Energy Requirements
The energy balance in a healthy individual is defined as the difference between the
energy intake and the energy expenditure. If the balance is positive the excess will
accumulate mainly as body fat. If, on the other hand, the balance is negative, it
will lead to a decrease in body compartments.[5 ] Different studies analyzing the loss of fat in relation to the intensity of the
physical performance[6 ]
[7 ] observed that adiposity is only modified in high-performance PA, but it is not noticeable
in situations of moderate intensity. Nevertheless, there are contradictory studies
regarding fat distribution: while some authors have described an inverse relationship
between fat at a central level and intense PA,[8 ] and others, such as the AVENA study (Spanish acronym for Food and Assessment of
the Nutritional Status of Adolescents), found no relation.[9 ]
The nutritional status of children is very vulnerable due to the high demand of nutrients
related to the negative balance storage of body components. Excessive or insufficient
changes in energy balance in children and adolescents can not only modify body composition,
but also affect maturation and functional and structural tissue development.[10 ]
Energy requirements in children and adolescents are determined, in addition, by the
energy needed to grow, which depends on the energy destined to synthesize fats and
proteins that form tissues since the content of carbohydrates (CH) of tissues is habitually
insignificant.[11 ]
The recommendations for different intensity levels of PA must be accompanied by a
good nutrition and vice versa. PA may account for around 25 to 30% of the total daily
energy expenditure in a non-athletic individual and varies according to the level
of PA.[12 ] Moreover, this expenditure decreases because of growth and increases at the expense
of PA from the first year onward, though subject to individual variability.[13 ] Other factors such as the social environment of older children and adolescents have
also been studied. Thus, rural societies reflect a greater energy expenditure and
nutritional requirements in comparison with industrialized cities or countries. A
reason for this could be that children who belong to rural or traditional societies
start working at a very early age, either at home or outside it, whereas children
in industrialized cities continue studying until a later age, thus consuming less
energy.[11 ]
Therefore, there is a big difference in energy requirements between sedentary children
and those whose level of exercise intensity is high for their age. This difference
can be up to 15 times greater.[5 ]
The maximum oxygen uptake (VO2 max) objectively calculates the energy loss. This parameter must be measured individually
for each activity. However, its implementation is not very extended since it is somewhat
costly. VO2 increases in aerobic exercises until it reaches a stable rhythm, which happens before
in children aged10 to 11 years than in adults[5 ] and depends on the activity level.[12 ] In this way, the calorie expense in different sports can be assessed and it is going
to depend on the body weigh. Palavecino[12 ] found a big change between several sports after studied calories burned in 10 minutes
of different sports practice, such as 34 cal for a person with 20 kg against 110 cal
of a person with 65 kg, both after practicing volleyball.
Nutrition Requirements
Even though each nutrient has a particular effect on the sports performance, the nutritional
requirements that child athletes present are generally influenced by the energy balance.
On the other hand, the nutrition requirements are calculated for individuals with
a normal body mass index (BMI) and can, therefore, vary in individuals with low weight,
overweight, obesity, or a greater muscle development. To assess the average requirements
in childhood and adolescence, three age groups must be considered: preschool children:
(under 3 years old), schoolchildren (aged 3–10), and adolescents (aged 10–18). For
each of these groups, the energy used for growth and the level of PA are considered
(physical activity level [PAL]: 1.40, 1.58, and 1.75, respectively). These values,
associated to basal metabolism (for each age group, gender, size, and weight), are
used to estimate the average requirements for each age group. Nevertheless, an individual
can vary the PAL associated with their age group. In this case, the energy requirement
will increase for children who perform 30 minutes of moderate PA for 5 or more days
a week, 60 minutes of active sport five times a week or intense aerobic exercise associated
to a competition sport in 0.15, 0.3, or 0.6 PAL units, respectively.[14 ]
In addition, an inverse relation between PAL and percentage of body mass in young
children and adolescents[15 ] has been documented, especially in males.[16 ] Thus, children with intense accumulated performance of 2 hours have shown a greater
reduction in body fat levels than those with lower performance.[17 ] A summary of macro and micronutrients and in which foods these are present are shown
in [Table 1 ].
Table 1
Macro and micronutrient content of several foods
Nutrient
Food
Fast absorption carbohydrates
Fruits, jelly, milk, and cake.
Slow absorption carbohydrates
Cereal and its products (flour, pasta, rice, bread, corn, and oats), legumes (chickpea,
bean, and lentil), and potatoes
Fats
Olive oil or other vegetable oil (less palm oil or coconut oil), oily fish, and nuts
Proteins
Fish, meats, milk, egg, and soya bean
Vitamin A (retinol)
Orange and green vegetables, liver, and milk
Vitamin B1 (thiamine)
Lean meat, liver, and whole wheat
Vitamin B2 (riboflavin)
Milk and its products, legumes, cereals, meats, and vegetable
Vitamin B3 (niacin)
Legumes, whole wheat, fish, and liver
Vitamin B5 (pantothenic acid)
Egg, milk and its products, legumes.
Vitamin B6 (pyridoxine)
Fish, lean meat, and whole wheat
Vitamin B8 (biotin)
Legumes, fresh vegetables, nuts, dried fruits, meat, liver, and yolk
Vitamin B9 (folic acid)
Legumes, whole wheat, green leafy vegetables, nuts, orange, banana, and dried fruits
Vitamin B12 (cyanocobalamin)
Meat, fish, and yolk
Vitamin C (ascorbic acid)
Strawberry, citric fruit, kiwi, tomatoes, pepper, and green leafy vegetables
Vitamin D (calciferol)
Oily fish, liver, and milk
Vitamin E (tocopherol)
Nuts, vegetables oil, and green leafy vegetables
Vitamin K (phylloquinine)
Green leafy vegetables, liver, and yolk
Calcium
Milk and its products and dried legumes
Phosphorus
Milk and its products, fish, meat, dried fruits, and whole wheat
Potassium
Fruits, vegetables, milk, fish, and meat
Sodium
Salt, salted food, milk, and cheese
Magnesium
Whole wheat, nuts, and green leafy vegetables
Iron
Meat, fish, seafood, meat, egg, legumes, and whole wheat
Zinc
Meat fish, whole wheat, and seafood
Fluorine
Tea and seafood
Selenium
Fish, whole wheat, and meat
Copper
Fish and meat
Iodine
Fish, seafood, and algae
Chrome
Fat, vegetable oils, and meat
Carbohydrates
Especially during exercise, carbohydrates (CH) are used as priority fuel, and fat
burning takes a second place. The needs for CH have been related to the child's physical
form, the type of training, the intensity, and duration of the exercise or nutritional
status.[18 ]
In general, the use of CH increases with intensity and decreases with duration. Stored
muscle glycogen and blood glucose are thus the main sources of energy through anaerobic
glycolysis. As intensity decreases and duration increases, lipids become the main
source of fuel through the aerobic system. Nonetheless, glucose is still of great
importance, especially at the beginning of the activity and in the stages when oxygen
supply does not meet the demands of the aerobic metabolism, such as endurance runs,
which require an additional effort upon reaching the goal.[10 ]
One of the negative effects of extended exercise is hypoglycemia. It originates mainly
at brain level and is independent of the energy substrates reserve available in the
form of free fatty acids. The energy needs of the brain are satisfied almost exclusively
through glucose. Its deficit manifests itself as fatigue, general malaise, inability
to concentrate, lack of coordination, and even collapse. A good training helps athletes
gradually acquire greater resistance to fatigue, which leads to achieving lower sensibility
to hypoglycemia and the adaptation of the nervous system to this situation. Thus,
energy is obtained in a sustainable way from blood lactate. The synthesis of lactate
starts before reaching VO2max . However, children have a lower ability to obtain energy from lactate, which leads
to a lower accumulation of lactate and consequently less fatigue. Therefore, they
can work out for a longer period but at a lower intensity.[5 ]
It is necessary for children to have suitable glycogen reserves to face prolonged
exercise, especially when the duration of the PA exceeds75 minutes. The appearance
of exhaustion will depend on CH richness of the diet. It has been observed that a
diet rich in CH is critical to maintain the performance in both training and competition,[19 ]
[20 ] although this issue has not been described in detail for adolescents and children.
This has led to the so-called supra-compensation, according to which the athlete can
reach the maximum levels of muscle glycogen, thus increasing the time of exercise
until reaching exhaustion.[21 ] For example, drinking a beverage containing 6% of glucose can provide the proper
amount of CH, improving the performance of cyclists.[22 ]
In this way, the necessary CH (dietary reference intakes [DRIs]) in a child with normal
PA will be approximately 50 to 55%, which corresponds to 6 to 10 g/kg.[23 ] It must be ensured that at least half of the calorie intake of children who practice
high-performance sports comes from CH, and it should be spaced during the day. In
the case of very intense exercise, the total intake must increase up to 70%.
The suitable intake of CH is especially relevant in the competition day, when it is
necessary to reinforce the deposits of muscle glycogen in the previous hours and during
exercise to ensure a correct performance during the whole duration of the activity,
especially if it lasts longer than an hour. Once the activity concludes, the athlete
must have a meal which avoids post-exercise muscle catabolysis. Thus, the athlete
will need 4 g/kg of CH in the 3 to 4 hours before the sports activity, 0.5 to 1 g/kg
the previous hour, 0.7 g/kg every hour distributed every 15 to 20 minutes during the
activity, and 1 to 1.5 g/kg after it.[24 ]
Fats
As previously mentioned, fats are the suitable fuel for low-intensity and long-duration
activities. Physical exercise can lead to an increase in the use of fats and their
mobilization. On the one hand, the oxidation of lipids in the form of free-fatty acids
increases within the muscle cell mitochondria reducing their concentration inside
the cell which in turn stimulates the flow of free-fatty acids into the blood. This
fact is due to the increase in adrenaline and noradrenaline during exercise that stimulates
lipolysis. Other mechanisms are the decrease in circulating insulin and the increase
in the activity of the central nervous system. Due to their complexity, these processes
are very slow. About 20 to 30 minutes after starting the exercise, the function of
the free-fatty acids begins to be activated, and they become available for a long
period. It has not been proved that additional supplements of fatty products could
improve performance in sport activities, since the body fat deposits are enough to
balance out the needs.[10 ]
A beneficial effect of poly-unsaturated fatty acids (PUFAs) has also been suggested
(especially omega-3) due to the increase in the synthesis of eicosanoids and anti-inflammatory
cytokines. The British Nutrition Foundation recommends a total daily intake of 3 to
5.5 g PUFAs, considering that a higher intake will not influence performance or inflammation
and immunity. On the other hand, an excessive and imbalanced intake of PUFAs might
compromise the athlete's health due to the oxidative stress produced, which can exceed
the antioxidant mechanisms.[25 ] To prevent this situation, the intake of oil rich in oleic acid (extra virgin olive
oil) is recommended as the main source of fat, since it protects the membranes from
lipid peroxidation providing antioxidants and keeping a correct ratio of omega-6/omega-3
(in general, 4:1).[26 ]
Carnitine is another supplement which is currently used to improve sports performance.
Its use is based upon the fact that it optimizes the metabolism and use of fats. However,
it has not been proved whether its regular intake improves performance during high-intensity
anaerobic exercise or whether it influences the accumulation of lactic in this type
of exercise. It is important to point out that, although L-carnitine is a safe supplement,
D-carnitine can have toxic effects.[27 ]
Thus, the DRI of fats both in sedentary children and children who do high-performance
exercise are similar. In general, 25 to 35% of calorie intake in children aged 1 to
18 should come from fats. Less than 10% of fatty acids consumed must be saturated
and up to 10% must be polyunsaturated, and from these, 1 to 2% must come from linoleic
acids. Moreover, 10 to 15% must be monounsaturated, with a maximum input of daily
cholesterol of 300 mg.[28 ]
Proteins
Energy from amino acids can be supplied through the diet or by the endogenous degradation
of proteins in muscles. Given that the organism uses the diet CH before prolonged
exercise, the main source of amino acids used afterward comes from the degradation
of muscle proteins. Around 10 to 15% of the energy can be provided in this way.
Currently, the effects of the intensity and duration of exercise on the synthesis
and degradation of proteins are uncertain. Exercise leads to a decrease in protein
biosynthesis in muscle and liver, linked to an increase in its degradation.[10 ]
Only some foods contain proteins of high biological value with the presence of essential
amino acids. These foods are proteins of animal origin, especially eggs and, to a
lesser extent, beef and chicken, fish, and cow milk. Moreover, they present a greater
digestibility than those derived from plant origin which, despite lacking some amino
acids, are rich in methionine and lysine. If deficit of some of essential amino acids
occurs, there is a degradation of other proteins to compensate which can decrease
the strength and resistance of the individual to exercise.
In consequence, protein intake is essential for growth and intense exercise or high-stress
situations. Proteins are responsible for muscle synthesis and repair and must provide
10 to 15% of the calories in a diet. Current recommendations (DRI) are equal for both
sexes: 1.1 g/kg/day for children aged 1 to 3, decreasing to 0.95 g/kg/day until adolescence.
The Recommended Dietary Allowances (RDA) for adolescents aged 16 to 19 should be reduced
to 0.85 g/kg/day.[28 ] In addition, protein intake after sport activity should be 0.2 to 0.4 g/kg.[24 ] An excessive protein intake does not increase muscle mass, but can rather contribute
to increasing the fat compartment, since the amino acid deposit is not modifiable.
In addition, it can increase the risk of health issues resulting from a diet lacking
other nutrients.
However, the intake of proteins related to the intake of CH as useful nutrients in
the recovery process should be considered. They must be consumed within 30 minutes
after exercise and, again, within the next 2 hours to help restore glycogen and allow
muscles to recover.[29 ]
[30 ]
Vitamins
An inadequate diet that do not meets the requirements of macro- and, especially, micronutrients
can lead to a decrease in the performance of the child athlete. Even if the diet is
rich in macronutrients, the input of vitamins and minerals could be incorrect.[31 ] Correcting these dietary errors and supplying the adequate micronutrients would
avoid the use of vitamin supplements which many athletes take and that does not significantly
improve performance during exercise.
Water-soluble vitamins, specifically B vitamins such as B1 , B6 , niacin and folic acid are essential for certain metabolic systems of the organism.
Thus, vitamin B could enhance the Krebs cycle. Vitamin B6 is closely linked to metabolic processes involving amino acids. Niacin plays a fundamental
role in the electron transport chain. Folic acid participates in nucleic acid metabolism.
Indeed, it is currently being debated whether there is a need to provide these vitamins
as supplements. These vitamins can be supplied through the daily intake of fresh fruits
and vegetables or through amino acid supplements[10 ] in the case of certain athletes.
Among lipid-soluble vitamins, vitamin D is the most outstanding. The role of this
vitamin, nowadays considered as a hormone, is essential for the metabolism of the
skeletal system, and suitable levels have been associated to injury prevention, better
neuromuscular function, increase in type II fibers, lower inflammation, and lower
risk of stress fractures. Current recommendations of vitamin D intake are 600 IU/day
for children aged between 4 and 18 years.[32 ] The normal values of vitamin D also vary depending on geographic location and race.
Athletes living in northern latitudes or those who train indoors (for example, figure
skaters, gymnasts, and dancers) have a greater probability of suffering from a lack
of vitamin D.[29 ] This has also been observed in a study conducted with swimmers aged 18 to 30 years.
Swimmers who train outdoors do have a higher mineral density and vitamin D level than
those who train indoors.[33 ] It is therefore essential to ensure a sufficient sunlight exposure. If supplements
are used, these must be recommended by healthcare professionals, who must consider
side effects of toxic levels, such as hypercalcemia and nephrocalcinosis.
Minerals: Iron, Calcium, and Magnesium
Regarding minerals iron, calcium, and magnesium deserve a special mention. Lower serum
iron and decreased ferritin levels have been observed in endurance athletes, which
can lead to anemia in these children.[10 ] This situation involves a reduction in oxygen uptake and in the elimination of carbon
dioxide that implies a decrease in muscle pH and therefore the alteration of metabolic
processes in skeletal muscle. Moreover, a drop in the number of erythrocytes causes
lower blood viscosity and results in a higher cardiac output. Additionally, intense
exercise seems to increase plasma transferrin, which delays the release of iron. For
these reasons, it is recommended to assess the iron levels, especially from adolescence
onward and mainly in girls with abundant bleeding during menstruation to supply iron
if needed.[34 ] This control is also important in any athlete with a poor diet. During childhood
and adolescence, it is mandatory to maintain adequate blood iron levels to ensure
growth and the rise in blood volume and lean muscle mass.[35 ] Children aged between 9 and 13 years must ingest 8 mg/day to avoid depletion in
their iron reserves and iron deficiency anemia. Adolescents aged between 14 and 18
years require a higher amount of iron, up to 11 mg/day for males and 15 mg/day for
females.[36 ]
Calcium requirements in athlete children and adolescents are higher than in sedentary
children during development. On the other hand, excessive PA can cause bone decalcification
affecting growth. Female athletes are more prone to amenorrhea, which leads to loss
of bone mass resulting in increased fracture incidence. A correct intake of calcium
and vitamin D, even in the form of supplements, is recommended to avoid a decrease
in bone mass. Nevertheless, ensuring the intake of dairy products, which can be low
in fat, is the most adequate measure. Calcium deficit can trigger muscle cramps, which
can be avoided by slightly increasing the intake of this mineral (100–150 mg). The
reference daily calcium intake is 1000 mg/day for children aged between 4 and 8 years
and 1300 mg/day for children aged 9 and 11 years.[37 ]
Magnesium intake is important in sports involving weight restrictions, such as ballet
or gymnastics. During and after exercise, there is usually a great loss of this mineral,
especially in anaerobic sports and in prolonged events at high temperatures increasing
through perspiration. It was observed that the magnesium intake was lower than the
recommended daily intake whereas the relation calcium/magnesium was greater in a study
conducted with elite basketball, handball, and volleyball players. Directly proportional
associations were also observed between magnesium intake and performance tests involving
jumps and variables of isokinetic strength (extension and flexing).[38 ]
Nowadays there is an increase in the use of supplements among young. They claim to
enhance health (to avoid deficits, anemia, and osteoporosis) or to improve performance.
Currently, multivitamins associated to the so-called ‘ergogenic aids’ (such as creatinine
or caffeine) are the most consumed.[39 ]
[40 ] Their use is generalized despite the fact that studies have not proven that they
enhance performance.[41 ] Although the use of vitamins and minerals, as previously mentioned, is not necessarily
dangerous; if consumed in excess, some of them may result toxic especially if they
react with other nutrients.[42 ] Besides, some of the commercial preparations associate other molecules, such as
steroids,[40 ] or they contain doses that have not been proven to affect health.[43 ] The nutritional component of the training program of young athletes is especially
important since there are many connections among nutritional deficiencies, growth,
development, sports performance, and injury prevention.[19 ] Nonetheless, research on the qualities of supplements in adolescent athletes aged
under 18[41 ] is very scarce. During the developmental stages, many physiological changes take
in place, it is therefore very difficult to specify the consequences and possible
side effects of a regular intake of vitamin supplements.[39 ] Most studies have proven that athletes tend to have a greater control over the intake
of healthy foods and therefore would not need a greater input of vitamins and minerals
although we must be alert to the risk of associated deficiencies.[19 ]
[31 ]
Hydration
Perspiration during exercise leads to a loss of liquid that not only decreases performance,
but can also affect health directly. Restoring liquids during exercise is therefore
crucial. The goal is to choose the right moment for them to be absorbed as quickly
as possible. The variable which determines liquid absorption to a greater extent is
gastric emptying, which increases as the amount of liquid consumed increases up to
a maximum of 600 mL, when it becomes stable. This variable is the same both for a
person at rest and one who performs moderate exercise, whereas in a person who does
intense exercise the emptying is reduced altering rehydration. Moreover, liquid absorption
also depends on the type of movement performed and the amount of liquid consumed.
The composition of the liquid ingested is another factor to be considered. Active
glucose and sodium transport, passive potassium transport, and neutralization of some
acids accelerate water absorption. Furthermore, not all CH are absorbed in the same
amount: maltose is absorbed best; fructose does not use active sodium transport; thus,
its absorption is slower.[10 ] In addition, the intake of fats slows down the emptying and therefore interferes
the rehydration.
Taking into account the exercise duration and intensity, the American College of Sports
Medicine (ACSM) and the Canadian Pediatric Society recommend how liquid should be
replaced during sports practice ([Fig. 1 ]).[35 ]
[44 ]
Fig. 1 Guidelines for proper hydration in sports activity.
The intake of liquids containing sodium after exercise helps rehydration by stimulating
thirst and liquid retention. Nonathletic individuals should avoid a regular intake
of sports drinks containing CH since they can lead to an excessive calorie intake,
increasing the risk of overweight, and tooth decay.[27 ]
Nutrition and Physical Activity: Influence on Child's Health Status
Bone Compartment
Exercise can reduce the risk of fractures through the increase of bone mass accumulated
during growth. This period is the best moment to increase the mineral bone mass up
to 15 to 30%. Studies performed with tennis players suggest that exercise can increase
periosteal apposition, which increases both bone diameter and strength.[45 ] Nevertheless, a poor nutritional intake can lead to a greater amount of fractures
due to calcium deficit or a higher risk of osteoporosis due to having failed to reach
the peak of bone mineralization by the age of 30. An increase in exercise in prepubertal
girls elicited greater bone mineral gains at a range of skeletal sites compared with
postmenarche girls, because pubertal growth spurt is the moment when bones are more
receptive to the benefits of mechanical strain.[46 ]
[47 ]
The type of sport performed affects the bone mineral change. In sports which involve
jumping, such as basketball, bone mass increases in the lumbar spine and the proximal
femur since they are subject to a greater impact.[48 ] However, in activities which do not involve weight bearing, such as cycling[49 ] or swimming,[33 ] no increase in bone mineral density was observed as compared with sedentary individuals,
and it is lower than athletes who perform exercise involving weight bearing.[46 ]
[47 ]
[50 ]
[51 ]
Development and Growth
Sexual maturation can be delayed by the practice of high-performance sports given
that it causes a delay in the transformation of dehydroepiandrosterone (DHEA) in testosterone.
Thus, very intense exercise elicits an alteration in the adrenal–hypothalamus–hypophysis
axis increasing the elimination of DHEA. Indeed, the individual may have adapted to
training and requires a lower amount of DHEA in the organism to face it.[52 ]
On the other hand, there exist menstrual changes among elite athletes which can be
associated to the so-called “female athlete triad.” This triad was described for the
first time in the early 90s and includes amenorrhea, low energy availability with
or without eating disorders, and osteoporosis.[53 ] This triad is clearly documented in the practice of certain sports such as rhythmic
gymnastics. However, it is not fully verified in other sports such as swimming and
volleyball.[54 ] An inadequate hydration and an imbalanced diet might be possible causes of these
menstrual disorders, although there are no studies which confirm these hypotheses.
Many girls and women athletes present hormonal disorders, such as hypoestrogenism,
that play an essential role in the reduction of bone mineral density. In addition,
amenorrhea produces a decrease in the markers of bone remodeling compared with athletes
with regular cycles.[46 ] Regarding growth, malnutrition caused by an incorrect nutrient intake regarding
the level of PA alters the growth hormone (GH) axis. The insulin-like growth factor
(IGF-I) is reduced and peripheral resistance to the GH ends up slowing down growth.
However, with a correct nutrition intake, sports (especially those involving stretching,
such as basketball or volleyball) help to achieve an optimum growth.
Leptin is a hormone synthesized in the adipose tissue that plays an essential role
in bone metabolism. It is considered a protective factor of osteoporotic fractures
because it stimulates the proliferation of osteoblasts and inhibits the proliferation
of adipocytes. Prolonged physical exercise reduces the levels of leptin whereas short
exercise cycles do not modify its levels.[46 ] However, resistance to the action of this hormone can occur at central level, and
it has been described in obese children.[55 ]
Factors Affecting the Performance of Physical Activity
It is currently accepted that PA is beneficial for children of any age. However, one
must be careful while recommending specific sports since they may exceed the physical
abilities of children depending on their age. In the age range of 2 to 5 years, an
important change takes place in the whole organism, body composition, organ size and
maturation, and in the skeletal-muscle system. Moreover, it is the beginning of a
period of integration of functions such as vision, proprioception, and the vestibular
system. Therefore, during this age range, children must perform activities that help
improve and reinforce these abilities, for example running or throwing objects and
avoiding, where possible, competition with other children to ward off frustration.
From 6 to 9 years, the competences acquired in the previous stage continue to improve,
and abilities start to combine. The aim is therefore to perform activities that allow
children to improve these new abilities, introducing a minimum competition between
pairs, such as swimming, cycling, and football. From 10 to 12 years old, girls' and
boys' organisms start to differ, but they can still compete against each other. Certain
children of this age range already master complex motor activities. In addition, there
is a greater understanding of strategy, and sports involving it are recommended. Pubertal
development appears in early adolescence (13–15 years) and can make children stand
out in a specific sport. Boys who develop earlier are taller and stronger than most
children of their age, which gives them an advantage in sports like basketball or
ice-hockey, or girls who develop later have narrower shoulders that make gymnastics
easier. The recommendation of a specific PA must be determined both by the level of
psychomotor and physical development and by the extent to which children enjoy it,
which depends on several factors—family and educational environment and coaches.
Personal relationships, both social and in the school setting, stand out among the
factors affecting eating habits and PA. At a preschool level family cohesion, parental
influence and control are related in a positive way, even though no results were found
in the relationship between PA and eating habits. At a school level, the socioeconomic
status of teachers has been associated to a greater sports practice. Regarding eating
habits, no school factor seems to affect them.[56 ]
The child's environment, the appearance of the neighborhood, the availability of sports
centers, and how easy these are to access have shown a positive correlation with PA.
Among social factors, it can be highlighted that the culture of PA has a positive
relation with regular PA, and, on the contrary, sedentary practices relate to inadequate
eating habits.[56 ]
Nonetheless, there are differences between schoolchildren and adolescents regarding
sports habits. While adolescents find their parents' socioeconomic status more important,
schoolchildren place more importance on their parents' participation in the activity
to achieve a greater adherence to its performance.[56 ]
Other studies have related PA and nutrition to age, sex, BMI, and other sociodemographic
factors. Boys and girls aged 5 have the same probability of exercising, whereas from
6 to 7 years onward, PA decreases in girls while it remains steady in boys. This calls
for an earlier introduction to sports in girls to avoid overweight and obesity.[57 ]
[58 ]
[59 ] Regarding nutrition, as children get older, there is a greater probability of following
correct guidelines for fruit and vegetable intake but also a greater probability of
consuming sugary drinks.[60 ]
[61 ] Other factors, such as parents' university education, lead to a better nutrition
although it does not significantly increase the intake of fruits and vegetables.[62 ]
[63 ]
