Last week, we looked at sleep as the foundation, the thing that services everything else. One thing I didn't mention: poor sleep directly degrades glucose regulation. Which is where we are this week.

Before I get into it, a quick check. Do any of these sound familiar?

Energy that holds through lunch, then drops like a trapdoor around 3 pm. A craving that hits hard and specific - not hunger exactly, more like a demand. Brain fog after a bigger meal. Irritability when a meal runs late, which feels disproportionate. Waking somewhere between 2 and 4 am, mind already running. Afternoons where the focus just isn't there, even when the morning was sharp.

These aren't personality quirks or signs you need more sleep. They're often glucose effects, a signal that blood sugar is less stable than it could be.

For most people, they've become so normalized that they've stopped registering as anything worth addressing aside from adding more caffeine to the day.

There's a concept researchers have called TOFI — thin on the outside, fat on the inside. The idea, building on the literature since the 1980s, is that normal BMI doesn't protect you from the metabolic conditions typically associated with obesity. Body fat percentage matters more than total weight. Where that fat sits matters more than either: visceral fat around the organs versus subcutaneous fat under the skin.

You may have heard this called ‘skinny fat’, an imperfect term that points at something real. Someone can be at a healthy weight and metabolically compromised. Someone can be heavier and metabolically clean.

For people reading this who might feel lean and high-functioning, this isn't abstract. It means you might have less reason to look than you think, and more reason to look than you realize.

I had blood panels done last year. Fasting glucose: 103 mg/dL. HbA1c: 5.7%. Both at the low end of the prediabetes range.

I didn't feel it. Looked fine by any visible measure, maybe not my best, but the panel caught something my body wasn't advertising.

Knowing the number changed what I reached for. I didn't overhaul anything. The awareness created a nudge for urgency I wouldn't have had otherwise. When you don't know the number is elevated, the shortcut is easy to rationalize. The french fries are easier to justify now and then. Once you've seen the numbers, the rationalizations stop working.

Most recent panel: fasting glucose 79, HbA1c 5.6%. Still work to do, but improving towards a clean range.

It’s not specific to dads, but to give myself some grace, this pattern isn't unusual for men in this season of life. A Northwestern University study that followed more than 10,000 men for 20 years found that new resident fathers gained an average of 4.4 pounds after their first child, on top of the weight gain already associated with marriage, while men without children lost an average of 1.4 pounds over the same period.

The sleep disruption, the cortisol load, the dietary drift, it shows up in the numbers. Most men just don't know how to look.

The clinical thresholds for prediabetes exist because they predict disease downstream. But the performance cost starts well before those lines.

Blood sugar instability, even within the normal range, affects energy across the day, cognitive clarity, mood regulation, and sleep quality. Those symptoms in the opening aren't minor inconveniences. They're your system telling you something.

And if you address them, the flip side is real: more consistent energy through the afternoon, fewer cravings that feel like emergencies, sharper focus in the second half of the day, nights that don't break open at 3 am.

The more serious downstream risks are worth knowing about: cardiovascular disease, cognitive decline, and Type 2 diabetes. But for most people here, ideally, the immediate return on getting this right is performance, with a long-term benefit of prevention.

The lever most people underestimate is muscle. Skeletal muscle is the primary site for glucose disposal: it's where blood sugar goes after a meal. More muscle mass means more clearance capacity. This is one reason strength training improves blood sugar independently of diet: you're building the system that handles it.

The dietary levers are less about restriction and more about sequence. Protein and fiber at the start of a meal blunt the glucose spike from whatever comes after.

Movement after meals matters more than most people realize, not because it burns calories, but because muscle contraction pulls glucose from the bloodstream independently of insulin. It doesn't have to be a structured walk. Since having the baby, what that looks like for me is taking out the trash, looping the block with the stroller, or tidying the kitchen. The mechanism doesn't care whether you’re at the gym.

Sleep and stress both drive blood sugar up. Cortisol is glucogenic: it raises glucose as a feature because your body is preparing for a threat. If your nervous system stays elevated, your blood sugar does too. Which is why last week's issue was the foundation.

Kitchen stocked on Sunday. It's become non-negotiable because decisions made when you're hungry and nothing's ready are almost always wrong.

Protein at the start of every meal is a default.

Movement after dinner, whatever the evening allows.

Four workouts this week. The muscle section is key, I'm actively trying to build more of it, and the numbers I shared are part of why.

One tool worth knowing about, especially if you want more than a quarterly snapshot: continuous glucose monitors (CGMs). Several are now available without a prescription. You wear a small sensor on your arm for two weeks and see your blood sugar in real time; how a specific meal moved it, how a workout cleared it, how a bad night of sleep kept it elevated the next morning.

I haven't worn one yet, but I'm planning to. The real-time version of what I described above. Seeing the curve, not just the average.

If you haven't had a blood panel recently and you're over 35, the two numbers worth knowing are fasting glucose and HbA1c, as I understand it. It might be worth taking a look. Not because something is probably wrong, but if there is something quietly working against you, the panel will help you better understand what’s going on.

I'm developing a series called The Stack: nine issues on the physical foundations that compound over time. Sleep was last week. Blood sugar is this week. Each layer connects to the next.

I'm building this as I go, and your feedback shapes where it goes.

Two questions worth hitting reply on:

I read every reply.

The 3 am wake resonated most. Readers also wrote in with what's actually moved the needle. The most practical additions:

One reader built the protein-first sequencing principle into a daily breakfast formula worth stealing:

Around 400 calories total; 50-60 grams of protein, depending on the brand. Fiber and protein are front-loaded before anything else hits. The mechanism described in the letter was made into a meal.

If you've tried something that's moved the needle, hit reply. I'll keep sharing what comes in.

If you missed the previous issue, it's worth going back.

01 — Sleep: The Floor You Keep Lowering
02 — Blood Sugar: The Interior Condition (you're here)
03 — Aerobic Fitness (next week)

See you next Sunday, Eric

P.S. Next week: aerobic fitness. Not cardio as weight management, but as engine capacity. VO2 max is the single strongest predictor of longevity in the medical literature. I'll share my own data and what I found when I actually looked at where my heart rate sits during training.