Most people discover keto because they want to lose weight.
I discovered something else.
My brain seems to like it.
When I’m eating low-carb consistently, particularly when I combine it with intermittent fasting, I notice something that matters a lot more to me during the workday than whether the scale moved half a pound:
I can think longer without feeling mentally cooked.
My concentration feels steadier.
I’m less likely to experience the afternoon crash.
And when I need to sit down and write, study, prepare a sermon, or solve a problem, I seem to have more sustained mental energy.
That raises an interesting question:
Is there actually something happening in the brain when we switch from primarily burning glucose to producing and using more ketones?
Turns out, there is.
But before I start sounding like the guy at the gym who wants to explain mitochondria to you between sets, let’s make this practical.
Your Brain Is an Energy Hog
Your brain represents only about 2% of your body weight...
yet it consumes roughly 20% of the body's energy at rest.
That's expensive real estate.
And pastors ask a lot of it.
Think about what you may require from your brain in a single day:
You study a difficult biblical text.
You write a sermon.
You switch over to a staff problem.
Then somebody walks into your office with a marriage crisis.
Then you answer 37 emails.
Then you make a budget decision.
Then you remember you haven't written Sunday's announcements.
Then somebody asks if you've “got just a minute.”
You know what that means.
You do not, in fact, have just a minute.
Pastoral ministry requires enormous amounts of executive function...
attention,
working memory,
decision-making,
emotional regulation,
problem-solving...
and the ability to switch rapidly between unrelated tasks.
So I've become increasingly interested in a question we don't ask very often:
What are we fueling the brain with while we're asking it to do all this?
Your Brain Has More Than One Fuel Tank
Under ordinary circumstances, the brain relies heavily on glucose.
Eat carbohydrates, glucose enters the bloodstream, and your body has readily available fuel.
But reduce carbohydrates significantly (or go long enough without eating) and something fascinating happens.
Your liver begins converting fatty acids into ketone bodies, particularly beta-hydroxybutyrate (BHB) and acetoacetate.
Those ketones can cross the blood-brain barrier.
And your brain can use them to make ATP.
(That's the cellular energy currency that keeps your neurons doing neuron stuff.)
This isn't some recently discovered keto hack.
Scientists have known for more than a century that changing fuel metabolism can dramatically affect the brain.
In 1921, Mayo Clinic physician Russell Wilder coined the term ketogenic diet while developing a nutritional treatment for epilepsy.
Our daughter had epilepsy.
Thus, me knowing about keto before it was kool.
The diet was specifically designed to reproduce some of the metabolic effects of fasting.
Johns Hopkins subsequently became one of the major centers studying and using ketogenic therapy for neurological disease.
Think about that.
Keto didn't begin as a beach-body diet.
It began as a brain intervention.
Only much later did somebody apparently realize you could also sell bacon wrapped in cheese on Instagram.
Ketones Aren't Just Emergency Fuel
This is where things get particularly interesting.
Ketones aren't merely calories floating around waiting to be burned.
Research increasingly suggests that ketone bodies also function as signaling molecules and may influence...
mitochondrial function, oxidative stress, inflammation, neurotransmission, and other cellular processes.
In other words, beta-hydroxybutyrate isn't simply gasoline.
It appears to be sending messages under the hood too.
That has researchers interested in ketogenic metabolism for neurological conditions ranging from epilepsy to neurodegenerative disease.
But here's where I want to pump the brakes.
Does that mean keto makes healthy people smarter?
We don't know.
And that's an important distinction.
The evidence that ketogenic therapy can affect the brain is undeniable.
The evidence that putting an otherwise healthy pastor into nutritional ketosis will suddenly turn him into C.S. Lewis is considerably less impressive.
One randomized crossover study put healthy adults into nutritional ketosis for three weeks and compared them with a high-carbohydrate diet.
Researchers found no significant improvement in vigilance, working memory, visual memory, executive function, mood, or sleep.
That's worth knowing.
We shouldn't turn personal experience into settled science.
But newer research makes the story more interesting.
The Newer Data Are Intriguing
A 2026 study examined more than 100 sedentary healthy adults ages 25–45.
After four weeks, those assigned to a ketogenic diet showed improvements in several measures, including processing speed, working memory, episodic memory, semantic memory, and overall cognitive scores compared with controls. (PubMed)
Interestingly, attention and cognitive flexibility did not significantly improve.
Other experiments have bypassed the ketogenic diet altogether and simply elevated ketones with ketone esters.
In adults with obesity, two weeks of beta-hydroxybutyrate supplementation increased cerebral blood flow and produced improvements on some cognitive tests. (PubMed)
And researchers have found something particularly relevant to productivity:
Ketones may become more interesting when the brain is under stress.
A 2024 randomized crossover study involving military personnel exposed participants to severe simulated altitude.
Ketone supplementation helped attenuate the decline in cognitive performance under those stressful conditions. (PubMed)
Another study found that ketone supplementation helped preserve aspects of executive function following exhausting exercise. (PubMed)
And a small 2026 randomized crossover study of 25 healthy adults found that a ketone monoester helped prevent some deterioration in cognitive performance after experimentally induced mental fatigue. (PubMed)
Now you've got my attention.
Because I'm not particularly interested in whether ketones help me perform a computerized memory test while sitting peacefully in a laboratory.
I'm interested in what happens at 3:17 Thursday afternoon after I've already made 40 decisions and still need to write something requiring my best thinking.
That's the productivity question.
But There's Another Explanation We Shouldn't Ignore
There's something else happening when I eat low-carb that may be just as important as ketones themselves.
I'm not riding the glucose roller coaster.
Most of us have experienced this.
You eat the giant plate of pasta at the church lunch.
Add the roll.
Someone's grandmother made banana pudding, and refusing it would obviously damage church unity.
An hour or two later, you don't need another productivity hack.
You need a couch.
A lower-carbohydrate eating pattern generally produces smaller post-meal glucose excursions than a high-carbohydrate meal.
And regardless of whether ketones themselves are giving me some cognitive superpower, avoiding enormous swings in blood sugar and the accompanying post-meal sluggishness can make the workday feel dramatically different.
That's an important distinction.
Maybe some of what people call “keto clarity” isn't the brain suddenly operating on rocket fuel.
Maybe part of it is simply:
I stopped putting myself into a food coma every afternoon.
Either way, I'll take it.
The Science Is Promising—But Not Settled
A recent systematic review and meta-analysis looked at 30 randomized controlled trials involving 1,781 adults and found no overall significant improvement in memory speed from low-carbohydrate diets. Results varied considerably among populations and interventions. (PubMed)
So here's where I land:
The evidence isn't strong enough to say, “Go keto and your brain will work better.”
It is strong enough to say that ketones are a legitimate alternative brain fuel with interesting neurological effects, and emerging research suggests they may influence cognitive performance under certain circumstances.
That's much more interesting than the hype anyway.
Because optimization isn't about finding one weird trick that turns you into a productivity machine.
It's about experimentation.
Here's the Experiment I'd Try
You don't have to buy ketone drinks.
You don't have to calculate your beta-hydroxybutyrate level every 17 minutes.
And you definitely don't need to start telling strangers that you're “metabolically flexible.”
Just run an experiment.
For two weeks, reduce the refined carbohydrates and sugars that dominate the typical American diet.
Build meals primarily around:
Protein + healthy fats + fibrous vegetables.
Eggs.
Beef.
Chicken.
Fish.
Avocado.
Olive oil.
Nuts.
Non-starchy vegetables.
Keep the bread, pasta, potatoes, rice, desserts, and sugary drinks low enough that you're substantially reducing your carbohydrate load.
If you already practice intermittent fasting, that's another natural way to spend more time with lower insulin and increased fat oxidation.
Then don't merely watch the scale.
Watch your brain.
For two weeks, rate these four things every afternoon from 1–10:
Mental clarity.
Ability to concentrate.
Energy stability.
Food cravings/hunger.
And pay particular attention to the hours when you do your most cognitively demanding work.
Sermon preparation.
Writing.
Strategic planning.
Problem-solving.
Don't ask, “Am I in ketosis?”
Ask:
“Am I producing better work?”
That's the metric that matters.
Protect Your Best Brain Hours
There's another practical implication here.
Even if you never eat a ketogenic diet, you can become more intentional about what you eat before cognitively demanding work.
If Tuesday morning is sermon-writing time, don't precede it with pancakes, syrup, orange juice, and a cinnamon roll.
You may have just scheduled a meeting between the Holy Spirit and your pancreas.
Experiment with a high-protein, lower-carbohydrate breakfast...
or simply continue your overnight fast if that works well for you.
Then schedule your hardest cognitive work during the window when your brain feels sharpest.
That's optimization.
Not squeezing more activity into the day.
Matching your physiology to your priorities.
Your Ministry Runs Through Your Brain
We tend to separate spiritual ministry from physical biology more than Scripture does.
Your brain is part of the body God gave you.
The sermon you preach travels through neurons.
The decision you make requires glucose, ketones, oxygen, neurotransmitters, and ATP.
Your ability to patiently listen to a hurting church member depends partly on whether your prefrontal cortex still has something left in the tank.
None of that makes ministry less spiritual.
It reminds us that stewardship is holistic.
Paul told Timothy:
“Train yourself for godliness. For the training of the body has limited benefit, but godliness is beneficial in every way...”
—1 Timothy 4:7–8
Notice that Paul didn't say bodily training had no value.
He said its value was limited compared with godliness.
So I'm interested in both.
I want to steward my spiritual life.
And I want to steward the physical machinery through which I'm going to study, think, write, lead, preach, and serve.
If changing what I put on my plate helps me bring a clearer brain to that calling, that's worth knowing.
Maybe fat loss isn't the only reason to teach your body to burn fat.
Maybe one of the biggest benefits is what happens upstairs.
More Resources To Help You Optimize
💊 My (Scott's) full supplement regimen