovern released Dietary Goals for the United States, recommending less sugar, sodium, and fat and more complex carbohydrates; the goals drew backlash from industry and parts of the science community over the strength of the evidence^{4 • 5}.

That dispute produced the modern arrangement: the first Dietary Guidelines for Americans appeared in 1980, issued jointly by the Departments of Agriculture and Health and Human Services, and the two departments have updated and released the document together every five years since^{2 • 6}. Each edition is built on a scientific report from a Dietary Guidelines Advisory Committee, a practice first used for the 1985 edition⁵. Visual icons have changed alongside the text: the Food Guide Pyramid served from 1992 to 2005, MyPyramid from 2005 to 2011, and MyPlate from 2011 to 2026².

The 2025-2030 edition

On January 7, 2026, Health Secretary Robert F. Kennedy Jr. and Agriculture Secretary Brooke Rollins released the Dietary Guidelines for Americans, 2025-2030, the 10th edition, with a new visual icon: an inverted food pyramid placing protein, dairy, healthy fats, vegetables, and fruits at the top and whole grains at the base^{3 • 7}. The edition's stated emphasis is eating "real food": whole or minimally processed foods, with official guidance for the first time calling on Americans to avoid highly processed food⁸. It sets a protein target of 1.2 to 1.6 grams per kilogram of body weight per day, three servings of vegetables and two of fruit daily, and 2 to 4 servings of whole grains⁸.

The protein recommendation drew expert criticism. The guidelines tell Americans to "prioritize protein foods at every meal" and advise increasing daily intake, up to double previous recommendations, emphasizing red meat, whole milk, and other animal sources; nutrition experts responded that Americans already consume more protein than needed and that sharply higher intake could increase body fat and diabetes risk⁹. The edition also encourages full-fat dairy and cooking with butter and beef tallow, foods high in saturated fat, while retaining the longstanding 10%-of-calories saturated fat ceiling; Marion Nestle, professor emerita of nutrition, food studies, and public health at New York University, called that combination contradictory, since a diet rich in meat and full-fat dairy makes the 10% limit hard to meet³. The American Heart Association, which recommends a 6% saturated fat limit, urged consumers to prioritize plant proteins, seafood, and lean meats³.

The edition also dropped specific alcohol limits, which had advised at most two drinks a day for men and one for women, in favor of the statement that people should "consume less alcohol for better overall health," with complete avoidance for pregnant women and people recovering from alcohol use disorder³.

Why dietary guidance matters at population scale

The Dietary Guidelines set standards for government-funded food programs including the National School Lunch Program and the Supplemental Nutrition Assistance Program (SNAP), and provide the foundation for federal nutrition programs and policies^{3 • 7}. The USDA press release accompanying the 2025-2030 edition noted that nearly 90% of US health care spending goes toward treating chronic disease, much of it linked to diet and lifestyle¹⁰. Globally, WHO works through food-environment policies such as nutrition labeling, school food standards, marketing restrictions on foods aimed at children, and fiscal measures like taxes and subsidies, and has produced more than 15 guidelines over the last decade on salt, sugars, fats, trans fat elimination, complementary feeding, and breastfeeding^{1 • 11}.

References

1. Healthy diet, World Health Organization fact sheet (26 January 2026)
2. History of Dietary Guidance Development in the United States, DietaryGuidelines.gov
3. New Dietary Guidelines Urge People to Eat More Protein and Fewer Processed Foods, TIME (January 7, 2026)
4. The Rise, Fall, and Potential Return of the Food Pyramid, TIME
5. The U.S. Food Guidelines Have Always Been Controversial, TIME (2016)
6. Previous Editions, DietaryGuidelines.gov
7. New dietary guidelines urge Americans to avoid processed foods and added sugar, AP News (January 7, 2026)
8. Eat Real Food, realfood.gov (USDA/HHS)
9. New diet guidelines say to double up on protein, but nutrition experts are wary, AP News (January 19, 2026)
10. Kennedy, Rollins Unveil Historic Reset of U.S. Nutrition Policy, USDA Food and Nutrition Administration
11. Healthy diet, WHO health topics

Topic: Encyclopedia › Life and health › Human health and medicine › Nutrition and personal wellbeing › Dietary patterns and wellness practices › Dietary patterns and dieting › Dietary practices, restrictions, and avoidance

Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026

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