The Eating-Less Nutrition Gap: what the published data says
Version 1.1, October 11, 2026. Compiled by Zornava from published sources only. It contains no Zornava data. General information, not medical advice.
In one paragraph: about one in eight US adults has used a GLP-1 medication. People taking them eat 16% to 39% fewer calories. Most adults were already short on several nutrients before eating less: 70% below the requirement for vitamin D, 45% for magnesium, 38% for calcium, and more than 90% below the fiber recommendation. Eating less widens gaps that were already there. Every figure below is from a named, published source.
1. How many people are eating less
| Figure | Detail | Source |
|---|---|---|
| 11.8% | of US adults have used a GLP-1 medication (survey of 8,793 adults, April–May 2025) | RAND1 |
| 14% | more say they are interested in using one | RAND1 |
| About 1 in 5 | women aged 50 to 64 have used one, the highest of any group | RAND1 |
PwC's 2026 surveys (secondary). PwC's own pages could not be opened to check these, so each figure below is marked with where it was actually read.
| Figure | Detail | Read from |
|---|---|---|
| 21% | of US households include a current GLP-1 user, up from 9% in January 2025 (PwC US survey of more than 3,000 current, lapsed and considering users, published June 22, 2026) | Search-result excerpt of PwC's page12 |
| 54% | of US users surveyed have been on a GLP-1 for more than a year, up from 38% in 2024 | Search-result excerpt of PwC's page12 |
| 80% / 74% | of current / lapsed US users say they are piecing together their own routines with supporting products | Search-result excerpt of PwC's page12 |
| 40% | of UK users were spending more on vitamins and supplements; 54% were buying more high-protein foods (PwC UK survey of more than 2,300 users, June 2026) | Press coverage13 |
GLP-1 medications are one cause of a smaller appetite among many. Age, illness, recovery and stress produce the same nutritional arithmetic.
2. How much less they eat
| Figure | Detail | Source |
|---|---|---|
| 16%–39% | reduction in calorie intake observed in people taking GLP-1 medications | Joint advisory2 |
| 1,200 / 1,800 kcal | daily intake (women / men) below which vitamin and mineral shortfalls become especially likely | Joint advisory2 |
| 11 nutrients | named as "of concern": iron, calcium, magnesium, zinc, and vitamins A, D, E, K, B1, B12 and C | Joint advisory2 |
3. The starting point: most adults were already short
Share of the US population with usual intake below the Estimated Average Requirement, counting food and supplements together (NHANES 2003–2006, ages 2 and up):3
| Nutrient | Below requirement |
|---|---|
| Vitamin D | 70% |
| Vitamin E | 60% |
| Magnesium | 45% |
| Calcium | 38% |
| Vitamin A | 34% |
| Vitamin C | 25% |
| Vitamin B6, folate, zinc | 8% each |
| Thiamin, vitamin B12, iron | under 6% |
| Figure | Detail | Source |
|---|---|---|
| 3% | of the population had potassium intake above the Adequate Intake | Fulgoni et al.3 |
| 95% / 84% / 46% / 45% | of US adults below the requirement for vitamins D, E, C and A in a later analysis (NHANES 2005–2016, 26,282 adults) | Reider et al.4 |
| More than 90% of women, 97% of men | do not meet the recommended intake for dietary fiber | Dietary Guidelines5 |
| 14 g per 1,000 kcal | the fiber recommendation; the Daily Value is 28 g | Dietary Guidelines,5 FDA6 |
| About 3,400 mg | average daily sodium intake, against a limit of 2,300 mg. Sodium is the exception: most people get too much | Dietary Guidelines5 |
The two NHANES analyses differ because they cover different years and ages and treat supplements differently. Both show the same order: vitamin D and E furthest short, then magnesium, calcium, A and C.
4. The arithmetic of eating less
This table is an illustration, not a measurement. It shows what happens to a nutrient if intake falls in step with calories, using the 16% and 39% figures above.
| If intake was | After a 16% drop | After a 39% drop |
|---|---|---|
| 100% of the requirement | 84% | 61% |
| 80% of the requirement | 67% | 49% |
| 60% of the requirement | 50% | 37% |
Real intake depends on which foods are cut. The joint advisory's point is that food quality has to rise as quantity falls.2
5. Protein and muscle
| Figure | Detail | Source |
|---|---|---|
| 0.8 g/kg/day | adult Recommended Dietary Allowance for protein | National Academies7 |
| 1.2–1.6 g/kg/day | proposed while body weight is coming down | Joint advisory2 |
| 38% | of the reduction in body weight in one major GLP-1 trial was lean mass (5.3 of 13.6 kg) | Joint advisory,2 trial8 |
| About 20% | of the total is estimated to be muscle | Joint advisory2 |
| 10–15% (women), 20–25% (men) | modeled share that is muscle without structured strength training | Joint advisory2 |
6. Fluid
| Figure | Detail | Source |
|---|---|---|
| 3.7 L / 2.7 L | Adequate Intake for total water a day, men / women, from all food and drink | National Academies9 |
| About 3.0 L / 2.2 L | of that from beverages (about 13 and 9 cups) | National Academies9 |
| About 20% | of daily water normally comes from food, so it falls when food does | National Academies9 |
7. Vitamin B12
| Figure | Detail | Source |
|---|---|---|
| 2.4 mcg | adult Recommended Dietary Allowance | NIH ODS10 |
| None | No upper intake level has been set | NIH ODS10 |
| Two common drug classes | Metformin and acid-reducing medication reduce absorption of B12 from food | NIH ODS10 |
8. What bariatric nutrition guidance adds
Surgical patients are a different population, but they are the best-studied example of what sustained low intake does. The American Society for Metabolic and Bariatric Surgery's micronutrient guideline reports that it is common for patients to have at least one vitamin or mineral deficiency before surgery, and that the prevalence of micronutrient deficiencies is rising while monitoring at follow-up is falling.11 It makes 92 recommendations on screening and supplementation.11
What this report does not show
- It has no original data. Zornava has not surveyed anyone yet. This version will be replaced when our own survey of founding-list members is complete.
- Intake data are from national surveys that predate wide GLP-1 use. They describe the starting point, not people on medication.
- Low intake is not the same as clinical deficiency. A blood test, not a survey, tells an individual where they stand.
- Several sources have industry authors; these are flagged in the list below.
How to cite
Zornava. The Eating-Less Nutrition Gap: what the published data says. Version 1.1. October 11, 2026. https://zornava.com/pages/nutrition-gap
Sources
- RAND Corporation. Research report RRA4153-1 on GLP-1 use in the United States. August 2025. rand.org. Figures as stated in RAND's summary and press release; the full tables were not read.
- Mozaffarian D, et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. Obesity. 2025;33(8):1475–1503. Full text
- Fulgoni VL, et al. Foods, fortificants, and supplements: where do Americans get their nutrients? J Nutr. 2011;141(10):1847–1854. PubMed
- Reider CA, et al. Inadequacy of immune health nutrients: intakes in US adults, the 2005–2016 NHANES. Nutrients. 2020;12(6):1735. PubMed (authors employed by a supplement manufacturer; abstract read)
- US Department of Agriculture and US Department of Health and Human Services. Dietary Guidelines for Americans, 2020–2025. dietaryguidelines.gov
- US Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels. fda.gov
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press; 2005. nap.nationalacademies.org
- Wilding JPH, et al. N Engl J Med. 2021;384(11):989–1002. PubMed
- Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. National Academies Press; 2005. nap.nationalacademies.org
- National Institutes of Health, Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals. ods.od.nih.gov
- Parrott J, et al. American Society for Metabolic and Bariatric Surgery integrated health nutritional guidelines, 2016 update: micronutrients. Surg Obes Relat Dis. 2017;13(5):727–741. PubMed (abstract read)
- PwC. GLP-1 consumer trends in food, apparel and wellness (2026 GLP-1 Usage & Attitudes survey). Published June 22, 2026. pwc.com. Secondary: PwC's page refused automated access on October 11, 2026; the figures are as shown in search-engine excerpts of that page and have not been checked against it.
- Nguyen KP. Coverage of PwC's UK GLP-1 survey. GuruFocus, syndicated by Yahoo Finance, June 22, 2026. finance.yahoo.com. Secondary: press coverage, not PwC's own report.