Sleep quality, hidden muscle fat + a better IUD experience

Sunday · 7:44 AM ET · Better Habits. Healthier Habitat.

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Every 7 days, we begin here with 4x4 box breathing.

Soften your jaw. Let your tongue relax from the roof of your mouth. Drop your shoulders. Take one round, or stay for a few until you feel grounded.

Inhale 4 sec · Hold 4 sec
Exhale 4 sec · Hold 4 sec

Welcome back to The Nest
Summer officially hands things over to fall this week. Shorter days, cooler mornings, and a natural moment to reset the habits we carry into the rest of the year.

A line to carry
“How you live today is how you live your life.”
(Submitted by Dr. Jocelyn Cohen)

In today’s digest, we’ll be discussing:

A massive new study suggests REM, deep sleep, consistency, and nighttime wakefulness may matter alongside total hours. For years, sleep advice has centered on one number: how many hours did you get? But a new PLOS Medicine study followed 95,559 adults using wrist-worn accelerometers and looked at much more than duration. Researchers estimated REM, deep and light sleep, nighttime wakefulness, and sleep irregularity, then followed participants for a median of 8.9 years to see how those patterns related to future health. Greater REM and deep sleep were associated with lower risk across multiple conditions, while fragmented and irregular sleep patterns were associated with higher risk.

There was another interesting finding: for most of the conditions tied to sleep duration, the lowest risk clustered around six to eight hours. That does not mean everyone should suddenly aim for six hours, and the study cannot prove that changing your sleep stages prevents disease. But it does suggest that two people can both log “eight hours” while experiencing very different nights underneath that number. Your Oura, Apple Watch, or Whoop is not a diagnostic tool, but the obsession with sleep stages may not be completely misplaced.

Takeaway: Don’t just chase a perfect number. Enough regular, uninterrupted sleep may give your body the best chance to move through the stages it needs.

We usually think about body fat as something stored around the waist, hips, or under the skin. But researchers studying 615 adults found something less visible. People who ate a greater share of ultra-processed foods tended to have more fat infiltrating the muscles of their thighs. The association remained even after researchers accounted for total calorie intake, physical activity, smoking, and other factors. The finding resurfaced in health news this week through new coverage of the Radiology research.

That matters because fat inside muscle is different from the body fat we can see in the mirror. Higher muscle-fat infiltration can be a marker of poorer muscle quality, and the researchers are particularly interested in whether it could affect the support muscles provide around the knee. There is an important limitation: this was an observational snapshot of people already considered at risk for knee osteoarthritis, so it cannot prove that ultra-processed food caused the muscle changes. Still, it adds another layer to the idea that food quality may matter in ways a calorie count cannot capture.

Takeaway: Calories tell you how much energy is in your food. They do not tell you the whole story about diet quality or what may be happening inside your tissues.

A simple, needle-free anesthetic significantly reduced insertion pain in a new randomized trial. If you have ever heard IUD insertion described as “just a pinch,” this study is worth knowing about. In a new JAMA randomized clinical trial of 370 people who had never given birth, clinicians used a thin catheter to place a local anesthetic called mepivacaine directly inside the uterus before inserting the IUD. Average pain during placement was 43.8 out of 100 with the anesthetic, compared with 58.6 with placebo.

Even more telling, 98.3% of participants receiving mepivacaine described their pain as tolerable, compared with 91.4% in the placebo group. This was not painless, and the researchers did not compare the technique against every other available pain-management option. But it is simple, does not require an injection into the cervix, and could give women another evidence-based option to discuss before their appointment.

Takeaway: Pain control is becoming a more concrete part of the IUD conversation, and this may give women one more option to ask about before insertion.

Which statement about “pasture-raised” eggs is most accurate?

A. USDA requires every pasture-raised hen to have at least 108 square feet of outdoor space

B. Pasture-raised is a federally standardized term that guarantees more outdoor access than free-range

C. Pasture-raised standards can vary by certifier, so the label alone does not guarantee one universal amount of outdoor space

D. Pasture-raised eggs must contain more omega-3s and vitamin D than cage-free eggs

Answer below ↓

Three short workouts a week produced measurable changes in mood and biology, even while memory scores barely moved. Researchers took 52 relatively inactive adults ages 45 to 65 and randomly assigned them either to continue their normal routines or complete a 12-week exercise program. The workout group did just three 30-minute online sessions per week, mixing high-intensity cardio, resistance training, and functional exercise. In the NeuroFit randomized trial, researchers were specifically looking for improvements in a type of memory linked to the hippocampus. They did not find a significant improvement after three months. But something else happened.

Depressive symptoms decreased in the exercise group, even though participants were not depressed to begin with. Researchers also took blood samples from the participants and exposed human hippocampal progenitor cells to that serum in the lab. After the exercise program, the blood altered how those cells behaved, suggesting that regular movement had changed the circulating biological environment even though cognitive test scores had not yet caught up. The researchers think different benefits may simply emerge on different timelines.

Takeaway: Not every benefit of exercise shows up immediately on a test. Your mood and underlying biology may begin adapting before you notice a change in memory or mental sharpness.

⌚ ★ Apple Watch is officially coming for the recovery-score crowd. The new Series 12 adds a daily Readiness score, Health Age, higher-frequency HRV tracking, and an AI-powered Health app that explains what your data may actually mean.

🐕 ★ Your dog is entering the wearable era too. New pet wearables are moving beyond GPS to monitor activity, behavior, barking, routines and health, while AI-powered collars are beginning to translate changes into plain-language insights for owners. The broader pet-wearable market is projected at about $3.2 billion in 2026.

🥩 ★ Protein has become very, very big business. The company behind David Protein just raised $250 million at a reported $2.25 billion valuation and plans to push the high-protein brand into even more food categories.

🔥 ★ Sauna culture now has its own competitive sport. Aufguss turns sauna sessions into choreographed performances with music, essential oils, costumes and elaborate towel work, complete with U.S. nationals and world championships.

🚿 Red light therapy has officially reached the shower. HigherDOSE now sells a $599 showerhead combining filtered water with red and near-infrared light, another sign that recovery tech is moving from dedicated devices into everyday home routines.

Clinical health psychologist + sleep specialist

Dr. Daniella Marchetti looks at sleep from a slightly different angle. Instead of treating better sleep as a collection of hacks, supplements, and perfect nighttime routines, she focuses on the psychology of sleep and what can actually keep us awake in the first place. She is a licensed psychologist and Diplomate in Behavioral Sleep Medicine whose work centers on insomnia, behavioral sleep medicine, and evidence-based approaches like Cognitive Behavioral Therapy for Insomnia, or CBT-I. A lot of her content is especially relatable for anyone who has ever been exhausted all day, only to suddenly have a very awake brain the second their head hits the pillow. She talks about racing thoughts, sleep anxiety, trying too hard to sleep, nighttime awakenings, and the habits that can quietly make insomnia worse, all with a realistic approach that focuses on understanding what is happening rather than obsessing over perfect sleep.

Why follow: For thoughtful, science-backed sleep advice that goes deeper than “avoid your phone before bed” and helps you understand the relationship between your thoughts, behaviors, and sleep.

Follow her here:

Instagram @drdaniellamarchetti ↗
Website daniellamarchetti.com ↗
Substack - Sleep Talking ↗

C. Pasture-raised standards can vary by certifier.

Unlike “cage-free” and “free-range,” pasture-raised does not represent one universal federal outdoor-space requirement across every carton. For USDA-grademarked eggs using terms such as “pasture raised,” USDA requires verification through a recognized third-party certification program, but the specific pasture standards can differ between certifiers.

Try this week:
Check your egg carton for the actual certification behind “pasture-raised,” not just the words on the front.

Fruit
🍎 Apples · 🍐 Pears · 🍇 Grapes · 🍑 Peaches · Plums · 🍉 Watermelon · Raspberries

Vegetables
🍅 Tomatoes · 🌽 Sweet corn · 🫑 Bell peppers · 🍆 Eggplant · 🥒 Cucumbers · Green beans · Zucchini · Summer squash · 🎃 Winter squash · 🥦 Broccoli · 🥕 Carrots · 🥬 Kale · Beets · 🧅 Onions · 🌿 Fresh herbs

_{Seasonal availability may vary by region and growing conditions.}

If this brought a little calm or clarity to your Sunday morning, send it to someone who would appreciate it too.

If this week’s quote resonated with you, reply with one of your favorites.

We’ll choose one reader submission for next week’s line to carry.