Junior tennis nutrition: the problem is almost never what they are eating
Written for parents and coaches. It contains no restriction advice and no diet plans for children, and that is deliberate.
Research on youth tennis players keeps returning the same finding, and it is not the one parents expect. Fleming and colleagues followed 27 players across the under-12, under-14 and under-16 groups for a week of training and competition. Group mean intakes came out between 1,965 and 2,232 kcal a day, with no meaningful difference between age groups and none between training days and competition days, in a population whose requirements can run anywhere from 2,000 to 5,000 depending on size, training load and where they are in growth.
What they eat is usually fine. How much they eat is the problem: not enough of anything.
One study of adolescent competitive players found that only 29 percent reported a carbohydrate-dominant meal the day before match play. Another found no increase in carbohydrate intake on competition days at all, and no increase at dinner as a recovery strategy after matches. The pattern is an absence of any deliberate choice, in a sport that asks a great deal of children, rather than poor choices.
Why the junior format makes it worse
Professional players usually play one match a day. Juniors frequently do not.
The systematic review of junior tennis demands puts it plainly: junior players usually take part in multiple matches a day and may enter several draws, singles and doubles, sometimes across more than one age group in the same event. Add a training load that is already high and a venue where the food options are a vending machine and a burger stand, and the day is designed to produce a deficit.
Then the child goes to school on Monday. And grows.
Growth, training and school all draw on the same energy. Growth is the one that cannot be postponed, and if the budget will not stretch, it is the one the body protects by taking from somewhere else.
What under-fuelling actually costs
The word deficit sounds administrative. The consequences are not.
Sustained low energy availability in a growing athlete is associated with stalled growth, delayed or disrupted puberty, reduced bone mineral accrual and a higher injury rate, particularly bone stress injuries in the feet and lower legs, which happen to be exactly where tennis loads a young skeleton.
Bone is the part parents underestimate. The adolescent years are when most of the adult skeleton is laid down, and it is a window that does not reopen. A season of under-fuelling at 14 is not repaid by eating well at 22.
Researchers commonly point to an energy availability of around 45 kcal per kilogram of fat-free mass per day as the level associated with normal physiological function. The figure comes from adult data and is applied to adolescents as a practical reference, with the caveat that a growing athlete may need to sit at or above it rather than near it. It is context for the adult doing the shopping, and it should never be handed to a 14-year-old as a target; I would not put it in front of one.
The signs, before the results move
Performance drops last. The earlier signals are duller and easier to explain away.
A player who is training normally and getting slower. Frequent minor illness. Injuries that arrive without an incident behind them. A growth curve that flattens while their friends keep going. In girls, a menstrual cycle that becomes irregular or does not arrive, which is a signal and not an inconvenience, and which needs a doctor rather than a forum.
And the one that most parents recognise instantly once it is named: a child who comes home from training and empties the fridge. That is usually not greed. It is a body collecting on a debt run up between breakfast and 6 pm.
What to do about the tournament day
The tournament day is where the deficit is built, because it is long, unpredictable and badly catered.
Pack more than you think is reasonable, in things that survive a bag. Assume the day will run late, because junior draws almost always do, and assume that whatever is on sale at the venue will be the wrong food at the wrong time.
Feed between matches rather than after them. The gap between a singles and a doubles match is the single most valuable window of the day and it is the one most commonly spent sitting on a bag looking at a phone. Carbohydrate goes in first and quickly, because the next match may be sooner than anyone said.
Do not introduce anything new on a tournament day. This is a rule for adults too and juniors break it more often, usually because a parent has read something the night before.
Get dinner right on the night after, not just the night before. The research finding that juniors do not raise carbohydrate at dinner after competition is, to me, the most actionable line in the whole literature. Tomorrow's match is fuelled tonight.
Hydration, which is different in children
Younger players differ from adults on this: they carry a higher surface area relative to body mass, they sweat less efficiently, and their thirst response is a less reliable guide than an adult's.
The practical consequence is that hydration in juniors has to be prompted rather than assumed. A bottle in the bag is not a plan. A refill schedule through a tournament day is, and it is not babying anybody.
The nutrients that matter in this window
Three come up repeatedly in adolescent athletes and all three are ordinary food problems rather than supplement problems.
Iron. Requirements rise sharply through adolescence, to around 11 mg a day for boys and 15 mg for girls aged 14 to 18. Deficiency shows up as unexplained fatigue and slowed recovery long before anything else, and it is more common in girls. It is also a thing to test rather than guess at, and to treat on medical advice rather than by buying a supplement.
Calcium. Around 1,300 mg a day between 9 and 18, which is the highest requirement of any point in life, arriving in exactly the years when dairy often drops out of the diet.
Vitamin D. At least 600 IU a day, and worth attention in players who train indoors or live somewhere with a real winter.
The conversation I want to be careful about
Somewhere between 12 and 16, most junior players get heavier, and some of them get slower for a while. This is normal, it is a growth spurt doing what growth spurts do, and coordination usually catches up within months.
It is also the moment at which somebody suggests the player should lean up.
Do not. I say this as someone whose professional life is planning weight reduction, and I say it because I plan weight reduction for adults who have finished growing. A 14-year-old in a growth phase who eats less does not become a faster tennis player. She becomes a smaller one, with worse bone, later puberty and a higher chance of a stress fracture, and the tennis problem she was trying to solve is not touched.
If body composition genuinely needs attention in a young player, it is a medical conversation with a doctor and a dietitian who work with adolescents, held privately, without a number said out loud in front of the child. It is not a coaching conversation and it is certainly not a car-journey conversation.
All of this, with the week set out day by day and a table of what to say instead of the things that get said, is in Junior Tennis: A Parent's Guide.
What I would tell a parent
Your job in this is logistics rather than nutrition science. Breakfast happens. Lunch happens even on a school day with a match after it. The bag has more food in it than seems sensible. Dinner after a tournament day is the biggest meal of the week, not the smallest.
Watch the growth curve rather than the scale, and watch it over months rather than weeks.
And if something looks wrong, take it to a doctor early. Under-fuelling in a growing athlete is one of the few problems in this sport that gets straightforwardly worse the longer it is left, and one of the easiest to fix if it is caught in the same season it started.
Common questions
More than most of them do. A study of 27 youth tennis players across the under-12, under-14 and under-16 groups found group mean intakes between 1,965 and 2,232 kcal a day, with no increase on competition days, while requirements for adolescent athletes commonly fall somewhere between 2,000 and 5,000 kcal a day depending on body size, training load and stage of growth. The practical answer is that a junior player needs 3 meals and snacks around them every day, not only on competition days, and that the amount is set by their size and their week rather than by a figure from an article.
Training normally but getting slower, frequent minor illness, injuries with no incident behind them, a growth curve that flattens, and coming home to empty the fridge. In girls, a menstrual cycle that becomes irregular or does not arrive is a signal that needs a doctor. Performance decline is usually the last sign to appear rather than the first.
Feed between matches rather than after them, with carbohydrate going in first and quickly, because the next match may start sooner than the schedule suggests. Pack more food than seems reasonable in forms that survive a bag, assume the day will run late, and introduce nothing new on a competition day. The gap between a singles and a doubles match is the most valuable window of the day.
No. Getting heavier and briefly slower between roughly 12 and 16 is normal growth, and coordination usually catches up within months. Restricting food in a growing athlete risks stalled growth, delayed puberty, reduced bone mineral accrual and stress fractures, and does not solve the movement problem. If body composition genuinely needs attention, that is a private medical conversation involving a doctor and a dietitian experienced with adolescents.
The nutrients that come up repeatedly in adolescent athletes are iron, calcium and vitamin D, and all three are ordinarily food problems rather than supplement problems. Iron requirements rise to around 11 mg a day for boys and 15 mg for girls aged 14 to 18, calcium sits at around 1,300 mg a day between 9 and 18, and vitamin D at least 600 IU. Iron in particular should be tested and treated on medical advice rather than supplemented on suspicion.
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Educational material, not medical advice. Concerns about growth, energy intake or menstrual function in a young athlete should be taken to a doctor. Nutrient reference figures are general population values for the age bands stated.