Your Brain Starts Eating Itself During Marathons. And Other Eye-Popping Headlines.

It’s a beautiful, sunny day in San Francisco. I’m sipping coffee, Sophie is curled up by my side — while, in the background, massive economic dislocation continues to unfold.

[sigh]

Sometimes it’s hard to hold these contrasts: the quiet comfort of morning light alongside the relentless churn of global instability.

In moments like this, I try to return to what grounds me: my body, my community, and the act of connection.

Fall into the arms of those around you.
Be the arms into which others can fall.

These are phrases I’ve been holding onto lately. Because sometimes finding strength and comfort is about letting yourself be held — and offering the same to someone else.

This week, I share 3 nutrition-related stories that caught my attention over the last few days — and comment on them through the lens of a coach and sports nutritionist.

Let’s go.

👇️ 

Headline #1: Your Brain Starts Eating Itself During a Marathon

A recent Nature Metabolism study I saw on Live Science claims marathon running may cause the brain to “consume itself” for energy. While the language is sensational, the research does raise an interesting question: what happens to the brain under extreme physical stress?

In this small study, researchers scanned the brains of 10 marathon runners using MRI 48 hours before their race, then again at 2 days, 2 weeks, and 2 months post-race. The scans focused on myelin, a fatty substance that insulates nerve fibers and helps the brain process signals efficiently.

At the 2-day mark, researchers found statistically significant reductions in myelin water fraction (MWF) in specific brain regions involved in motor control and sensory processing. These localized changes suggest a temporary decrease in myelin content — potentially reflecting the brain’s use of myelin lipids as an emergency energy source during periods of extreme metabolic stress, such as after glucose depletion.

Importantly, by two months post-race, all participants’ myelin levels had returned to baseline, suggesting the brain is highly resilient and capable of recovering from these acute adaptations.

The study says further research is necessary, so it doesn’t quite prove the brain is “eating itself.” 

But it does highlight that extreme effort without adequate energy support may have consequences we’re only beginning to understand.

Fueling Matters

The study also reinforces something much broader and more practical: fueling matters.

When your body runs low on energy — especially during long, high-intensity efforts — it will find a way to keep going. 

That may mean breaking down muscle, pulling from fat stores, or in extreme cases, drawing on structural tissues. That’s not a performance strategy, though. That’s a survival mechanism.

As a coach, I always bring my clients back to three core questions:

• Are you consistently eating enough energy to support training, recovery, and overall health?
  

• Do you have a fueling and hydration strategy in place for longer sessions — including carbs and electrolytes during exercise?
  

• Have you tested that plan in real, event-like conditions to make sure your gut and body respond well?

At the end of the day, this isn’t just about calories. It’s about protecting your nervous system, retaining lean muscle mass, and enabling a consistent training regime.

Headline #2: The More Protein, The Better?

A recent article in The New York Times takes aim at a growing social media narrative that most people — especially women — are dangerously low on protein intake.

You’ve probably seen it: videos claiming you need double or triple the recommended intake to build muscle, lose fat, or even just be “healthy.”

According to national dietary data, though, most Americans — especially men — are already exceeding the current guidelines by 35–55%. So, do you actually need that much protein?

Let’s look at what the research actually says.

Nutrition experts generally recommend 0.8g of protein per kilogram of body weight per day. For a 150-lb adult, that’s about 54 grams — roughly the amount in a single chicken breast.

Some studies suggest that 1.2–2.0g/kg may be beneficial for active individuals, especially those in strength training, endurance, or during weight loss. But beyond that range, the benefits plateau.

And the downsides? 

Excess protein doesn’t build more muscle — it gets broken down, with the nitrogen stripped off and excreted as urea. You’re not getting extra gains. You’re just producing more metabolic waste — and eating more expensive calories.

Total Energy Matters More

As a sports nutritionist, I see protein obsession distract from what first and foremost matters: meeting your total energy needs.

Protein is important. It supports recovery, tissue repair, and lean mass. But there’s a limit to how much your body can use effectively — and when you go far beyond that, you’re often crowding out other nutrient-dense foods.

Here’s how I help athletes think about it:

• Are you hitting your minimum protein needs for your training volume?

• Are you also eating enough fat to support hormones, brain function, and recovery?

• Are you consuming healthy carbs — your body’s preferred training fuel — to take you to your Total Daily Energy Expenditure requirement?

High-protein diets may feel productive, but they’re not magic. And if you’re under-eating overall — which is VERY common — obsessing over protein won’t fix it.

Instead, focus on what actually moves the needle:

• Step 1: Know your TDEE (Total Daily Energy Expenditure) and make sure you’re eating enough to support your goals.
  

• Step 2: Hit your target macros — protein, fat, and carbs — through a balanced, varied diet that includes plenty of fiber-rich whole foods.
  

• Step 3: Distribute your intake throughout the day, with special attention to fueling around your workouts — before, during (if needed), and after — when your body’s demand for nutrients is highest.

#3 The Science Behind Keto

[I hope my husband doesn’t divorce me for this section. He’s currently doing one month of keto. We avoid the subject.]

A recent Science Weekly podcast from The Guardian revisited the ever-trendy ketogenic diet — low-carb, high-fat, and often hyped as a superior strategy for weight loss, cognitive performance, and metabolic health.

Originally developed as a medical intervention for epilepsy, keto remains clinically useful in certain contexts. But for most people using it for weight loss, the mechanism is much simpler: people lose weight because they’re eating fewer calories — not because they’ve unlocked some special fat-burning state.

There’s also an early drop in scale weight, thanks to glycogen depletion and water loss. It’s not fat loss, but it feels like progress — and that quick win can be psychologically powerful.

And for some, keto offers mental relief: clear rules, fewer decisions. But that rigidity is often what makes it unsustainable over time.

Performance and Practicality

Of course, the trade-offs are real.

Carbohydrates are the body’s primary and most efficient fuel source, particularly for high-intensity or endurance training. Some athletes experience a measurable drop in power, stamina, recovery capacity, and mood when carbs are restricted too severely.

The podcast also flagged commonly documented concerns: increases in LDL cholesterol, alterations to the gut microbiome, and difficulty reintroducing carbohydrates after extended restriction.

And practically speaking? Keto is expensive, restrictive, and difficult to sustain — especially if you’re vegan, vegetarian, or training hard. As a coach, I’ve seen more people burn out on keto than build long-term success with it.

My Take

Keto works because it creates a calorie deficit.

And if that’s the goal (i.e. losing weight), there are more effective, sustainable, and less risky ways to get there.

You can build a nutrition plan that is:

• Structured, with enough carbohydrates to fuel high-intensity training and support recovery.

• Nutrient-dense, with a wide variety of fiber-rich, whole foods to promote gut health.

• Flexible, so meals feel satisfying — not restrictive.

All without the physiological risks or long-term trade-offs that often come with keto.

Keto isn’t inherently bad. But it’s not magic.

And for most people — especially athletes — it’s simply not necessary.

As we close, each of these stories is a reminder that fuel matters — not just how much, but when, and in a way that feels sustainable.

You don’t need a fad. You need enough food, in the right balance, to support the way you live and train.

If you need help dialing in your nutrition strategy — or just want to talk through what’s working and what’s not — I’m here.

That’s it for this week.

❤️ Ivan

p.s. here’s a Movement of the Week to check out to stretch the chest muscles.