By Jill Castle, Registered Dietitian and Child Nutrition Expert

Can a growing swimmer be too thin?

In today’s world, there is much ado about weight—too much weight. But a growing child who is too thin may be just as troublesome.

Most of the time, children are moving through the natural ups and downs of growth, and there’s no cause for worry. But the growing swimmer has a delicate balance to strike—matching energy needs for growth while covering the nutritional demands of the sport.

Unmatched energy needs may stem from the rigors of regular training, high energy demands associated with growth spurts, poor eating, and/or a poor diet. If young swimmers are too thin and missing out on calories and nutrients, their performance in the water, their growth and overall health may suffer.

What’s Normal, What’s Not?

Both growth and swimming are calorie-hungry. Normal growth relies on eating enough food (and of good quality) to cover the energy and nutrient demands of swimming and growth.

For the school-age swimmer, normal eating is three meals and 2-3 snacks per day. Teens, particularly males, require more energy for the adolescent growth spurt, and may need 3-4 meals and 1-2 snacks per day.

Conversely, skipping meals or snacks, dieting for weight or fat loss, pushing nutrients for performance or body composition benefits, and losing or failing to gain weight is not normal.

Feeding the thin swimmer requires attention to food types, quantity and timing of eating. The goal is not to “fatten up” the swimmer, but to match his energy needs for growth and swimming, allowing his natural, healthy body to take shape.

Six tips for helping the thin swimmer boost nutrition:

Square Up Meals: Make sure to include a variety of food groups, aiming for at least 4-5 at main meals (protein, whole grains, dairy, fruit, vegetables and healthy fats). Scale back on dining out, especially fast food establishments.

Size Up Snacks: Offer 2-3 food groups, focusing on taste and nutrition. Cereal, fruit and milk, or nut butter, crackers and raisins are examples of a hearty, nutritious snack.

Drink with an Advantage: Water is great for everyone, but the thin swimmer should focus on drinks that offer calories and nutrition. Drinking milk or non-dairy substitutes, 100% juices, smoothies and breakfast drinks can be an easy way to down some extra calories and nutrients.

Pre-Bedtime Snacking: Eating something prior to bedtime can help the thin swimmer supply the body with extra calories that won’t be burned off. Try peanut butter toast, instant pudding made with whole milk, or a milkshake.

Fat Padding: The addition of fat can boost calories, and ease the pressure and requirement for eating large quantities of food. Adding margarine, mayonnaise or avocado to sandwiches, “double-dressing” cooked pasta (toss in olive oil, then top with butter or olive-oil soft spread) or sprinkling cheese on entrees are just some examples of adding extra calories to food.

Time It: Staying on a structured approach with eating helps assure nutrition is on board, while helping build a rhythmic appetite for eating. School-age swimmers can eat every 3-4 hours, while teens can schedule meals and snacks every 3-5 hours.

Jill Castle, MS, RD is a registered dietitian and child nutrition expert. She is the co-author of the upcoming book, Fearless Feeding: How to Raise Healthy Eaters from High Chair to High School (2013), and creator of Just The Right Byte, a child and family nutrition blog. She lives with her husband and four children (one swimmer!) in New Canaan, CT.