What lifters ask about body fat: 10,218 Reddit posts analysed
We read two months of posts from ten fitness and GLP-1 communities to find out what people actually want to know about their bodies. The answer: a body fat number they can trust, and what to do next.
Short answer
In 10,218 Reddit posts from ten fitness and GLP-1 communities (September to November 2026), the most common questions were “should I bulk or cut?” (344) and “what is my body fat?” (331). People increasingly ask AI first, but quoted AI estimates differed by 2 to 8 points and posters asked strangers to check them.
Key findings
- The two biggest questions are “should I bulk or cut?” (344 posts) and “what’s my body fat?” (331). Together they are 56% of all tagged questions.
- r/BulkOrCut alone gets about 83 posts a day, and a quarter of them ask the verdict question in so many words.
- People already ask AI, then ask strangers to check it. We found 22 posts that quoted an AI body fat estimate and still asked Reddit for a second opinion. Where posters quoted two sources, the numbers were 2 to 8 points apart.
- Muscle loss is the quiet worry of weight loss. 158 posts asked whether they were losing muscle, skinny fat or loose skin, concentrated in GLP-1 communities, where such threads drew 40 to 150 comments.
- Weak points are asked about far less than body fat (67 posts), but the question is specific: “how do I find and track muscle imbalances?”
What lifters ask
By community
| Subreddit | Posts | Days | Posts a day | Headline |
|---|---|---|---|---|
| r/BulkOrCut | 1,000 | 12 | 83 | 25% ask bulk, cut or maintain; 10% ask for a body fat guess |
| r/guessmybf | 560 | 58 | 10 | 36% ask for a body fat guess |
| r/progresspics | 1,680 | 59 | 29 | 2% worry about losing muscle; 1.5% ask if there is any change |
| r/Zepbound | 1,000 | 10 | 103 | 5% ask how they look; 1.8% worry about muscle or loose skin |
| r/Semaglutide | 1,000 | 51 | 20 | 1.7% worry about muscle loss; 1.2% ask if it is working |
| r/naturalbodybuilding | 1,500 | 49 | 30 | 1.1% ask bulk or cut; 1.0% ask about weak points |
| r/bodybuilding | 1,478 | 59 | 25 | 1.2% ask about weak points; 1.1% ask for a rating |
| r/Fitness | 1,000 | 36 | 28 | 4.4% ask bulk or cut |
| r/Brogress | 800 | 58 | 14 | 1.1% ask bulk or cut |
| r/GYM | 200 | 6 | 35 | 1.5% ask about weak points |
When AI and people disagree
Asking ChatGPT, Gemini or a phone AI for a body fat estimate is now common, but posters rarely trust the answer. Examples of the gaps they reported:
- Google AI 14% vs ChatGPT 18–20% vs Meta AI 17–18% (r/guessmybf)
- Gemini 12–13% vs ChatGPT 16–17% (r/guessmybf)
- Smart scale 20% vs AI 12% (r/guessmybf)
- Gemini 13% vs ChatGPT 16% (r/BulkOrCut)
- Smart scale 23% vs ChatGPT 21% (r/BulkOrCut)
This matches informal tests of photo-based estimates: errors of several points, and answers that change with lighting, pose, pump and clothing. The practical lesson is not to chase a single number but to measure the same way every time: matched photos, a tape measure and the same scale. Our tape-based body fat calculator is repeatable, and the body fat chart shows what each level usually looks like.
What this means if you’re tracking progress
- Decide bulk or cut from a range, not a guess. The bulk or cut calculator uses common coaching thresholds.
- Judge muscle loss with measurements. If your waist falls faster than your arms and shoulders, you are mostly losing fat. The fat vs muscle loss calculator does the maths from two body fat readings.
- Answer “is there any difference?” with matched photos. Most “can’t tell a difference” posts compare photos taken in different light and poses. A ghost overlay fixes that.
Method
We collected 10,218 public posts from 10 subreddits (listed above) through the Arctic Shift Reddit archive, covering 15 September to 12 November 2026; large subreddits are covered for fewer days because of page limits. Posts were tagged by keyword patterns for each question (for example “bulk or cut”, “guess my bf”, “losing muscle”, “weak points”). A post can carry several tags. Keyword tagging misses some posts and catches a few false positives, so treat counts as directional. The AI examples were read by hand. We quote no usernames and paraphrase rather than copy posts.
Cite as: ProgressLens, “What lifters ask about body fat: 10,218 Reddit posts analysed”, November 13, 2026, https://progresslens.app/research/what-lifters-ask-about-body-fat/
FAQ
Frequently asked questions
What is the most common question lifters ask on Reddit?
In our sample, “should I bulk or cut?” (344 posts), just ahead of “what is my body fat?” (331).
Do people trust AI body fat estimates?
Not really. We found 22 posts quoting an AI estimate that still asked strangers to check it, and quoted estimates from different tools differed by 2 to 8 points.
Can I use this data?
Yes, with a link to this page.