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Consequences of Obesity 199
The vast majority of overweight and obesity is
caused by a higher energy intake (amount of
calories consumed in food and drinks) than energy
expenditure (amount of energy used in growth,
development and activity). The excess energy
intake is stored as extra adipose tissue which
contributes to the physical and metabolic changes
seen in obesity.
Medical causes of obesity in children are
extremely rare and include:
●● endocrine disorders often signalled by short
stature such as hypothyroidism, Cushing’s
syndrome and growth hormone deficiency
●● single-gene defects (e.g. leptin deficiency and
melanocortin 4 receptor (MC4R) deficiency)
●● chromosomal disorders, such as Prader–Willi
syndrome, Bardet Biedl syndrome, Alstrom
syndrome and Cohen syndrome.
Excess weight gain in preschool children is of
particular concern. A Dutch study found poor
lifestyle patterns at 5 years were associated with
later childhood obesity (Gubbels et al. 2011). A UK
study found that most of the excess weight in
9-year-old children had been gained as excess
weight before 5 years of age (Gardner et al. 2009).
As part of the Avon Longitudinal Study of
Parents and Children (ALSPAC), also known as the
‘Children of the 90s’ study, Reilly et al. (2005)
identified the following risk factors for childhood
obesity at age 7 years irrespective of whether the
child was overweight at 3 years or not:
●● parental obesity of one or both parents
●● high birthweight
●● rapid weight gain in the first year – crossing
upwards across weight for age centile lines after ●● increased severity of asthma and other
8 weeks of age
●● catch-up growth between birth and 2 years
●● an early adiposity rebound at 3–4 years of age
when the BMI does not continue to decrease as
expected on BMI centile charts
●● sedentary behaviour: more than eight hours
watching TV per week at 3 years
●● less than 10½ hours sleep/24 hours at 3 years –
normally 3 year olds sleep for about 12 hours in
every 24 hours.
Parental obesity
Having one obese parent increases the risk, and if
that parent is the mother the risk is higher. The
highest risk is in children with two obese parents
(Dorosty et al. 2000, Reilly et al. 2005). This could
be due to a combination of factors: genetic, social or
environmental.
Weight gain in infancy
Whether breastfeeding in early infancy plays a role
in preventing obesity in childhood or not remains
controversial. Formula-fed infants lose less weight
in the first few days after birth and their overall
growth pattern is different to that of exclusively
breastfed babies. As discussed in Chapter 4.1 it is
easier to overfeed a baby by bottlefeeding than by
breastfeeding. However, there are many lifestyle
factors throughout the toddler years and early
childhood, in addition to the mode of milk feeding
during infancy, that may contribute to the
development of obesity (Hediger et al. 2001,
Clifford 2003). Rapid weight gain in the first
3 months in infancy is also related to low socio-
economic status (Wijlaars et al. 2011), which is in
turn associated with a higher risk of obesity.
Adiposity rebound
‘Adiposity rebound’ is the term given to the time
when BMI begins to increase after falling to a low
point at around 5–6 years. Children with an early
adiposity rebound (i.e. whose BMI begins to
increase earlier than 5–6 years) are at higher risk of
obesity.
Consequences of Obesity
The health risks associated with obesity in
childhood are:
respiratory disease
●● lower levels of fitness