increase of its prevalence in the past 20 years strongly suggests that environmental
factors are primarily responsible. The history of humanity during the past
20y ears has seen a radical and extremely rapid evolution of the environment. This
swift change precludes any possibility of genetic adaptation and should be countered
by a rapid and lasting change in behavior. The wealth and variety of food
supply available 24 h a day and throughout the year, the change in food dietary
properties, the lack of cultural references and the abundance and diversity of information,
all create a ‘toxic’ environment responsible for obesity and eating habit
disorders. Obesity is part of a consumer and profit system to the detriment of individuals’
health. The current economic cost associated with the frequency of the
illness and its morbid complications leads to believe that the money spent is less
than the economic profit made. A sudden change in political opinion has occurred
and should facilitate and stimulate intervention on behavior and the environment.
The variety of environmental factors involved, their intricacy and mechanisms
are extremely complex. We will discuss the most important factors for
children in our view namely the influence of television and advertising, eating
habits, dietary preferences and psychosocial factors. These factors are involved
in one or several of the physiopathological mechanisms of obesity, i.e. diet,
inactivity and physical activity, psychosocial factors.
Effect of Television
Television plays an important role in children’s socialization [1]. Most
households have at least one television [2]. Television and its possible role in
the development of pediatric and adolescent obesity has been an important
research focus in trying to characterize the underlying causes of the obesity epidemic.
Many, but not all [3–4], studies document cross-sectional and prospective
relations between greater TV watching and higher childhood obesity, even
after controlling for confounding factors such as socioeconomic status. A longitudinal
study (from 1990 to 1996) shows that childrens’ overall TV watching
increased with no evidence of differential change over time by gender or ethnicity.
This increase occurred for weekdays and weekend days and there was no
significant difference between seasons. The number of meals per week children
ate while watching TV increased over time, along with the number of TVs in the
home. The percentage of children with TVs in their bedroom and the percentages
of homes with a VCR records have increased [5]. Mean TV/video viewing
time increases with the child’s age. Interestingly the prevalence of obesity has
increased by 1.06–2.5% per hour of TV a day [1–2]. TV hours are significantly
related to BMI; however, BMIs are only significantly different between children
watching less than 2 h of TV/day and those watching more than 2 h of TV/day
and this only in older children. Another study reports that 40% of children had
a TV in their bedroom and showed that these adolescents were more likely to
be overweight and spent more time (4.6 h/day) watching TV [2].
The number of hours of TV watching in children is also correlated with the
number of meals taken while watching TV and the number of hours of TV
watching in parents. Interestingly, there was a discrepancy between the reports
filled in by children and those filled in by parents with a tendency of parents to
under report. Higher maternal education was also associated with less TV viewing
early in childhood but not significantly in older children. The role of
ethnicity and social income was also reported in conflicting data. Some studies
reported a correlation between adiposity and TV viewing in children in low and
middle income school districts, while others showed a significant difference
between black and Hispanic and white children with a higher TV video viewing
in the formers.
Therefore, the number of hours watching TV is probably an important
factor in childhood obesity. How does it work?
Does TV Viewing Influence Children’s Physical Activity?
Gortmaker et al. [6, 7] agree that activity and inactivity represent distinct
domains that could independently affect the prevalence of obesity.
Is pediatric overweight primarily linked to reduced time spent in vigorous
physical exercise (activity play and sports) or to increased time spent in sedentary
activity? In most of the studies reported, a stronger association has been
found between BMI and time spent watching TV [8–10] than between BMI and
physical exercise. Moreover, intervention studies focused only on reduction of
TV viewing in children were more effective for weight loss than those focused
on increased physical exercise [11–12]. Interestingly, the causal role of TV
watching in childhood obesity is also confirmed by the fact that small movements
(fidgeting) are suppressed when children watch TV thereby reducing
energy expenditure by itself, and this effect may be emphasized for long periods
of TV watching [13]. Consequently TV watching acts as a sedentary behavior
associated with a very low energy expenditure.
Food Advertising on Television
Television is the largest single media source of messages about food with
over 75% of food manufacturers’ advertising budgets. The food products advertised
most intensively on TV tend to be overconsumed whereas fruit and
vegetable which are never advertised are underconsumed [14]. Although televised
food advertising targets all age groups, food products are the most heavily
promoted category targeting young children [15, 16–18]. Food advertisements
account for well over 50% of all advertisements targeting children on national
network and food is the most frequently advertised product category on children’s
TV. It has been estimated that children view an average of one food
commercial every 5 min [19–22]. Besides these food advertisements, advertisements
for fast food chains have strongly increased in the USA and in Europe
during the last 10 years reaching almost a third of all food advertisements in
the USA.
The fact that young children are the most targeted population for TV food
advertisements reflects marketing analysts’ belief that food habits developed in
childhood influence lifelong consumption patterns [15, 23–24] and that parents
accommodate children’s food requests.
The nutritional quality of the foods being advertised on children’s TV
remained consistently focused on high-sugar content foods (69%), high fat
(35–40%) and high sodium content foods (17–20%) [22].
Besides the poor nutritional quality of TV food advertisements, it is important
to know that they may mislead children about nutritional attributes of food
products. Moreover, TV program contents are also an important source of food
messages showing behaviors where food is not used to satisfy hunger but to
reward or punish oneself or another person or to relieve tension in social encounters.
In these movies, despite obviously poor food habits actors were always thin
and beautiful [25–26].
Effects of TV Food Advertising on Children’s Food Behaviors
Interest in the topic has recently been revived [27] showing that children
exposed to advertising will choose advertised food products at significantly
higher rates than non-exposed children [27, 28]. Moreover, two studies showed
that exposure to food advertising increased the total energy intake and their
choice of candy over fresh fruit for snack. Another impact of TV food advertisements
is how children influence their mother’s purchases while shopping.
Children exposed to TV food commercials made more attempts to influence
their mother’s product and brand purchase, and this effect is stronger if the
mother watched food advertisements with the child. Along the same lines, mothers
watching more TV are more compliant to food requests. The more the children
watched TV the more they tried to influence their mothers and 61% of all
purchase requests were for food items [24]. Some studies suggest that children’s
requests for different categories of non food products vary according to child
age while requests for cereals and snack foods remain constant across all age
groups [22, 24], and that parental compliance was higher for food items.
Interestingly, family use of TV also influences children’s consumption patterns,
children from families with TV on during 1 or 2 meals per day consumed significantly
less energy from carbohydrate and tended to consume more energy from
fat than others [29].
Association between TV and Children’s Dietary Intake
After adjusting for age, BMI, race, family income and physical exercise
total energy intake has been found to be positively associated with number of
TV viewings per day among girls [9], though for boys it was not significantly
different. Another study showed that TV viewing is related to overall energy
intake and dietary fat intake [30]. The amount of TV viewed by children is
significantly related to their consumption of sweet and salty snacks both at home
and at school. An intervention study targeting the reduction of TV viewing [31]
showed the complexity of this issue. Four dietary behaviors were used for outcome
measures: number of meals eaten in front of the TV, frequency of snacking
while watching TV, daily serving of high foods and daily serving of highly
advertised foods. The intervention led to a decrease in the number of meals eaten
while watching TV and a tendency to reduce daily high-fat food servings.
Other Related Factors to TV Watching and Obesity
In some studies [32] family income has been reported to be associated with
TV viewing, with children from low and middle income more affected by TV
watching. These results have not been reported in all studies. In a study of low
income preschool children, TV viewing was significantly related to the prevalence
of child overweight. In other studies involving children and adolescents,
black children spent more time watching TV/video than white children.
Moreover TV viewing seems to be related to parental education.
An Italian study of children aged 2 through to 8 years reported that less
educated mothers have a more positive attitude towards TV than higher educated
mothers, who were more likely to prohibit certain shows and monitor their
child’s TV use [33]. Race/ethnicity, income, educational attainment, employment
are confounding factors in the interpretation of the involvement of factors
associated with TV watching. Lower cognitive function and, particularly in this
issue, uncritical exposure to messages on TV and choice of TV programs represent
other factors which could influence the role of TV watching. Nevertheless,
two recent clinical trials in relatively high educated populations demonstrate
that reductions in TV/video viewing were associated with reduction in adiposity
[34, 35].
Nowadays most studies suggest that TV is partly responsible for the
increasing prevalence of obesity in children and adolescents through different
pathways: increasing sedentary activity, total energy intake, promoting poor
eating habits and consumption of poor nutritional products through food
advertisements. Family habits are important factors regulating the effects of TV
viewing in children through media-habit, lifestyle habits, culture, income and
educational levels. Given that the combination of lifestyle factors are associated
to heavy TV use, pediatricians should advise parents about the potentially
harmful effect of excessive TV use on their children’s nutritional health.
Eating Behaviors
Early Experience with Foods
The knowledge of which behavioral factors influence energy intakes, food
preference and food intake control could suggest some strategies for preventive
interventions.
One of the first choices that parents make that shapes a child’s experience
with food and flavors is the choice to breast-feed or formula-feed. There are
some data supporting the idea than this early experience with flavors on milk
has an effect on milk intake and in later food acceptance [36, 37]. On a short-term
basis, it has been demonstrated that flavors in breast milk influence infant’s
consumption and time attached to the maternal nipple [38, 39].
Interestingly infant adiposity has been related to nutritive sucking style
[40], which could be due to specific sensitivity to some flavors. In rats it seems
that rat pups learn to prefer their mother’s diet due to the flavors of the milk.
Formula-fed babies have experience with only a single flavor versus breast-fed
babies. In humans, very limited evidence suggests that the varied flavor experience
of breast-fed infants can facilitate acceptance of solid foods during the
weaning period [41], with breast fed infants showing greater initial acceptance
of new foods. This finding is consistent with those showing that early experience
with a variety of flavors leads to more ready acceptance of new foods later [42].
Subsequently, infant dietary experience is shaped by infant-feeding decisions
and dietary patterns of the mother and it provides the basis for food acceptance
and patterns of intake in infancy. Except for sweet and salty foods infants
and children are predisposed to be neophobic and reject new foods which can
be overcome after 5–10 exposures. These findings emphasize the importance of
early experience with food and food acceptance, showing that children come to
like and eat what is familiar.
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