The National Institutes of Health's nih.gov appears in 41.5% of ChatGPT and Gemini answers to fitness questions that cite a source, the strongest lead any single website holds in 12 industries. Government and university websites take 45.5% of fitness citations; forums and social media take 0.2%.
Analysis of 1,600 AI answers to 400 fitness questions · ChatGPT and Gemini, September 2026
Key Findings
- 1.nih.gov is the most-cited website in AI answers to fitness questions, appearing in 41.5% of ChatGPT and Gemini answers that cite a source, the highest top-source share of 12 industries.
- 2.cdc.gov appears in 34.1% of sourced AI answers to fitness questions, nearly three times the 12.3% for the next website, mayoclinic.org.
- 3.Government and university websites take 45.5% of the citations in AI answers to fitness questions, the highest share of 12 industries, and forums, social media and video take 0.2%.
- 4.ChatGPT cites nih.gov in 47.4% of its sourced answers to fitness questions, while Gemini's top source is healthline.com, at 17.6%.
- 5.Gemini answers 80.1% of fitness questions without citing any source, against 1.4% for ChatGPT.
Summary
Someone asks an AI assistant how many minutes of exercise they need a week, or whether to stretch before a run. On ChatGPT, the answer almost always cites the NIH or the CDC. Fitness-specific organisations barely make the list.
For fitness businesses and publishers, that sets the bar. A citation is the link an AI answer shows as its evidence, and it is one of the few ways an answer sends a reader to a website. In fitness, AI engines treat exercise as a health subject and source it from medical research, so fitness brands compete for citations alongside public health guidance.
nih.gov appears in 41.5% of sourced fitness answers and cdc.gov in 34.1%, a concentration no other industry matches. Government and university websites take 45.5% of fitness citations, companies 25.4%, and forums and social media 0.2%.
What we measured
On September 23, 2026 we asked ChatGPT and Gemini 400 fitness questions, each twice, as part of a wider study of AI sources across 12 industries. That gave 1,600 answers, 948 of which cited at least one source, and 461 different websites were cited across them.
A website's share is the percentage of sourced answers that cite it at least once, counting all pages from the same site together. We also sorted every citation by the kind of website behind it: government and education (.gov, .edu and .mil addresses), nonprofits and associations (.org), media and reference publishers, user-generated sites such as forums, social media and video platforms, and companies and other commercial websites. The same measures were taken for the other 11 industries.
The NIH and CDC dominate fitness answers
The top two are federal health agencies: the NIH at 41.5% and the CDC at 34.1%. Hospital systems come next, Mayo Clinic (12.3%) and Cleveland Clinic (10.1%), then the UK's NHS (5.7%) and the health publisher Healthline (5.5%). The American College of Sports Medicine (5.1%) and the American Heart Association (5.1%) are the first organisations that specialise in exercise and heart health.
Source: Suff Digital analysis of 1,600 AI answers to 400 fitness questions · ChatGPT and Gemini, September 2026
| Rank | Website | All answers | ChatGPT | Gemini |
|---|---|---|---|---|
| 1 | nih.gov | 41.5% | 47.4% | 11.9% |
| 2 | cdc.gov | 34.1% | 40.3% | 3.1% |
| 3 | mayoclinic.org | 12.3% | 12.4% | 11.9% |
| 4 | clevelandclinic.org | 10.1% | 9.1% | 15.1% |
| 5 | nhs.uk | 5.7% | 6.5% | 1.9% |
| 6 | healthline.com | 5.5% | 3% | 17.6% |
| 7 | acsm.org | 5.1% | 6.1% | 0% |
| 8 | heart.org | 5.1% | 3.9% | 10.7% |
| 9 | harvard.edu | 3.4% | 2.3% | 8.8% |
| 10 | who.int | 2.6% | 3.2% | 0% |
| 11 | webmd.com | 2.6% | 0.9% | 11.3% |
| 12 | medlineplus.gov | 2.3% | 2.7% | 0.6% |
| 13 | fda.gov | 2.1% | 2.3% | 1.3% |
| 14 | medicalnewstoday.com | 1.9% | 1.3% | 5% |
| 15 | acefitness.org | 1.7% | 2% | 0% |
The list is short as well as concentrated: 461 websites were cited across all fitness answers, the fewest of any industry asked the full 400 questions. The only fitness-specific organisations in the top 15 are the ACSM and the American Council on Exercise's acefitness.org (1.7%). On fitness, AI answers are written from the medical literature, not the gym floor.
ChatGPT and Gemini cite different sites
ChatGPT drives the government lead: it cites the NIH in 47.4% of its sourced fitness answers and the CDC in 40.3%. Gemini cites them in 11.9% and 3.1%, and leans instead on health publishers and hospitals: Healthline (17.6%), Cleveland Clinic (15.1%), WebMD (11.3%) and the American Heart Association (10.7%).
Source: Suff Digital analysis of 1,600 AI answers to 400 fitness questions · ChatGPT and Gemini, September 2026
| Measure | ChatGPT | Gemini |
|---|---|---|
| Answers with no source | 1.4% | 80.1% |
| Websites per sourced answer | 2.2 | 3.6 |
| Most-cited website | nih.gov | healthline.com |
| Share of sourced answers citing it | 47.4% | 17.6% |
Gemini rarely cites at all on this subject. It gives a source in 19.9% of fitness answers, against 98.6% for ChatGPT, so 80.1% of its fitness answers name no website. Across both engines, 40.8% of fitness answers cite nothing. A health publisher has a real chance of being cited on Gemini, but only in the minority of answers that cite anything.
Fitness is the most government-led industry
That is the highest share of the 12 industries, ahead of home improvement at 39.2% and health at 36.2%. Companies and other commercial websites take 25.4% of fitness citations, and user-generated content, meaning forums, social media and video, takes 0.2%, the lowest of any industry. Reddit appears in 0.3% of sourced fitness answers.
Source: Suff Digital analysis of 1,600 AI answers to 400 fitness questions · ChatGPT and Gemini, September 2026
| Industry | Top source | Share of sourced answers | Government and university share | User-generated share |
|---|---|---|---|---|
| Legal | americanbar.org | 14.7% | 20.6% | 3.8% |
| Health | nih.gov | 32.3% | 36.2% | 0.6% |
| Money | irs.gov | 13.8% | 30.2% | 1.7% |
| Real estate | consumerfinance.gov | 27.2% | 26.9% | 1.6% |
| Home improvement | energy.gov | 11.8% | 39.2% | 1.6% |
| Travel | delta.com | 13.2% | 8.1% | 2.8% |
| Cars | consumerreports.org | 6.7% | 11.4% | 2.9% |
| Software | apple.com | 24.3% | 4.7% | 3.2% |
| College | consumerfinance.gov | 13.1% | 32.1% | 2.1% |
| Fitness | nih.gov | 41.5% | 45.5% | 0.2% |
| Pets | vcahospitals.com | 18.4% | 10.1% | 3.1% |
| Recipes | usda.gov | 37.5% | 31.8% | 2.1% |
Fitness is sourced even more heavily from government than health itself: nih.gov's share is 41.5% on fitness questions against 32.3% on health questions. On fitness, AI engines reach for the most official source available.
What this means for fitness brands and publishers
Build on the public health guidance and add to it. Cite the NIH, CDC or ACSM guideline your advice rests on, with a link, and then add what those pages do not give: a full training plan, form cues, progressions for beginners, what a class or session actually involves. A page that pairs the official recommendation with practical, specific detail gives an AI engine a reason to cite you alongside the agency.
Show expertise the way health publishers do: name the qualified author or reviewer, date the page and keep claims specific. On Gemini, where Healthline, Cleveland Clinic and WebMD lead, that is the standard you are measured against. Working with an ai seo company that tracks fitness citations across engines shows which of your pages are cited and which questions go to the agencies instead.
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<p style="font:14px/1.5 system-ui,sans-serif">Source: <a href="https://www.suffdigital.com/resources/data-studies/ai-sources-fitness-questions">AI Answers to Fitness Questions Cite nih.gov 41.5% of the Time, the Top Share of Any Industry - Suff Digital</a></p>
Cite this study
Suff Digital. (2026). AI Answers to Fitness Questions Cite nih.gov 41.5% of the Time, the Top Share of Any Industry. https://www.suffdigital.com/resources/data-studies/ai-sources-fitness-questions
AI Answers to Fitness Questions Cite nih.gov 41.5% of the Time, the Top Share of Any Industry - Suff Digital - https://www.suffdigital.com/resources/data-studies/ai-sources-fitness-questions