The Blood-Sugar Rollercoaster of Focus
Eat for steady energy or ride spikes and crashes into brain fog all day.
- Difficulty
- Starter
- Time to result
- ~days to results
- Steps
- 4
- Confidence
- 80%
Drawing on the field of nutritional psychiatry, Hari explains that food directly affects attention. A standard breakfast of sugary cereal or white toast dumps a large, fast hit of glucose into the brain, giving a burst of alertness followed hours later by an energy slump and brain fog — until another sugary snack spikes you again. This puts you on a rollercoaster of spikes and crashes all day. Slow-releasing foods like oatmeal with blueberries deliver steadier energy without the troughs. Hari pairs this with sleep science: the sleeping brain flushes 'brain cell poop,' so too little sleep leaves it clogged and unable to focus.
Origin
For Stolen Focus, Hari interviewed nutritional psychiatrists and British nutritionist Dale Pinnock, who framed modern eating as a rollercoaster of energy spikes and crashes, and sleep scientist Professor Roxanne Prichard, who described how sleep clears metabolic waste from the brain.
Core principles
- 01What you eat directly shapes your ability to focus, via nutritional psychiatry.
- 02Fast-releasing carbs dump glucose quickly, then crash you into brain fog.
- 03Each crash forces another sugary snack, restarting the cycle.
- 04Slow-releasing foods deliver steady energy without spikes and troughs.
- 05Sleep works alongside diet; the brain must clean itself to focus.
How to run it
- 1
Diagnose the rollercoaster
Notice the pattern of a quick post-breakfast high followed by a mid-morning slump and brain fog that only a snack seems to fix.
- 2
Cut the fast-release carbs
Reduce sugary cereals and white toast that release glucose too fast and set up the crash a few hours later.
Watch out Reaching for another sugary snack at the slump just restarts the spike-crash loop.
- 3
Switch to steady-energy foods
Choose slow-releasing options like oatmeal with blueberries that keep energy level and avoid patches of brain fog.
Pro tip Steady glucose means steadier attention across the whole morning.
- 4
Protect your sleep too
Aim for around eight hours so the brain's cerebrospinal fluid can flush metabolic waste and you wake able to focus.
Pro tip Staying awake 19 hours impairs focus as much as being legally drunk.
In the wild
Hari describes eating sugary cereal or buttered white toast, which releases a big fast hit of glucose. He feels alert and ready, but a few hours later at his desk his energy slumps and brain fog sets in, and he can't think until another carby snack spikes him back up.
→ Swapping to oatmeal with blueberries releases energy steadily, removing the spikes and troughs that cause the fog.
Common mistakes
Fixing the slump with more sugar
Another sugary snack spikes you briefly then crashes you again, locking you into the rollercoaster all day.
Ignoring sleep while fixing diet
Chronically sleeping under eight hours leaves the brain clogged with metabolic waste, undermining focus no matter what you eat.
Is it for you?
Best for
Anyone whose concentration crashes mid-morning or mid-afternoon and wants a simple dietary lever.
Not ideal for
People with medical dietary conditions who need individualized clinical nutrition advice.
From the transcript
“The way we eat puts us on a rollercoaster of energy spikes and energy crashes... throughout the day.”
“If you don't get eight hours sleep a night, your brain doesn't get the chance to clean itself fully.”
From the episode
Johann Hari: Stolen Focus, Why You Can’t Pay Attention and How to Think Deeply Again
Johann Hari