4 Minute Fridays: The Best Wearable On The Planet (Answer Might Surprise You), This Habit Kills More People Than Obesity & The Best Video I've Seen On Estimating Body Fat %
Feb 13, 2026
Welcome to 4 Minute Fridays, my weekly newsletter, where I reveal cutting-edge tips to help you get lean, boost energy, and live longer.
What's In Store For Today:
- The best wearable on the planet (answer might surprise you)
- This habit kills more people than obesity
- The best video I've seen on estimating body fat
Today's issue is brought to you by High Performance Founder Private Coaching.
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Hey friend,
There was a young samurai named Yuki who dreamed of becoming the greatest warrior in Japan.
He spent years talking about his plans, reading about famous battles, and imagining victory, but when it came time to train, he always had an excuse: the weather wasn't right, he needed to plan more, he wasn't feeling well.
Years passed, and Yuki stayed the same. His ambition hadn't lifted him up; it had made him weaker.
Another warrior, Miyamoto Musashi, became the greatest swordsman in history not through bursts of inspiration but through small, steady actions performed daily.
He had a saying,
"The sword that waits for perfect conditions never leaves its sheath."
Some people wait for motivation before they take action. The ones who succeed take action first and let motivation follow.
Here Is Your 4 Minute Friday:
1. The Best Wearable On the Planet (Answer Might Surprise You)
A collection of 17 studies testing every major wearable against clinical-grade equipment. Apple Watch. WHOOP. Garmin. Oura. Fitbit. Polar.
What did they find? Not a single device wins everywhere. Here's what does.
Best overall sleep tracking: Apple Watch. Best deep sleep detection: WHOOP at 70% sensitivity. Apple Watch was second at 51%. Best HRV for recovery: Oura Gen 4 at about 6% error. WHOOP was second at 8%. Best heart rate during training: Apple Watch at 86%. But a Polar chest strap hits 99%. If you're serious about zone training, spend the $80 instead of arguing over which $400 watch is best. Best step count and VO2 max: Garmin. Best blood oxygen: Apple Watch at about 2% error.
One thing every device gets wrong: calories. The best was only 71% accurate. If you're making food decisions based on your watch, you're building on sand.
Pick the device that matches the metric you care about most. Wear it consistently. Look at trends over weeks, not single readings.
Note: This was summarized from a collection of studies first posted on Reddit. Original post can be found here.
2. This Habit Kills More People Than Obesity
Source: https://ourworldindata.org/lonely-not-alone
Most people worry about their diet, their steps, and their sleep. Almost nobody treats their social life like a health metric. Science says that's a mistake.
A meta-analysis of 148 studies and over 300,000 people found that weak social connections raised the risk of early death by 50%. That's a bigger effect than obesity or physical inactivity.
The U.S. Surgeon General's 2023 advisory put it bluntly: social disconnection carries a mortality impact similar to smoking up to 15 cigarettes a day. That comparison isn't perfectly precise, but the message is clear. Loneliness isn't just emotional. It's physiological.
And it's not rare. Data from Our World in Data shows 30% of Americans over 72 feel lonely at least some of the time. In Greece, it's 62% among older adults.
Chronic isolation raises cortisol, increases inflammation, and disrupts sleep. Your body reads loneliness the same way it reads threat.
Smoking 15 cigarettes a day sounds extreme, but being alone every day sounds normal. That's the scary part. We normalized isolation and call it independence.
We tell our clients all the time that you can train hard, eat clean, and sleep eight hours, and optimize til the cows come home, but if you're isolated, you're leaving one of the biggest longevity levers on the table.
You don't need a huge social circle. You need a few consistent, meaningful connections. A training partner. A weekly dinner. A friend you actually talk to.
❤️ My Favourite Thing This Week
As a fitness coach, I see a wide variance in how people understand body fat percentage and how they estimate their own.
Out of all the videos I've seen on this topic, this one is probably the most accurate.
After looking at hundreds of DEXA scans from our coaching clients, here's what I can tell you: body fat is complicated.
Some people store fat in specific areas. Others gain it evenly across their entire body. Where you store it changes your risk factors. And no two people with the same body fat percentage will look the same.
If you want a better understanding of where you're actually at, this is the video to watch.
Client Of The Week - Tracey, HR Executive
Tracey is an HR executive who wanted to reclaim her health while juggling a demanding career and frequent travel.
She’s now down 24.5 lbs, lost 6.9 inches off her waist, and has made smarter food choices second nature, even during trips and social events. Her workouts and daily steps are now non-negotiable, and her energy and strength levels are the best they’ve been in years.
Here's how we did it:
- Created a flexible eating strategy to support her lifestyle and travel
- Focused on strength training and daily movement as consistent habits
- Empowered her with the tools and accountability to stay on track, anywhere
Tracey didn’t just lose weight, she gained control, confidence, and long-term momentum. Phenomenal work, Tracey!
One Quote To Finish Your Week Strong
“Everyone who has ever taken a shower has had an idea. It's the person who gets out of the shower, dries off, and does something about it that makes a difference.”
― Nolan Bushnell
An idea without action is just a dream.
As promised, get healthier in under 4 minutes.
- Dan
Ps. I've worn every single wearable you can think of. This is the one I've settled on.
When you're ready, here are 2 ways I can help:
1. The Lean Body 90 System: When you’re ready to get in great shape, Lean Body 90 is the obvious choice. You can get in great shape and reach your fitness goals in just 90 minutes a week. Lose weight and build muscle even without hours in the gym or highly restrictive diets. Join 1000+ students here.
2. Are you an entrepreneur who wants to get lean, boost energy, and get in your best shape? Apply for private one-on-one coaching here.
References
- Robbins R, et al. (2024). "Accuracy of Three Commercial Wearable Devices for Sleep Tracking in Healthy Adults." Sensors, 24(20), 6532. DOI: 10.3390/s24206532 — Funded by Oura Ring Inc.
- Dial MB, et al. (2025). "Validation of nocturnal resting heart rate and heart rate variability in consumer wearables." Physiological Reports, 13(16), e70527. DOI: 10.14814/phy2.70527 — Independent (Ohio State / Air Force Research Lab)
- Park et al. (2023). "Accuracy of 11 Wearable, Nearable, and Airable Consumer Sleep Trackers: Prospective Multicenter Validation Study." JMIR mHealth and uHealth, 11, e50983. DOI: 10.2196/50983 — Independent (Korean multicenter)
- Park et al. (2023). "Validating a Consumer Smartwatch for Nocturnal Respiratory Rate Measurements in Sleep Monitoring." Sensors, 23(18), 7867. DOI: 10.3390/s23187867 — Samsung-affiliated authors, Samsung-funded
- Khodr R, et al. (2024). "Accuracy, Utility and Applicability of the WHOOP Wearable Monitoring Device in Health, Wellness and Performance — A Systematic Review." medRxiv. DOI: 10.1101/2024.01.04.24300784
- Oura Internal Validation (2024). Temperature sensor validation study. 16 participants, 93,571 data points. Published on ouraring blog — Oura internal study
- Maijala et al. (2019). "Nocturnal finger skin temperature in menstrual cycle tracking." BMC Women's Health, 19, 150. DOI: 10.1186/s12905-019-0844-9
- Lanfranchi et al. (2024). Samsung Galaxy Watch SpO2 validation. Journal of Clinical Sleep Medicine, 20(9), 1479–1488. DOI: 10.5664/jcsm.11178 — Samsung-affiliated
- WellnessPulse Meta-Analysis (2025). Accuracy of Fitness Trackers — Aggregate data
- AIM7. Smartwatch/Wearable Technology Accuracy — Aggregate validation data
- Christakis et al. (2025). "A guide to consumer-grade wearables in cardiovascular clinical care." npj Cardiovascular Health, 2, 82. DOI: 10.1038/s44325-025-00082-6
- PMC/JAMA (2025). "Selecting Wearable Devices to Measure Cardiovascular Functions in Community-Dwelling Adults." DOI: 10.1016/j.jamda.2025.105529
- Schyvens AM, et al. (2025). "Performance of six consumer sleep trackers in comparison with polysomnography in healthy adults." Sleep Advances, 6(1), zpaf016. DOI: 10.1093/sleepadvances/zpaf016 — Independent (VLAIO-funded, University of Antwerp)
- Caserman P, et al. (2024). "Validity of Apple Watch Series 7 VO2 Max Estimation." JMIR Biomedical Engineering, 9, e54023.
- Lambe RF, et al. (2025). "Validation of Apple Watch VO2 max estimates." PLOS One, 20(2), e0318498. DOI: 10.1371/journal.pone.0318498
- Miller DJ, et al. (2022). "A Validation of Six Wearable Devices for Estimating Sleep, Heart Rate and Heart Rate Variability in Healthy Adults." Sensors, 22(16), 6317. DOI: 10.3390/s22166317
- University of Arizona (2020). WHOOP sleep staging validation vs polysomnography. 89% 2-stage agreement, 64% 4-stage, κ=0.47.
- Loneliness: Holt-Lunstad J, Smith TB, Layton JB (2010) Social Relationships and Mortality Risk: A Meta-analytic Review. PLoS Med 7(7): e1000316. https://doi.org/10.1371/journal.pmed.1000316
Disclaimer: This email is provided for educational and informational purposes only and does not constitute providing medical advice or professional services. The information provided should not be used for diagnosing or treating a health problem or disease, and those seeking personal medical advice should consult with a licensed physician.