Preface
1.4 Physical Activity, Health and Nutrition
1 Specific Aspects of Childhood Nutrition
Key Words
Adiposity · Bone mineral accrual · Metabolic syndrome · Fitness · Strength · Weight status
Key Messages
• Physical activity (PA) is a behavior that changes with growth and maturation
• Regular PA favorably influences bone mineral accrual, cardiorespiratory fitness, and muscular strength and endurance
• PA has relatively small effects on lipids and adipos- ity and blood pressures in normal-weight and nor- motensive youth, respectively
• PA interventions favorably influence adiposity in the obese, blood pressures in the hypertensive, and components of the cardiometabolic profile in obese youth
• Many indicators of health and fitness, especially metabolic risk, are affected by obesity. A key issue is the prevention of unhealthy weight gain early in childhood and the potential role of PA
© 2015 S. Karger AG, Basel
Introduction
Physical activity (PA) is a behavior. It is the most variable component of energy expenditure. On average, PA declines from late childhood through adolescence, and boys are more active than girls.
From a public health perspective, PA is a be- havior with important implications for health promotion and disease prevention during child- hood, adolescence and adulthood. Emphasis is largely placed on the level of PA associated with health benefits. The role of PA as a medium for learning, enjoyment and social interactions is of- ten overlooked.
Correlates of PA among children and adoles- cents include biological and cultural factors and their interactions. Physical fitness, specifically cardiorespiratory fitness (CRF), is both a corre- late and outcome of PA. Movement skills are also an important correlate of PA. Types and settings (contexts) of PA are often overlooked, and include play, physical education, exercise, sport, transport and chores, among others. Contexts per se and meanings attached to them vary with age and also between and among different cultural groups [1] . Sport is a major context of PA for youth, but regu- lar PA is not equivalent to training for sport.
Outcomes
Two questions, among others, are central to dis- cussions of PA and health of school-age youth:
(1) What are the health and fitness benefits of regular PA?
Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 68–71 DOI: 10.1159/000360318
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(2) What type and amount (frequency, intensity and duration) of PA is needed to bring about these benefits?
Allowing for variation among and limitations of studies, health benefits of PA are summarized in table 1 . Data addressing the first question are largely derived from comparisons of active with less active youth and from studies of specific PA programs. Data addressing the second question are derived from experimental and intervention-
al programs which varied to some extent in set- ting (schools, recreation centers, etc.) and in du- ration, type and amount of PA. In general, the majority involved protocols of moderate-to-vig- orous PA for 30–45 min, 3–5 days per week. Du- rations of programs varied to a greater extent.
Programs in studies on bone health were more variable: moderate-to-vigorous PA 2–3 days per week, 45–60 min of weight-bearing activities and/or 10 min of high-impact activities [2] .
Table 1. Summary of trends in studies on relationships of habitual PA to selected indicators of health status and of the effects of specific PA programs (experimental, interventional) on indicators of health status
Health indicator Relationships to PA Effects of specific PA programs Adiposity Normal weight: less adiposity in habitually
active youth
Normal weight: minimal effect
Overweight/obese: reduction in overall and central adiposity with PA interventions Bone Increased bone mineral content in active
youth
Variety of PA programs: increased bone mineral content and bone strength Lipids and
lipoproteins
Habitual PA: weak associations with TC, HDL-C, LDL-C and triglycerides
Weak beneficial effect of MVPA on HDL-C and triglycerides; no effect on TC and LDL-C Blood pressures Normotensive youth: no clear association
between habitual PA and blood pressures
Hypertensive youth: aerobic PA programs favorably influence blood pressures Mild essential hypertension: suggestive beneficial effect
Cardiovascular health
Habitual PA: weak associations with levels of fibrinogen and C-reactive protein;
inconclusive for endothelial function
Obese youth: aerobic PA programs improve resting vagal tone (heart rate variability) Metabolic syndrome
– cardiometabolic complications
High PA and CRF: better metabolic profile;
association stronger for CRF than for PA
Overweight/obese youth: improved metabolic profile with PA intervention CRF Habitual PA associated with higher CRF Experimental PA programs: favorable
influence on CRF; gains of approx. 10%
(3–4 ml/kg/min) Muscular strength
and endurance
Habitual PA: not consistently related to muscular strength and endurance
Experimental PA programs: significant gains, which vary with protocol – larger gains in strength with high resistance and low repetitions, larger gains in endurance with low resistance and high repetitions Collated from several sources [2–4, 7–15]. TC = Total cholesterol; HDL-C/LDL-C = HDL/LDL cholesterol; MVPA = moderate-to-vigorous PA.
70 Malina
Activity protocols in studies on CRF and mus- cular strength and endurance approximated sys- tematic training. Allowing for variation among studies, protocols for CRF involved continuous PA (approx. 80% of maximal heart rate) for 30–45 min, 3 days per week for 12–16 weeks in youth 8 years of age through adolescence [2] . Protocols for muscular strength and endurance involved progressive resistance activities incorporating re- ciprocal and large muscle groups for 30–45 min, 2–3 days per week, with a rest day between ses- sions, over 8–12 weeks in youth 6 years of age through adolescence [3] .
Individual differences in growth and matura- tion are confounding factors in evaluating effects of PA on health. Indicators of interest change with normal growth and maturation, and several (bone mineral accrual, CRF, strength, HDL cho- lesterol and adiposity) have growth patterns which are variable during adolescence [4] . Sev- eral studies highlight an important role for PA during the interval of maximal adolescent growth that includes peak height velocity. Longitudinal data suggest enhanced effects of PA on bone min- eral accrual [5] and maximal aerobic power [6]
during the interval of maximal growth in both sexes.
Data dealing with bone health are largely on prepubertal children (both sexes) and early pu- bertal youth (primarily girls). Among older ado- lescents, the influence of PA is more variable but generally positive.
Indicators of cardiometabolic health are cur- rently of major interest: low HDL cholesterol, high triglycerides, elevated blood pressures, im- paired glucose metabolism, insulin resistance, obesity and abdominal obesity, among others.
The indicators tend to cluster within individuals and compose the metabolic syndrome. Higher levels of PA and CRF are independently associ- ated with favorable metabolic profiles. Adiposity is an additional independent risk factor; leaner youth with low central adiposity (waist circum- ference) have a more favorable profile [7] . Rela-
tionships are stronger for CRF than for PA [8] , but interactions of PA and CRF affect profiles [9] . PA interventions favorably alter risk profiles of overweight/obese youth, but not all individuals respond in the same manner [10–12] . Beneficial effects may be reduced or reversed after program cessation [13] .
The preceding is derived from studies on nor- mal-weight and overweight/obese youth in devel- oped countries. Obesity is a consequence of an imbalance between energy intake and expendi- ture. Evidence dealing with PA of obese youth is equivocal, but the obese tend to have deficient movement skills and physical fitness [4] . The re- sults highlight a need for critical evaluation of correlates of food intake, PA and physical inactiv- ity among obese youth. Physical inactivity is a be- havior independent of PA [1] .
Chronic undernutrition, which is common in many developing countries, is associated with re- duced PA and physical working capacity in school-age youth [4] . Conditions in many coun- tries are changing as they experience the transi- tion from high chronic undernutrition and asso- ciated mortality from infectious and diarrheal diseases to increasing prevalence of overweight/
obesity and of morbidity and mortality from noncommunicable, degenerative diseases associ- ated with dietary change and reduced habitual PA.
Conclusions
• Regular PA favorably influences bone mineral accrual, CRF and muscular strength and en- durance
• PA has relatively small effects on lipids, and on adiposity and blood pressures in normal- weight and normotensive youth, respectively.
A greater amount of PA may be necessary in healthy youth
• Beneficial effects of PA are more apparent among ‘unhealthy’ youth – on adiposity in the
Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 68–71 DOI: 10.1159/000360318
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obese, on blood pressures in the hypertensive, and on insulin, triglycerides and adiposity in obese youth with the metabolic syndrome • Many indicators of health and fitness, espe-
cially metabolic risk, are affected by obesity. A key issue is the prevention of unhealthy weight gain early in childhood and the potential role of PA [14]
• Interventional/experimental PA studies gen- erally focus on outcomes. There is a need to consider the level of PA needed to maintain beneficial outcomes, as it may differ from that needed to trigger beneficial outcomes
• Most interventional/experimental protocols use continuous PA, except for studies of bone
health and muscular strength and endurance.
Activities of children, especially young chil- dren, are largely intermittent. Potential health benefits of high-intensity, intermittent proto- cols need study
• Activity needs vary with age during childhood and adolescence: young children need variety in PA with opportunities to develop and refine movement skills in the context of free play;
children more proficient in motor skills tend to be more physically active; with the transi- tion into puberty and adolescence, the capac- ity for continuous activities increases and ac- tivity can be more prescriptive with emphasis on health and fitness
12 Nassis GP, Papantakou K, Skenderi K, Triandafillopoulou M, Kavouras SA, et al: Aerobic exercise training improves insulin sensitivity without changes in body weight, body fat, adiponectin, and inflammatory markers in overweight and obese girls. Metab Clin Exp 2005; 54:
1472–1479.
13 Carrel AL, Clark RR, Peterson S, Eick- hoff J, Allen DB: School-based fitness changes are lost during the summer va- cation. Arch Pediatr Adolesc Med 2007;
161: 561–564.
14 Malina RM: Childhood and adolescent physical activity and risk of obesity in adulthood; in Bouchard C, Katzmarzyk PT (eds): Advances in Physical Activity and Obesity. Champaign, Human Kinet- ics, 2010, pp 111–113, 376–377.
15 Physical Activity Guidelines Advisory Committee: Physical activity guidelines advisory committee report 2008, part G, section 9: youth. Washington, US De- partment of Health and Human Servic- es, 2008. www.health.gov/paguidelines.
References
1 Malina RM: Biocultural factors in devel- oping physical activity levels; in Smith AL, Biddle SJH (eds): Youth Physical Activity and Inactivity: Challenges and Solutions. Champaign, Human Kinetics, 2008, pp 141–166.
2 Strong WB, Malina RM, Blimkie CJR, Daniels SR, Dishman RK, et al: Evidence based physical activity for school-age youth. J Pediatr 2005; 146: 732–737.
3 Malina RM: Weight training in youth:
growth, maturation, and safety – an evidence-based review. Clin J Sport Med 2006; 16: 478–487.
4 Malina, RM, Bouchard C, Bar-Or O:
Growth, Maturation, and Physical Ac- tivity, ed 2. Champaign, Human Kinet- ics, 2004.
5 Bailey DA, McKay HA, Mirwald RL, Crocker PRE, Faulkner RA: A six-year longitudinal study of the relationship of physical activity to bone mineral accrual in growing children: the University of Saskatchewan Bone Mineral Accrual Study. J Bone Miner Res 1999; 14: 1672–
1679.
6 Mirwald RL, Bailey DA: Maximal Aero- bic Power. London, Sport Dynamics, 1986.
7 Ekelund U, Anderssen SA, Froberg K, Sardinha LB, Andersen LB, Brage S: In- dependent associations of physical ac- tivity and cardiorespiratory fitness with metabolic risk factors in children: the European Youth Heart Study. Diabeto- logia 2007; 50: 1832–1840.
8 Rizzo NS, Ruiz JR, Hurtig-Wennlöf A, Ortega FB, Sjöström M: Relationship of physical activity, fitness, and fatness with clustered metabolic risk in children and adolescents: The European Youth Heart Study. J Pediatr 2007; 150: 388–394.
9 Brage S, Wedderkopp N, Ekelund U, Franks PA, Wareham NJ, et al: Features of the metabolic syndrome are associated with objectively measured physical activ- ity and fitness in Danish children: the European Youth Heart Study (EYHS).
Diabetes Care 2004; 27: 2141–2148.
10 Gutin B, Barbeau P, Litaker MS, Fergu- son M, Owens S: Heart rate variability in obese children: relations to total body and visceral adiposity, and changes with physical training and detraining. Obes Res 2000; 8: 12–19.
11 Gutin B, Yin Z, Johnson M, Barbeau P:
Preliminary findings of the effect of a 3-year after-school physical activity in- tervention on fitness and body fat: the Medical College of Georgia Fitkid Proj- ect. Int J Pediatr Obes 2008; 3(suppl 1):
3–9.
1 Specific Aspects of Childhood Nutrition
Key Words
Metabolic programming of long-term health · Developmental origins of adult health · Breastfeeding and obesity · Perinatal nutrition · Disease risk prevention
Key Messages
• Nutritional and metabolic factors during sensitive, limited periods of early human development have a long-term programming effect on health, well- being and performance in later age, extending into adulthood and old age
• Evidence for early programming effects arises from in vitro experiments, animal models, retro- and pro- spective epidemiological studies and controlled in- tervention trials
• Obstetric and paediatric medicine are expected to achieve a much greater role for the prevention of long-term disease risks in the population
• The important effects on health of early nutrition programming justify major investments into re- search and improvement of practice
© 2015 S. Karger AG, Basel
Introduction
Epidemiological studies, numerous animal mod- els and clinical intervention trials provide ample evidence that nutritional and metabolic factors
during sensitive, limited periods of early human development have a long-term programming ef- fect on health, well-being and performance in lat- er age, extending into adulthood and old age [1–
3] . Biological programming is defined as lasting effects on physiology, function, health and dis- ease risks induced by environmental cues during limited time periods of early development and plasticity. While the term ‘programming’ was in- troduced into the scientific literature by Dörner [4] already in 1974, the concept has received broad attention primarily due to retrospective epidemiological studies published by Barker and others documenting inverse relationships be- tween body weight at birth and at 1 year of age, respectively, and the risks of hypertension, diabe- tes and coronary heart disease ( fig. 1 ) in adult- hood [5, 6] . These observations stimulated inten- sive research that demonstrated powerful long- term effects of nutrition and growth before and after birth on later health, performance and dis- ease risk. The exploration of underlying mecha- nisms and the resulting effects of metabolic pro- gramming offers tremendous opportunities for the early prevention of major health risks already during pregnancy and infancy, and they could provide both obstetric and paediatric medicine with a markedly increased role in promoting the long-term health of the population. It is likely that
Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 72–77 DOI: 10.1159/000369235