Real science, no lectures. Every card has a fact, a thing you can actually try today, and where the fact comes from — so you know it's true.
The basics: water, moving, plates, sleep.
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About 60% of your body is water. Your brain is even wetter — around 73%. When you don't drink enough, your brain gets tired and grumpy before your body does.
Source: NHS Eatwell / U.S. Geological Survey water science
One 500ml bottle of fizzy drink can hold around 13 teaspoons of sugar — but it doesn't make you feel full, so your body asks for food anyway.
Source: NHS Change4Life sugar guidance
Kids need about 60 minutes of moving each day — but it counts in bits. Walking the dog, dancing in your room and playing tag all add up.
Source: World Health Organization physical activity guidelines, 5-17 years
Filling half your plate with vegetables and fruit means you can still enjoy the rest — you just get more vitamins and fibre with it.
Source: NHS Eatwell Guide
When you sleep less than about 9 hours, your body makes more of the 'I'm hungry' hormone and less of the 'I'm full' one. Tired days really do feel hungrier.
Source: American Academy of Sleep Medicine, 6-12 years: 9-12 hours
Muscle burns energy even when you're sitting still. Building a bit of strength makes everything else — running, climbing, carrying — feel easier.
Source: WHO: muscle-strengthening activity 3 days per week for children
Boredom, sadness and stress can feel almost exactly like hunger. It's your brain looking for comfort, not your stomach looking for fuel.
Source: NHS mental wellbeing / emotional eating guidance
Cake isn't evil and broccoli isn't magic. It's how often and how much that shapes your health. Banning a food usually makes you want it more.
Source: British Nutrition Foundation, healthy eating for children
Between 9 and 14 most kids grow taller fast. Sometimes your weight arrives before your height does — and then you stretch out.
Source: NHS child growth and puberty guidance
Fibre from beans, oats, fruit and wholemeal bread takes longer to digest, so your tummy stays satisfied for hours instead of minutes.
Source: NHS: fibre in your diet
Your body can't tell the difference between a 'workout' and 20 minutes of dancing, scootering or a water fight. It all builds your heart.
Source: WHO physical activity guidelines for children and adolescents
Kids who speak kindly to themselves stick with new habits far longer than kids who tell themselves off after a slip.
Source: Research on self-compassion and habit persistence in young people
Eating in the morning helps you concentrate at school and makes big afternoon snack cravings less likely.
Source: NHS healthy breakfast guidance for children
Eating while watching a screen makes people eat more without noticing, because the brain isn't tracking the food.
Source: Studies on distracted eating and portion awareness
After only 4-6 weeks of regular activity your heart pumps more blood per beat, so stairs and running feel noticeably easier.
Source: Exercise physiology: cardiovascular adaptation in youth
People are much more likely to keep a habit when someone else knows about it or does it with them.
Source: Behavioural science: accountability and habit formation
17 more facts are waiting. Finish challenge chapters and quiz stages to open them.
Food before, food after
Trainee level
Muscles grow while you rest
Trainee level
Moving changes your mood chemistry
Trainee level
Your bone bank closes in your twenties
Athlete level
You are carrying trillions of helpers
Athlete level
A fit heart does less work
Athlete level
Growth spurts are not fair, and that's normal
Hero level
Apps and habits use the same chemical
Hero level
The boring middle is where it works
Hero level
Iron carries oxygen to your brain
Hero level
Omega-3s are brain builders
Hero level
Your posture is a habit, not a shape
Hero level
Sunlight is your vitamin D factory
Hero level
Your body clock runs late in teens
Hero level
Ultra-processed snacks are designed to be hard to stop
Hero level
Thirst is a late signal when you're active
Hero level
Gratitude trains your attention
Hero level
Every quiz question is explained here first. Read the stage, then go and get your perfect 10/10.
Your brain is around 73% water, which is why you feel foggy and grumpy before you even feel thirsty.
Source: U.S. Geological Survey — The Water in You
60 minutes a day — and it counts in chunks. Walking to school, dancing in your room and messing about at break all add up.
Source: WHO physical activity guidelines for children and adolescents
9-12 hours. Your body releases most of its growth hormone while you're asleep, so sleep is literally when you get bigger and stronger.
Source: American Academy of Sleep Medicine (AASM) consensus statement
You build around 90% of your bone strength before you're 20. Jumping, running and skipping all tell your bones to get denser.
Source: NHS / National Osteoporosis Society bone health guidance
Around 13 teaspoons — and because it's liquid, it doesn't make you feel full, so your body still asks for food.
Source: NHS sugar guidance
Your brain burns about 20% of your daily energy. After 10 hours asleep the tank is low, which is why concentration dips without breakfast.
Source: British Nutrition Foundation
The colour in fruit and veg comes from different plant chemicals — orange for beta-carotene, red for lycopene, purple for anthocyanins. More colours = more kinds of protection.
Source: NHS Eatwell Guide / WHO fruit and vegetable guidance
Bright light tells your brain it's still daytime, so melatonin turns up late and you lie awake. Dimming screens an hour before bed genuinely helps.
Source: Sleep Foundation / NHS sleep advice
Exercise bumps up endorphins and serotonin. It's one of the fastest, cheapest mood-lifters that exists — and it works even on a bad day.
Source: NHS mental wellbeing / Mind exercise and mood
Long, slow out-breaths activate the parasympathetic ('rest') system through the vagus nerve, which slows your heart rate within about a minute.
Source: Published research on paced breathing and vagal tone
Training creates tiny amounts of damage; your body repairs it stronger while you rest and sleep. Rest days aren't lazy — they're part of the training.
Source: American College of Sports Medicine
A trained heart pumps more blood per beat, so it can beat fewer times per minute. Athletes often rest around 40-60 bpm.
Source: British Heart Foundation
You carry trillions of gut microbes. They feed on fibre from beans, oats and veg, and in return help your immune system and even your mood.
Source: NHS gut health / published microbiome research
Just 2% dehydration measurably reduces concentration and physical performance — so the water bottle is genuine kit, not a nice extra.
Source: European Food Safety Authority hydration review
The talk test: moderate means you can hold a conversation but not belt out a song. Vigorous means you can only get a few words out.
Source: NHS physical activity guidelines
During deep sleep your brain replays the day and moves what matters into long-term memory. Revising then sleeping beats staying up late.
Source: Published sleep and memory consolidation research
Doing something kind activates reward areas in your own brain — which is why supporting your mates feels good, not draining.
Source: Published research on prosocial behaviour and wellbeing
At least 3 days a week — and climbing, hopping, press-ups and carrying things all count. No gym required.
Source: WHO guidelines on physical activity for 5-17 year olds
Laid end to end your blood vessels would stretch around 100,000 km, and blood completes a full lap of your body in under a minute.
Source: British Heart Foundation
Babies start with about 300 bones; many fuse as you grow, leaving 206 in an adult. Your skull plates fuse first.
Source: NHS / Royal Osteoporosis Society
Iron is part of haemoglobin, which carries oxygen. Low iron is a common reason kids feel tired — beans, red meat and dark greens all help.
Source: NHS vitamins and minerals guidance
Protein breaks down into amino acids that rebuild muscle, skin and even hair. Eggs, beans, fish, yoghurt and lentils all count.
Source: British Nutrition Foundation
Lung size barely changes, but your heart, blood and muscles get much better at using the oxygen — so the same run feels easier.
Source: American College of Sports Medicine
Shifting bedtime by hours at weekends is like flying through time zones — 'social jetlag' leaves you groggy on Monday.
Source: Sleep Foundation / published circadian research
Cortisol helps you react to pressure, but it's meant to drop again. Movement, sleep and talking things out all help bring it down.
Source: NHS mental wellbeing guidance
The gut-brain axis is real — that 'butterflies' feeling is your nervous system. Fibre-rich food supports the microbes involved.
Source: Published gut-brain axis research
You replace your outer skin roughly every 28 days — much of household dust is old skin cells.
Source: Published dermatology research
Warming up raises muscle temperature and blood flow, which improves how far a muscle can stretch before it strains.
Source: NHS exercise safety guidance
Vitamin D helps you absorb calcium for bones. In the UK, guidance suggests a supplement in autumn and winter because sunlight is too weak.
Source: NHS vitamin D guidance
Around three quarters of salt comes from packaged food like bread, sauces and snacks — not from what you sprinkle on.
Source: NHS salt guidance / Action on Salt
Every sugary sip starts an acid attack lasting around 20 minutes. Sipping all day means teeth never get a break to remineralise.
Source: NHS oral health guidance
Balance is a brain skill as much as a muscle one — your inner ear, eyes and ankle sensors constantly send updates.
Source: Published motor-control research
The biggest pulses of growth hormone happen in deep sleep early in the night — one more reason late nights cost you.
Source: Published endocrinology research
Social connection is one of the strongest predictors of long-term wellbeing — as important as many physical health habits.
Source: Published longitudinal wellbeing research
Fibre slows digestion so glucose trickles into your blood instead of spiking and crashing — steadier energy through lessons.
Source: British Nutrition Foundation
Sweat cools you when it evaporates. It's a sign your cooling system works — not a measure of how hard you worked.
Source: Published thermoregulation research
Tilting your head forward multiplies the load on your neck. Screen at eye level plus regular movement breaks is the fix.
Source: NHS musculoskeletal guidance
Habits form through repetition linked to a cue — 'after I brush my teeth, I stretch' beats a vague plan to do it sometime.
Source: Published habit-formation research
Training builds more capillaries and mitochondria — tiny power stations in your cells — so you make energy more efficiently.
Source: American College of Sports Medicine
Caffeine's half-life is about 5-6 hours, so an afternoon energy drink can still be blocking sleep signals at bedtime.
Source: Published caffeine pharmacology research
Your brain's internal map of limb length lags behind fast growth, so coordination temporarily dips. It catches up.
Source: Published adolescent development research
Tinned fish with soft bones, tofu, fortified plant milks and leafy greens all deliver calcium for the bone bank you build now.
Source: NHS calcium guidance
A longer exhale boosts vagal activity and slows heart rate. Try in for 4, out for 6, for one minute.
Source: Published paced-breathing research
Bright morning light anchors your circadian rhythm, which schedules melatonin about 14-16 hours later.
Source: Published circadian rhythm research
Adaptation happens during recovery. Skipping rest raises injury risk and flattens progress — rest is part of training.
Source: American College of Sports Medicine
Studies show people eat noticeably more when food is soft, energy-dense and quick to chew — your fullness signals arrive late.
Source: Published ultra-processed food trials (NIH)
Research consistently links appearance-based social comparison with worse mood. Comparing to your own last week works better.
Source: Published adolescent social media research
Short sleep is linked with catching more colds. Sleep, varied food and movement beat any single 'immune booster' product.
Source: Published sleep and immunity research
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