Breastfeeding and Obesity

November 28th, 2012 by MorganDowney Leave a reply »

Breastfeeding has long been considered to be protective against the development of adult obesity in the child but a causal relationship has been difficult to establish. Early Life Determinants Evidence from epidemiological research indicates that overweight and obese women are less likely than normal weight women to initiate breastfeeding or maintain it for shorter durations. However, whether this is due to biological, psychological or cultural reasons is unclear.  Systematic Review of maternal obesity and breastfeeding The Growing Up Today Study of 15,000 children showed that, if breastfed longer than seven months, a child was less likely to be obese. Overweight Adolescents and breastfeeding More recent studies appear to mute the benefit of breastfeeding vis a vis child’s adult weight. A study of over 7,000 children found the effects vanished when other factors, such as parental smoking, education and age were analyzed. Exclusive breastfeeding of Swedish children Most recently, a randomized trial of breast feeding promotion in Belarus of 17,000 infants raised the rates of breastfeeding but had no effect on weight. Randomized breast-feeding trial in Belarus

However, reliance on this advice may be misplaced. According to an update of a Cochrane Review, Optimal Duration of Breastfeeding.

“Exclusive breastfeeding for six months versus three to four months, with continued mixed breastfeeding thereafter) reduces gastrointestinal infection and helps the mother lose weight and prevent pregnancy but has no long-term impact on allergic disease, growth, obesity, cognitive ability or behavior. ..A reduced level of iron has been observed. ..

The epidemiologic evidence is now overwhelming that, even in developed countries, breastfeeding protects against gastrointestinal and (to a lesser extent) respiratory infection, and that the protective effect is enhanced with greater duration and exclusivity of breastfeeding. Prolonged and exclusive breastfeeding has also been associated with a reduced risk of the sudden infant death syndrome and, in preterm infants, necrotizing entrerocolitis. Breastfeeding is life-saving in developing countries; a meta-analysis reported markedly reduced mortality (especially due to infectious disease) with breastfeeding even into the second year of life…

The evidence of long term effects of breastfeeding on obesity and mean body mass index (citations omitted) or blood pressure, type 1 or type 2 diabetes, or ischemic heart disease is also weak.

Importantly, they comment on the possibilities of bias in the scientific evidence, stating,

Most of the scientific evidence on the health effects of breastfeeding has been based on observational studies, with well-recognized sources of potential bias. Some of the biases tend to favor exclusively breastfed infants, while others favor those who receive earlier complimentary feeding. Reverse causality is an important potential source of bias. Infants who continue to be exclusively breasted tend to be those who remain health and on an acceptable growth trajectory; significant illness or growth faltering can lead to interruption of breastfeeding or supplementation with infant formula or solid foods. Infants who develop a clinically important infection are likely to become anorectic (loss of appetite) and to reduce their breast milk intake, which can in turn lead to reduction in milk production and even weaning. The temporal sequence of the early signs of infection and weaning may not be adequately appreciated; infection may be blamed on the weaning, rather than the reverse. Advanced neuromotor development may also lead to earlier induction of solid foods, which could then receive ‘credit’ for accelerating motor development.  Poorly-growing infants (especially those in developing countries) are likely to receive complementary feedings earlier because of their slower growth. In developing countries, however, rapidly-growing infants may require more energy than can be met by the increasingly spaced feedings typical of such settings. This may result in crying and poor sleeping, supplementation with formula or solid foods, or both, reduced suckling, and a vicious cycle leading to earlier weaning. ..

Finally, the underlying assumption in this field has been that ‘one size fits all’, i.e. that average population effects can be applied to individual infants. There has been little discussion of the fact that all  infants, regardless of how they are fed, require careful monitoring of growth and illness, with appropriate interventions undertaken whenever clinically indicated.”

In case you haven’t noticed, our pubic health leaders push policies which are virtually 180 degrees away for the Cochrane conclusion. Why such a discrepancy between the highly-regarded Cochrane review and US public health authorities

In May 7, 2012, Health and Human Services Secretary Kathleen Sebelius told the audience at the Weight of the Nation conference, that, in regard to obesity, “ We know that a mother’s health during pregnancy and decisions like whether or not to breastfeed, can have a huge impact on both the mother and child’s health. And these impacts last a lifetime.”  HHS:Speeches:Sebelius: Weight of the Nation

Genetic studies may clarify the mixed outcomes of many studies. Laurent Briollais and colleagues in Canada and Australia have studied 1,096 Australian children from birth to 14 years of age. They found that the presence of the risk allele of the FTO gene, SNP rs9939609. In girls, exclusive breastfeeding for three months interacts with the SNP at baseline and can reverse the increase in BMI. In boys, exclusive breastfeeding reduces BMI in both carriers and non-carriers of the SNP. Six months of exclusive breastfeeding put the boys’ BMI growth curves back to the normal range. If validated by other studies, this finding could bring a new dimension to the breastfeeding and obesity issue.Impact of breastfeeding on  FTO-related BMI


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