Babies are all born with an in-built, near-perfect, appetite control mechanism, so why are there so many obese children in our schools? by Jo Carlowe
Data from the Health Survey of England reveals that 31% of boys and 29% of girls aged between 2-15 years old are currently overweight or obese.[i] According to The Early Bird Study in the Journal Pediatrics, [ii] most of this excess weight is gained before the age of five.
In establishing the causes of childhood obesity, experts cite factors ranging from sedentary lifestyles through to the mother’s diet during pregnancy. But most recently, the spotlight has shone on the months immediately after birth when the baby is drinking an exclusive diet of either breast or formula milk. The thinking now is that this time is crucial in determining future eating habits and body weight.
Just as there are critical periods in brain development that allow babies to reach milestones such as the ability to track movement with their eyes or acquire language, so there is now mounting evidence that babies also have a ‘developmental window’ in which to set their appetite. If during this period the baby’s natural ability to self-regulate food intake is overridden, the infant will likely put on weight rapidly, setting into motion biological and behavioural changes that will predispose him to a lifelong fight against flab.
Many studies support the theory that faster growth in infancy (measured by upward percentile crossing for weight or length on baby charts) increases the risk of obesity, cardiovascular disease, raised blood pressure, stroke and type 2 diabetes later in life.
In a British Medical Journal paper, the researchers note that obese babies have ten times the risk of being obese later in life. More tellingly, it’s not just obese babies that risk future weight gain, but rather infants who grow rapidly during their first few months of life (even if not obese). The findings reveal that such babies have six times the risk of future obesity.[i]
Scientists across the world are starting to back-up these findings. Dr Nicholas Stettler, Nutrition Fellow at The Children’s Hospital of Philadelphia, USA, estimates that 20% of the risk of obesity at the age of 7 years can be attributed to having a rate of weight gain in the highest quintile in the first 4 months of life.[ii] While a similar study from Holland shows that babies who gain weight rapidly in the first three months or life are significantly more likely to be obese by the age of 19.[iii]
These papers on human infants lend weight to animal research dating back to the 1960s. In one study, rats raised in small litters, that fed more in the suckling period than those in bigger litters, were larger as adults.[iv] Likewise, baboons that were overfed in infancy had greater fat mass in adulthood.
Yet when in 2004 Professor Atul Singhal, of the Childhood Nutrition Research Centre at the Institute of Child Health, University College London, published a paper in the Lancet to suggest the same held true of humans, it was met with criticism.[v]
“There was this idea that there is no such thing as too much growth in babies,” says Professor Singhal.
Yet the impact of this overfeeding is substantial. Professor Singhal and colleagues had assigned babies to a regime in which half received a standard formula and half a growth-promoting formula. In a second study, he compared formula fed babies to breast-fed ones. The results were stark – 6-8 years later the breast fed babies had healthier levels of fat in their bodies and better blood-pressure readings than the formula-fed one. Similarly, the fat mass in the children randomly assigned the nutrient-enriched formula was 22-38% greater than in those who received the standard formula. [i]
Singhal’s findings support the idea that if babies grow at a steady, rather than accelerated, pace during their first months of life are at less risk of obesity and associated health problems than those who grow rapidly.
So why do these large, some might say ‘bouncing’ or ‘bonny’ babies face a greater risk of obesity later in life simply by growing so well early on?
Singhal says this rapid growth sets into train a series of biological changes that cannot be reversed. In essence, this early weight-gain sets down the biological blueprint of how that child will regulate food intake and appetite throughout its life. Hormones such as insulin and leptin - both related to appetite regulation - will be affected.
Consistent with this, is Singhal’s finding that later insulin resistance (a risk factor for type 2 diabetes) is greatest in infants who experience accelerated growth in the first two weeks of life.
Moreover, the speed and ease with which bottle-fed babies acquire their milk, may exacerbate the problem.
Most experts agree that breastfed babies have to work 'harder' for their feed. Bottle feeding by contrast is easier and quicker. This is particularly true of babies fed with vented anti colic bottles which are ‘almost free-flow’. The risk is that the baby takes in milk so quickly that there is no time for its brain to register that it is satiated (a process that is thought to take around 20 minutes).
During this time, receptors inform the brain that your body is receiving nutrients by sending hormone signals. The hormone cholecystokinin is released by your intestines and the hormone leptin tells your brain about your long-term needs and overall satiety based on how much energy your body is storing. If you eat too fast, these hormones may not have enough time to properly communicate.
Clinical Psychologist Dr. Barbara Pearlman, specialist in eating disorders and early mother-child communication, explains: “The information from the stomach to the brain takes time to say: ‘I’m full’."She says with bottles, the tummy often fills up before the brain has time to register that the baby is satiated.
"The message from the stomach being full to the brain takes 20 minutes. People who eat fast don’t yet know they are satisfied. A baby that sucks longer [because they are working hard for a feed] has time to say: ‘yes I’m full’."
So babies can put on too much weight because they are fed formula-milk that is too rich and/or take from bottles that deliver milk too quickly to allow natural appetite-control hormones to kick-in. But that’s not the whole story.
Ironically, babies are born with an innate, near-perfect appetite control mechanism.
Lactation expert, Dr. Mike Woolridge, of Leeds School of Healthcare, says babies are so good at appetite regulation that ‘if you mess them around’ by getting them to feed from only one breast exclusively or swapping them between breasts before they have got to the rich breast milk at the end of a feed, or by switching bottle-fed babies between high and low calorie formulas - in all cases, left to their own devices, the babies self-regulate. The ones on the breast regime take more milk when on the less rich two-breast regime, and less when on the one breast richer milk regime. While the formula-fed babies similarly adjust, taking in the same amount of calories but in different volumes.
So why then do formula-fed babies seem to lose this skill? The answer is simple. As parents we condition our babies to overfeed and more often than not, it’s a classic case of ‘killing with kindness’.
"The guidelines suggest a range of number of ounces per pound of weight to be consumed by the baby per day. However, if the baby takes less, new mums may get very worried and disregard that the baby is chubby and doing well. If parents are insecure they might over rely on the guidelines rather than understanding that these are general and need not be interpreted rigidly.
“If baby is the right weight for height, the mother is doing all the right things. The baby will tell you. The mother should always follow the baby. When mothers get very anxious they don’t hear the baby. ”
Registered nutritionist Julia Wolman says it’s a ‘natural instinct’ for parents to want their babies to ‘grow well’.
“Growing well to many parents means growing fast. Many parents feel it’s a sign that they are doing a good job if their baby is gaining weight quickly.”
She says this was particularly problematic with the old (pre-2009) growth charts that parents received in their child’s red book.
“The 50th centile was highlighted in bold. This often led parents to believe that if their child was ‘normal’ or ‘healthy’ their weight would track along this line. The new growth charts have been designed with a de-emphasised 50th centile line.”
Another welcome change has been an overhaul in baby formula. Manufacturers have reduced the levels of growth-enhancing proteins in their formulas.
Even so, parents can override this by adding scooped instead of level spoonfuls, or by widening the teat of the baby’s bottle (with a red-hot needle) so the baby feeds too fast.
In an ideal world these scenarios would be eliminated because every mum would breast feed. We know ‘breast is best’ - there is a 4% reduction in obesity risk associated with every month that the mum breastfeeds.[i]
But it is impractical, unrealistic and fantastical to anticipate a universal switch to breastfeeding. According to the Infant Feeding Survey (UK 2010)[ii] while 69% of mothers exclusively breastfed at birth, within a week less than half were still doing so (46%). Within six weeks almost three-quarters of mothers (73%) had given their baby milk other than breast milk and by six months only 1% of mothers were exclusively breast-feeding.
So if childhood obesity is to be tackled then strategies need to be devised that help all babies to grow steadily regardless of how they are fed.
Recognising that a high percentage of mothers still choose to bottle feed, doctors are being pragmatic but not complacent. Paediatric experts say if babies are to continue to be bottle fed then ‘everything must change’. The weight gain of bottle-fed babies must be brought in line with that of breastfed babies.
For their part, the formula manufacturers are continuing to develop products that don’t promote rapid growth and health visitors are starting to spread the word that big is not beautiful.
But for change to really occur the message has to filter down to parents.
“Bigger babies are not necessarily healthy. Once you convince mothers of that then the whole philosophy changes,” says Professor Singhal.
“If a baby is crossing percentiles upwards, the first thing I say to mums is ‘you don’t need to be worrying about feeding your baby. Your baby is doing more than well enough. It’s putting on too much weight.’ You’re not saying ‘put the baby on a diet’ but rather telling the mother not to worry about her baby’s milk intake.”
The fact is - babies are born with the ability to regulate their energy intake and it’s up to us as parents to respect and nurture this.
[ii] Gardner DS, Hosking J, Metcalf BS, Jeffery AN, Voss LD, Wilkin TJ. Contribution of early weight gain to childhood overweight and metabolic health: a longitudinal study (EarlyBird 36). Pediatrics. Jan 2009;123 (1):e67-73.
[iv] Stettler N, Stallings VA, Troxel AB, et al. Weight gain in the first week of life and overweight in adulthood: A cohort study of European American subjects fed infant formula. Circulation 2005;111:1897–903.
[v] Holzhauer S, Hokken Koelega AC, Ridder M, et al. Effect of birth weight and postnatal weight gain on body composition in early infancy: The Generation R Study. Early Hum Dev. May 2009;85(5):285-290.
[viii] 2010: Atul Singhal; Kathy Kennedy; Julie Lanigan; Mary S Fewtrell; Tim J Cole; Terence Stephenson; Alun Elias-Jones; Lawrence T Weaver; Samuel Ibhanesebhor; Peter D MacDonald; Jacques Bindels; Alan Lucas
The American journal of clinical nutrition 2010;92(5):1133-44.
Jo Carlowe is an experienced freelance journalist and editor.
She writes features and news for national newspapers, consumer magazines, medical and professional journals.