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Nutrition

Human Performance & Health › Nutrition

This page covers what published research and public health agencies say about the main parts of a diet: energy balance, the three macronutrients, common micronutrient shortfalls, fiber, water, meal timing, processed food and detox products. Each claim names its source; where trials disagree, both are given.

Energy balance

A 2012 consensus statement in the American Journal of Clinical Nutrition opens with the principle that “body weight change is associated with an imbalance between the energy content of food eaten and energy expended by the body to maintain life and to perform physical work,” and adds that “we need a better understanding of the components of energy balance and their interactions over various time scales” (Hall et al., 2012, abstract as reproduced by IAFNS). The same intake does not produce the same result in everyone: when 12 pairs of identical twins were overfed by 1,000 kcal a day, 6 days a week, for 84 days, “The mean weight gain was 8.1 kg, but the range was 4.3 to 13.3 kg,” while “The similarity within each pair in the response to overfeeding was significant” (Bouchard et al., 1990).

Protein

MedlinePlus: “Proteins are the building blocks of life”; “You need protein in your diet to help your body repair cells and make new ones”; “The basic structure of protein is a chain of amino acids”; and “Essential amino acids cannot be made by the body” (MedlinePlus, Protein in diet, reviewed April 1, 2025).

For people who train, the International Society of Sports Nutrition concluded that a total daily protein intake of about 1.4 to 2.0 grams per kilogram of body weight is sufficient for most exercising individuals to build and maintain muscle (Jäger et al., 2017). A meta-analysis of resistance-training studies found that “Protein supplementation beyond total protein intakes of 1.62 g/kg/day resulted in no further RET-induced gains in FFM” (fat-free mass), and that supplementation “significantly enhanced changes in muscle strength and size during prolonged RET in healthy adults” (Morton et al., 2018). The Dietary Guidelines for Americans, 2025 to 2030 give 1.2 to 1.6 grams per kilogram per day for the general population. These are figures from the research and the guidelines, given as information, not as a prescription; a clinician or registered dietitian can say what applies to a given person.

Carbohydrate and fat

Carbohydrate. Muscle stores carbohydrate as glycogen, which is rebuilt after exercise; in the first hours carbohydrate at about 1 gram per kilogram of body mass is described as “optimizing this process” (Burke, van Loon & Hawley, 2017).

Fat. Nutrition.gov describes an NIH article on “how fat provides energy, and helps our guts absorb certain vitamins from food” (Nutrition.gov, Fats). The NIH Office of Dietary Supplements: “ALA and linoleic acid are considered essential fatty acids, meaning that they must be obtained from the diet” (ODS, Omega-3 Fatty Acids).

Low-fat versus low-carbohydrate. In a 12-month randomized trial (DIETFITS), weight change was “−5.3 kg for the HLF diet vs −6.0 kg for the HLC diet” (healthy low-fat versus healthy low-carbohydrate; mean difference 0.7 kg, 95% confidence interval −0.2 to 1.6 kg), and the authors reported “no significant difference in weight change” between them (Gardner et al., 2018).

Micronutrient shortfalls

The scientific report of the 2020 Dietary Guidelines Advisory Committee found that, for Americans ages 1 year and older, “current underconsumption of vitamin D, calcium, dietary fiber, and potassium is of public health concern” (2020 DGAC report, Part A).

The NIH Office of Dietary Supplements (ODS) fact sheets add:

  • Magnesium: “Many people in the United States consume less than the recommended amounts of magnesium” (ODS, Magnesium, updated January 6, 2026).
  • Potassium: “Dietary surveys consistently show that people in the United States consume less potassium than recommended” (ODS, Potassium, updated June 2, 2022).
  • Vitamin D: “Vitamin D promotes calcium absorption in the gut”; the groups ODS names as at risk of inadequacy are breastfed infants, older adults, people with limited sun exposure, people with dark skin, people with conditions that limit fat absorption, and people with obesity or who have had gastric bypass surgery (ODS, Vitamin D).
  • Vitamin B12: for vegetarians and vegans, “vitamin B12 supplements can substantially reduce the risk of deficiency,” and regular users of metformin or acid-reducing drugs “should discuss their vitamin B12 status with their health care providers” (ODS, Vitamin B12).

Whether any of these applies to a given person is a question for a clinician, who can order the blood tests the ODS fact sheets describe. Individual nutrients are covered on Foundational Supplements.

Fiber

A series of systematic reviews and meta-analyses in The Lancet reported that “Observational data suggest a 15-30% decrease in all-cause and cardiovascular related mortality” with higher fiber intake, that risk reduction “was greatest when daily intake of dietary fibre was between 25-29 grams,” and that the dose-response evidence indicates “the relationships may be causal” (Reynolds et al., 2019). A 2017 review states that “national consumption surveys indicate that only about 5% of the population meets recommendations” (Quagliani & Felt-Gunderson, 2017).

Water

The National Academies’ 2004 report found that women “who appear to be adequately hydrated consume an average of approximately 2.7 liters (91 ounces) of total water” a day and men “average approximately 3.7 liters”; “About 80 percent of people’s total water comes from drinking water and beverages,” and “the other 20 percent is derived from food.” The panel added that “The vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide,” and that “caffeinated beverages can contribute as much as noncaffeinated options” toward daily needs (National Academies, February 11, 2004).

Drinking far past that during hours of heavy sweating carries a named hazard: NIOSH warns that drinking too much “can cause a medical emergency because the concentration of salt in the blood becomes too low” (NIOSH 2017-126); the figures are on Nutrition, Hydration & Recovery Support.

Meal timing: still studied

In a 12-month randomized trial of 139 patients with obesity, all on daily calorie restriction, adding an 8-hour eating window “did not produce greater weight loss,” and the authors found no significant difference between the groups (Liu et al., 2022, as described by Most, 2024). A 2024 re-analysis in Frontiers in Nutrition argues that the result “is not consistent with a clinical conclusion that time-restricted eating was not beneficial”: mean weight loss was 8.0 kg with the eating window and 6.3 kg without, and the confidence interval for the difference (−4.0 to 0.4 kg) includes differences that would matter clinically (Most, 2024). Both arms restricted calories, so the trial tests the window on top of calorie restriction, not on its own.

Processed food

In an NIH inpatient trial, 20 adults spent two weeks on an ultra-processed diet and two weeks on an unprocessed diet, in random order, with meals offering the same calories, sugars, fiber, fat and carbohydrates and permission to eat as much as they wanted. On the ultra-processed diet they ate “about 500 calories more per day,” gained about 0.9 kg (2 pounds), and lost a similar amount on the unprocessed diet (NIH news release, May 16, 2019; Hall et al., Cell Metabolism, 2019). It was a single one-month study in 20 people.

Detox products

The National Center for Complementary and Integrative Health reports that a 2015 review found “no compelling research to support the use of ‘detox’ diets for weight management or eliminating toxins from the body,” that “There have been no studies on long-term effects of ‘detoxification’ programs,” and that some programs “can be unsafe and falsely advertised”; it lists colon cleansing side effects, illness from unpasteurized juices, kidney-stone risk from high-oxalate juices, and electrolyte imbalances from prolonged fasting on water and herbal tea (NCCIH, Detoxes and Cleanses, March 2025).

How nutrition connects to the rest of the system

The Biological Foundation covers the cellular side; Fitness & Movement covers training; Sleep & Recovery covers sleep; Energy & Fatigue covers causes of fatigue; Foundational Supplements and Supplements cover what the NIH and FDA say about supplements. All of it hangs off the pillar hub at Human Performance & Health.

What comes next

Fitness & Movement is the next lever page. Deeper guides on protein, micronutrients, fiber, hydration and meal timing open beneath this page over time.

GoldBlock Workshop is educational. We explain how the body works and what the research shows. We do not diagnose, treat, cure, or prevent any disease, and nothing here is personal medical advice. Talk to a qualified professional about your own situation, especially before making changes if you are pregnant, managing a health condition, or taking medication.

Sources and further reading

We build on the work below, and we credit it by pointing to the published research and to the National Institutes of Health rather than reproducing it.

  • Energy balance. Hall, Heymsfield, Kemnitz, Klein, Schoeller & Speakman, “Energy balance and its components: implications for body weight regulation,” American Journal of Clinical Nutrition 95(4):989-994 (2012). Abstract read 2026-10-19 on the IAFNS publication listing. IAFNS · Bouchard et al., “The response to long-term overfeeding in identical twins,” New England Journal of Medicine 322(21):1477-1482 (1990). Abstract read 2026-10-19 (QxMD copy of the PubMed record). PubMed
  • Protein basics. MedlinePlus Medical Encyclopedia, “Protein in diet,” review date April 1, 2025 (read 2026-10-19). MedlinePlus
  • Protein intake ranges. Jäger et al., “International Society of Sports Nutrition Position Stand: Protein and Exercise,” Journal of the International Society of Sports Nutrition (2017). PubMed
  • Protein and muscle, the plateau. Morton et al., British Journal of Sports Medicine 52:376-384 (2018). Abstract read 2026-10-19 (Auckland University of Technology repository). AUT repository
  • Protein, general population. Dietary Guidelines for Americans, 2025 to 2030 (January 2026): 1.2 to 1.6 g/kg/day (read 2026-10-19 in pass 1 of this audit through the NMSU copy, and in the Oklahoma State University Extension summary FCS-3629, June 2026). PDF
  • Glycogen. Burke, van Loon & Hawley, “Postexercise muscle glycogen resynthesis in humans,” Journal of Applied Physiology (2017). PubMed
  • Fat. Nutrition.gov, “Fats” (USDA National Agricultural Library; no date shown; read 2026-10-19). Nutrition.gov · NIH ODS, “Omega-3 Fatty Acids” (read 2026-10-19). NIH ODS
  • Low-fat versus low-carbohydrate. Gardner et al., “Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults” (DIETFITS), JAMA 319(7):667-679 (2018). Read 2026-10-19 from a copy hosted at gwern.net. Copy
  • Nutrients of public health concern. Scientific Report of the 2020 Dietary Guidelines Advisory Committee, Part A, Executive Summary (read 2026-10-19). PDF
  • Magnesium, potassium, vitamin D, vitamin B12. NIH Office of Dietary Supplements Health Professional fact sheets (read 2026-10-19; B12 quotations verified 2026-10-18): Magnesium · Potassium · Vitamin D · Vitamin B12
  • Fiber intake and outcomes. Reynolds et al., “Carbohydrate quality and human health: a series of systematic reviews and meta-analyses,” The Lancet 393(10170):434-445 (2019). Read 2026-10-19 (University of Dundee accepted manuscript). Dundee
  • The fiber gap. Quagliani & Felt-Gunderson, “Closing America’s Fiber Intake Gap,” American Journal of Lifestyle Medicine (2017). Abstract read 2026-10-19 (MetaTOC listing). Journal
  • Water. National Academies, “Report Sets Dietary Intake Levels for Water, Salt, and Potassium,” February 11, 2004 (read 2026-10-19). National Academies
  • Overdrinking and low blood salt. NIOSH, “Heat Stress: Hydration,” DHHS (NIOSH) Publication No. 2017-126 (read 2026-10-18). stacks.cdc.gov
  • Meal timing. Liu et al., “Calorie Restriction with or without Time-Restricted Eating in Weight Loss,” New England Journal of Medicine (2022), as described in Most DE, “Evaluating evidence regarding the efficacy of time-restricted eating for weight loss,” Frontiers in Nutrition 11:1428998 (2024), read 2026-10-19. PubMed · Frontiers
  • Processed food. NIH news release, “NIH study finds heavily processed foods cause overeating and weight gain,” May 16, 2019 (read 2026-10-19), on Hall et al., Cell Metabolism (2019). nih.gov
  • Detox products. NCCIH, “Detoxes and Cleanses: What You Need To Know,” March 2025 (read 2026-10-19). NCCIH