“My child studies, but their grades just aren’t improving…”
“Is there really a link between diet and academic performance?”
“I’ve heard childhood obesity can affect brain development too. What does that actually mean?”
More and more parents have been asking questions like these lately.
The truth is, many studies have shown a deep relationship between children’s eating habits and their academic performance.
Brain development, concentration, and memory are all heavily influenced by “what your child eats.”
In this article, I’ll explain the connection between eating habits and academic performance from a scientific perspective, and share concrete changes to children’s eating habits that parents can make starting today.
- 1 The Scientific Reasons Childhood Obesity and Eating Habits Are Directly Linked to “Academic Performance”
- 2 How Childhood Obesity Leads to Lower Academic Performance
- 3 Risky Eating Patterns That Drag Down Children’s Grades
- 4 Changes to Children’s Eating Habits Parents Can Make Right Now
- 5 What Parents Should Keep in Mind When Worried About Their Child’s Weight
- 6 Frequently Asked Questions About Childhood Obesity, Eating Habits, and Academic Performance
- 7 Eating Habits That Protect Your Child’s Brain and Body: What You Can Change Starting Today
The Scientific Reasons Childhood Obesity and Eating Habits Are Directly Linked to “Academic Performance”
Study time isn’t the only thing that shapes a child’s grades.
Recent research in nutritional neuroscience has been revealing, one finding after another, that eating habits directly affect brain development, concentration, and memory.
In particular, “what they eat” is just as important a factor as “how much they study.”
The Brain Is “an Engine That Burns a Lot of Fuel”
The brain is one of the most energy-hungry organs in the body, and a growing child’s brain needs even more nutrition than an adult’s.
Think of it this way: the brain is a high-performance engine, and food is the gasoline you put into it.
If you fill it with poor-quality gasoline, or fill it up at random times, the engine won’t run smoothly.
Whether a child can focus on studying also depends on “what kind of fuel goes in, and on what kind of rhythm.”
Nutrients the Brain Needs to Develop
A child’s brain is developing rapidly, and getting enough of certain nutrients is directly tied to intellectual development.
DHA, iron, zinc, and the B vitamins are essential for building the brain’s neural circuits, producing neurotransmitters, and locking in memories.
| Nutrient | Main Foods | Effect on the Brain and Academic Performance |
|---|---|---|
| DHA / EPA | Mackerel, sardines, salmon, flaxseed oil | Forms the membranes of nerve cells; boosts memory and learning efficiency |
| Iron | Red meat, liver, spinach, short-neck clams | Supplies oxygen to the brain; maintains concentration and cognitive function |
| Zinc | Oysters, beef, cashews, pumpkin seeds | Nerve signaling, locking in memories, brain repair |
| B vitamins | Eggs, pork, natto (fermented soybeans), brown rice, nuts | Synthesis of neurotransmitters, energy metabolism, concentration |
| Choline | Egg yolks, soybeans, liver | Raw material for acetylcholine, which is involved in memory |
| Dietary fiber | Vegetables, beans and legumes, seaweed, whole grains | Calms inflammation in the brain through the gut-brain connection and protects cognitive function |
The “Rhythm” of Eating Matters More Than “How Much”
Even when they eat the same amount, a child who skips breakfast and eats a lot at night and a child who eats three meals at roughly set times are said to tend to differ in how well they concentrate during the day.
When mealtimes are consistent from day to day, the body clock gets regulated, and bedtimes and wake-up times tend to become more stable too.
Blood Sugar Spikes Steal Concentration
Eating mostly soft drinks, sweets, and sweet buns causes “blood sugar spikes,” in which blood sugar shoots up and then plunges.
This roller coaster of blood sugar causes drowsiness, poor concentration, irritability, and weaker memory, dragging down performance in class dramatically.
If your child says “after eating, nothing in class sinks in,” blood sugar spikes may be the cause.
How Childhood Obesity Leads to Lower Academic Performance
People tend to think of obesity as simply a matter of “eating too much,” but childhood obesity also has a direct effect on brain function.
Let’s look at how that works.
Obesity Interferes With Development of the Frontal Lobe
An analysis of the large U.S. ABCD Study (ages 9 to 11, about 2,700 children)
reported a tendency for children with higher BMI to have thinner cortex in the prefrontal cortex (the region in charge of executive function, planning, and judgment) and lower executive function scores.
However, this is a point I want to state accurately.
This is a cross-sectional study (an observation at a single point in time), so it cannot establish cause and effect, as in “obesity changed the brain.”
- The researchers themselves raise the possibility of the reverse direction, that “weaker executive function affects BMI through eating behavior,” as well as the possibility that genetic and environmental factors influence both.
- In fact, another study showed that socioeconomic factors such as household income and neighborhood living conditions are involved in both BMI and brain development, so it isn’t a simple matter of cause and effect.
Even so, it’s certain that the prefrontal cortex is a region deeply involved in concentration, emotional control, and learning efficiency, so that doesn’t take away the value of getting eating habits in order.
Don’t Assume “My Child’s Grades Are Bad Because They’re Overweight”
As a parent, it’s important not to jump to the simple conclusion that “my child’s grades are bad because they’re overweight.”
With that in mind, think of a diet and daily rhythm that support brain development as a plus for every child, whatever their body type.
Please try the tips in this article not as a way “to make your child lose weight,” but as a way “to help their brain and body grow up healthy.”
The Damage Chronic Inflammation Does to the Brain
When overeating and a steady diet of ultra-processed foods create chronic inflammation in the body, that inflammation spreads all the way to the brain.
Inflammation in the brain (neuroinflammation) makes nerve cells less efficient at transmitting signals, lowering memory, processing speed, and the ability to learn.
Improving eating habits helps protect a child’s brain.
I also explain how overeating affects the gut environment and immunity in detail in another article, so please take a look.
Poorer Sleep, Less Exercise, and Lower Confidence Also Affect Academic Performance
The ways childhood obesity is linked to academic performance aren’t limited to direct effects on the brain.
- As weight goes up, sleep quality can drop, with snoring or waking up several times during the night.
- When a child feels heavy and starts avoiding outdoor play and exercise, it also becomes harder to get the mood boost and better focus that come from moving the body.
- On top of that, being teased about their body can cause a child to lose confidence and lower their motivation for school life and studying.
In other words, it’s important to see childhood obesity and academic performance as an issue of “the whole lifestyle,” where diet, sleep, exercise, and emotional state are all intertwined.
Risky Eating Patterns That Drag Down Children’s Grades
Let’s go over the eating patterns that are especially problematic.
- Skipping breakfast, or a carbs-only breakfast
- A steady diet of ultra-processed foods and soft drinks
- The habit of late-night eating and packaged snacks
- “Mindless grazing” while gaming or looking at a phone
Skipping Breakfast, or a Carbs-Only Breakfast
Children who go to school without eating breakfast run short of brain energy in the morning, and their concentration and grades suffer.
But it’s not as simple as “just eat breakfast”: a breakfast of nothing but sweet buns, sugary cereal, and soft drinks causes blood sugar spikes and actually robs children of concentration.
A breakfast that includes protein (eggs, natto (fermented soybeans), cheese) is what supports a child’s concentration.
A Steady Diet of Ultra-Processed Foods and Soft Drinks
When convenience-store snacks, instant noodles, and soft drinks have become everyday meals, children are chronically short of the DHA, iron, zinc, and B vitamins needed for brain development.
These nutrients are essential for producing neurotransmitters, and when they’re lacking, children easily end up in a state where, even when they study, “it doesn’t stick” or “they can’t understand it.”
The Habit of Late-Night Eating and Packaged Snacks
Snacks before bed and mindless munching while gaming lower the quality of sleep.
When the memory consolidation and brain repair that happen during sleep are disrupted, learning efficiency the next day drops sharply.
Some observational studies show a link between late-night eating habits and school grades, but because the whole lifestyle is involved, you can’t say late-night eating alone is the cause.
“Mindless Grazing” While Gaming or Looking at a Phone
When children eat while looking at a screen, it’s hard for them to notice how much they’ve eaten, and hard to feel the signals that they’re full.
Plenty of adults have had the experience of realizing they’ve finished an entire bag of snacks without noticing, too.
Mindless grazing not only leads to overeating; reaching for snacks again and again in the middle of homework also makes it easier for concentration on studying to break.
It’s a good idea to set a family rule that snacks are eaten at the table, at a set time and in a set amount.
| Eating Habit | Effect on the Brain and Concentration | Academic Risk |
|---|---|---|
| Breakfast of eggs, natto (fermented soybeans), or fish | Stable blood sugar; replenishes neurotransmitters | ↓ Lower |
| Vegetables and fermented foods at every meal | Balances the gut-brain connection and curbs inflammation in the brain | ↓ Lower |
| Switching snacks to nuts, fruit, or cheese | Prevents blood sugar spikes and maintains concentration | ↓ Lower |
| Breakfast of sweet buns and soft drinks | Blood sugar spikes → drowsiness, poor concentration | ↑ Higher |
| A steady diet of ultra-processed foods | Lack of DHA, iron, and zinc → weaker memory | ↑ Higher |
| Late-night eating and snacks before bed | Lower sleep quality → memory consolidation disrupted | ↑ Higher |
Changes to Children’s Eating Habits Parents Can Make Right Now
In some ways, improving eating habits shows results more readily in children than in adults.
A developing brain has high plasticity (the ability to change), so when eating habits change, differences start to appear within a few weeks to a few months.
What Changes When You Simply Improve Breakfast
Just switching a breakfast of “white rice or bread + a sweet drink” to “eggs, natto (fermented soybeans), or cheese + vegetables + water or tea” makes a big difference in morning concentration.
Adding protein and fat to breakfast makes blood sugar rise more gently, which keeps performance in class steady.
This is the reason behind reports like “since we changed breakfast, my child doesn’t get sleepy in class anymore.”
| Breakfast before | Breakfast after the change | |
|---|---|---|
| What’s on the plate | White rice or bread + a sweet drink | Eggs, natto (fermented soybeans), or cheese + vegetables + water or tea |
| Blood sugar | Prone to blood sugar spikes | Rises more gently |
| During class | Robs children of concentration | Performance stays steady |
Put Brain-Building Foods on the Table Every Day
Make oily fish (DHA/EPA), eggs (choline, iron), nuts (zinc, vitamin E), and dark green and orange vegetables (iron, B vitamins) a regular part of meals.
- Oily fish (DHA/EPA)
- Eggs (choline, iron)
- Nuts (zinc, vitamin E)
- Dark green and orange vegetables (iron, B vitamins)
These are the “raw materials for the brain,” and eating them steadily every day strengthens the brain’s neural circuits.
If processed foods have become the staples in your home, I’d like you to start by putting these foods on the table at least three times a week.
Think of Snacks as “a Small Fourth Meal”
Growing children can’t always get all the nutrition they need from three meals alone, so snacks are really meant to play the role of a “small meal” that fills in nutrition.
Seen that way, it’s clear that onigiri (rice balls), fruit, yogurt, cheese, and yaki-imo (roasted sweet potato) are better suited than packaged snacks or sweet juice.
Having snacks once a day at a set time, in an amount that won’t spoil dinner, also keeps the rhythm of meals from getting thrown off.
Eat Together and Cook Together as a Family
Children pick up eating habits far more easily when parents “do it together” with them than when parents “tell them what to do.”
When the family sits around the same table, children naturally start imitating how their parents eat.
It’s also a good idea to go shopping together on days off and pick out vegetables, or ask them to help with simple tasks like cracking eggs or tearing up vegetables.
When children have had a hand in a dish, they’re more likely to feel “I’ll try one bite,” even with foods they don’t like.
I also explain the relationship between insulin resistance and blood sugar spikes in another article, so please take a look.
What Parents Should Keep in Mind When Worried About Their Child’s Weight
When you’re worried about your child’s body shape or grades, it’s natural to feel pressured to “fix it quickly.”
But unlike adults, children’s bodies are still growing, so applying the same methods adults use to them can be dangerous.
Don’t Put Children on Restrictive Diets or Fasts
Growing children need lots of nutrition to build their bones, muscles, and brains.
If you drastically cut how much they eat during this period, or have them do fasting the way adults do, they may end up short of even the nutrients they need to grow.
The idea of “time without eating” introduced on this blog is meant for adults, so don’t have children fast; make eating three proper meals a day the foundation.
The basic approach to childhood obesity is considered to be not losing weight quickly, but improving the quality of meals and daily rhythms so that children don’t gain too much weight while they’re growing taller.
Don’t Blame Your Child for Their Body Shape or Grades
Saying things like “you can’t study because you’re overweight” can hurt a child deeply.
Worrying too much about body shape can also lead to unreasonable dieting or guilt about eating.
When you talk to your child, choose words that focus on positive actions, like “I hear eating vegetables helps clear your head” or “Want to go for a walk together?”
| Words to avoid | Words to choose |
|---|---|
| “You can’t study because you’re overweight” | “I hear eating vegetables helps clear your head” “Want to go for a walk together?” |
| Blaming your child for their body shape or grades | Focusing on positive actions |
Set Up Time for Physical Activity and Sleep as Well
When it comes to childhood obesity, time spent moving and sleep matter just as much as diet.
Exercise doesn’t have to mean a particular sport; anything that lets them move their bodies and have fun is fine, such as playing outside, riding a bike, or going for family walks.
Just setting limits on gaming and phone time at night, and cutting back on screens and late-night snacks before bed, can help improve sleep quality and appetite the next morning.
If You’re Concerned, Talk to a Pediatrician
School health checkups in Japan use a measure called the “obesity index,” which shows how far a child’s weight is above the standard weight for their height, and an obesity index of 20% or more is used as a guideline for obesity.
If a checkup has flagged your child as obese, or if they’ve suddenly gained weight, snore heavily, or tire easily, consult your family pediatrician.
- A checkup has flagged your child as obese
- They’ve suddenly gained weight
- They snore heavily
- They tire easily
Rather than trying to handle it all at home, working out a manageable plan together with a professional is the quickest way to protect your child’s body and mind.
Frequently Asked Questions About Childhood Obesity, Eating Habits, and Academic Performance
Trying to change everything at once often makes children push back, so start by changing just one thing.
Simply “switching soft drinks to water or tea” reduces blood sugar spikes and leads to better concentration.
Once children can feel the difference for themselves, their attitude toward food naturally starts to change.
It’s more important to teach them to “choose” than to “quit.”
By choosing cheese, nuts, bananas, boiled eggs, and the like as snacks instead of soft drinks and packaged snacks, they can get nutrients while avoiding too much sugar.
Suggesting “this one is better for your body” gets through to children more easily than “you’re not allowed to eat that.”
Rather than asking “which is more important,” it’s more accurate to see it as “eating habits lay the foundation for learning efficiency.”
When the brain is well nourished, a child can absorb more in the same amount of study time.
I’d like you to think of improving eating habits as “laying the foundation,” something to work on alongside cram school.
A breakfast that’s small but high in protein works well.
One boiled egg, one slice of cheese, a small pack of natto (fermented soybeans): even just this has a far better effect on the brain than “carbs only” or “skipping breakfast.”
Preparing it the night before saves time in the morning, which makes it easier to turn into a habit.
Deliberate fasting is not recommended for growing children.
However, as long as they eat three proper meals a day, avoiding all-day grazing and leaving a reasonable gap between meals helps stabilize blood sugar and improve the gut environment.
I explain the basics of fasting in detail in another article, so please use it as a reference for improving adults’ eating habits.
Eating Habits That Protect Your Child’s Brain and Body: What You Can Change Starting Today
Changing a child’s eating habits not only raises their grades but also helps build the foundation for lifelong health.
The “quality of nutrition” that reaches the brain determines whether a child’s potential expands or shrinks.
3 Eating-Habit Improvements to Start Today
- Add one protein food to breakfast
Add eggs, natto (fermented soybeans), cheese, or yogurt to breakfast every morning. This alone makes blood sugar rise more gently and keeps morning concentration steady. Swapping out sweet buns and soft drinks is the first step - Switch soft drinks to water, mugicha (roasted barley tea), or green tea
Drinks are a major source of blood sugar spikes throughout the day. Just quitting soft drinks greatly reduces chronic damage to the brain. If your child resists, it’s fine to dilute them at first - Serve oily fish and dark green and orange vegetables at least three times a week
Canned mackerel and canned sardines are an affordable way to get DHA. Dark green and orange vegetables such as spinach, carrots, and broccoli provide iron, B vitamins, and folate. Small, steady habits strengthen the brain’s circuits
And along with eating habits, work on “early to bed, early to rise” and “time for physical activity” as a set.
The simple rhythm of sleeping well, moving well, and eating properly creates the environment where a child’s brain can perform at its best.
There’s no need to aim for perfection, so try bringing in one thing at a time, starting with whatever the whole family seems able to do.
Changing what’s on the table is the same as changing your child’s future.
I’d like you to start with today’s meal by making a point of including protein and fat.
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