Guest post by Senior lecturer and researcher, Charlotte Gowers.
Picture a 15-year-old basketball player. She trains twice a week with her club, has a school fixture on Wednesday, drives to a regional squad session on Sunday, and does PE on top of all of it. She has always been the most dedicated and capable player on the team.
Lately, though, something is off. She picks up every cold going round. She has had two “niggles”. Her legs are heavy and her shot keeps falling short, despite training more than ever. She is flat, snappy, and sleeping badly. Her periods, which started two years ago, have become irregular or stopped altogether.
Her parents put it down to hormones, GCSEs, a growth spurt, bad luck with injuries. Her coach says she needs to work harder.
There is a reasonable chance she simply isn’t eating enough for the amount she is doing.
A syndrome, not a slip-up
The condition is called Relative Energy Deficiency in Sport, or REDs. It was named by an International Olympic Committee expert panel in 2014, updated in 2018, and updated again in a 2023 consensus statement that remains the reference point for clinicians today.
The underlying idea is simple. Your body needs energy to train and it also needs energy to run everything else: bones, hormones, immune system, brain, and, in a teenager, growth and puberty. When exercise takes too large a share of what has come in, there isn’t enough left for the rest. Sports scientists call the shortfall low energy availability. Sustained over weeks and months, it produces the cluster of health and performance problems known as REDs.
The 2023 statement describes effects across many body systems: bone health, hormonal and menstrual function, immunity, metabolism, cardiovascular health and mental health among them and also stresses that any athlete can be affected regardless of sex, sport or level. It also flags something parents of team-sport children should note: REDs looks very much like overtraining, and the two are easy to confuse.
It isn’t only a problem for runners and gymnasts
Ask most people which young athletes are at risk and they will name distance runners, gymnasts, dancers, jockeys, and athletes in weight-category sports such as judo or lightweight rowing. Those sports do carry known risk, and awareness there has improved.
Team sports are the blind spot, for a structural reason: nobody is adding up the load.
A committed 14-year-old basketball player, footballer, netballer or swimmer can easily be attached to three or four different teams: school, club, region or county, an academy, plus a strength and conditioning session someone has told them to do. Each coach sees their own slice. The school coach doesn’t know about Sunday. The club coach doesn’t know about Wednesday’s fixture. Nobody sees the week as a whole.
Except you. Parents are often the only people with the full picture, and frequently the only ones in a position to notice that the picture has quietly become unsustainable.
Why adolescence raises the stakes
Two things make the teenage years the worst possible time for a prolonged energy shortfall.
The first is growth. A child in a growth spurt has substantial energy demands before they have touched a ball. Sport sits on top of that, not instead of it. Requirements can rise sharply over a matter of months, and eating habits often don’t move with them.
The second is bone. Adolescence is when the skeleton is laid down; the great majority of adult bone mass is banked by the late teens and early twenties. Bone built then has to last a lifetime. Energy shortfall during those years and particularly when combined with disrupted hormones can compromise that process, and the window does not reopen later. This is why repeated bone stress injuries in a young athlete deserve a proper look rather than a fortnight of rest and a shrug.
This is for boys just as much as girls
Boys are not exempt, and the syndrome was renamed precisely because the older “female athlete triad” framing left them out. The difficulty is that boys have no equivalent of a missed period unless you want a VERY awkward conversation with your teenage son so under-fuelling in male athletes tends to be caught later and after more damage has been done. What it looks like instead is a boy whose growth or puberty seems to have stalled next to his mates, who is always the one carrying a knock or a cold, who is putting in more gym work than ever and getting no stronger, and who has become flat, irritable and hard to rouse. The driver in boys’ team sport is also often different: rather than eating less, they are simply doing far more while the pressure to “get bigger” leads them to focus on protein and supplements at the expense of eating enough overall.
Usually, nobody chose this
It is tempting to assume an under-fuelled teenager must be dieting. Often they aren’t.
Hard training blunts appetite, sometimes for hours. A 6pm session followed by a 9pm arrival home is not conducive to a decent meal. A child who leaves at 7.30am and doesn’t get home until after 8pm has a genuinely tight window in which to eat. Add fussiness, a fashionable decision to cut out a food group, or an eight-hour gap between lunch and a late training session, and the shortfall builds without any intention behind it.
That said, intentional restriction is a real driver too. Disordered eating, body-image pressure, comparison on social media, and offhand remarks from coaches or teammates about being “leaner” or “carrying a bit” all feature.
Signs worth taking seriously
Individually these are unremarkable. Clustered, and persisting for more than a few weeks, they warrant a conversation:
• Frequent illness — always the one with a cold or a sore throat
• Injuries that keep coming, especially bone stress injuries, or niggles that take unusually long to settle
• Performance plateauing or declining despite training more
• Fatigue out of proportion to the load, and poor sleep
• Periods that are late, irregular, or have stopped — in a young athlete this is a signal, not an inconvenient side effect to be tolerated
• Mood changes — irritability, low mood, anxiety, withdrawing from friends
• Growth or development that seems to have stalledrelative to peers
• Rigid rules around eating — skipping meals, cutting out whole food groups, anxiety about eating with others, “clean eating” that keeps narrowing
• Guilt about rest — training on top of training, distress at a day off, exercising while injured
What parents can actually do
Add up the week. Write down every session across every setting. Parents are regularly surprised. If the total looks like a lot, it probably is and you may be the only person able to say so to the various coaches involved.
Close the gaps. The practical fix is usually not a diet plan but timing: something substantial before training, something soon after, and no eight-hour holes in the day. A packed extra meal for the car home is unglamorous and effective.
Keep carbohydrate on the plate. Inadequate carbohydrate intake was singled out as an emerging concern in the 2023 statement. Bread, pasta, rice, potatoes and cereal are not the enemy of a growing athlete.
Watch the language at home. Comments about bodies, “good” and “bad” foods, or earning dinner through exercise land differently in a teenager already immersed in sporting body talk.
Protect rest and off-season. Recovery is when adaptation happens. A child who never has a break isn’t more committed; they’re more likely to be injured.
Go to the GP early. Say the words “I’m concerned about relative energy deficiency in sport.” Ask about bone health, hormones and blood tests where appropriate, and ask for referral to sports medicine or a registered dietitian with sports experience if the picture warrants it. Don’t wait for a stress fracture to make the case for you.