Too chubby too soon?
Recent studies show that rapid weight gain during infancy could be a risk factor for future obesity.

Increasing levels of obesity in children in developed countries such as the US and the UK are often referred to in the media and scientific literature. But when it comes to developing countries such as South Africa, the stats are starting to look just as scary: 10-18% of SA children between the ages of 6-13 years are overweight and 2-5% are obese. 

Various charts are available to assess infant growth during the first years of life and any significant change in any of these measures should be watched. 

Babies’ growth is monitored by regularly recording a number of statistics including:
  • weight-for length, a measure of wasting
  • weight-for-age, a measure of underweight or overweight,
  • length-for-age, a measure of stunting.
Stunting is the most common nutritional disorder in South Africa with 1 in 5 children being reported as stunted. But as we become more urbanised, concurrent stunting and overweight, or obesity, is also becoming a concern.

It is well known that prenatal factors such as maternal stress and nutrition during pregnancy have been shown to ‘programme’ the foetus for future disease risk.  More recent scientific literature shows that a rapid increase in weight in the first 1-2 years of life is associated with being overweight or obese as a child, and will also increase the risk of obesity, diabetes and cardiovascular disease in adulthood. 

Recent data from Paediatrics, collected from a large study of pregnant women and their children, reported that the probability of a child being obese at the age of 3 years is 40% if their weight-for-length at 6 months was in the highest quarter, compared to 1% if their weight-for-length was in the lowest quarter.

This was after taking into account factors such as maternal smoking, maternal body mass index (BMI) prior to pregnancy, and weight gain during pregnancy, paternal BMI and other demographic factors.

Further, another study published this year in the Journal of Clinical Endocrinology and Metabolism suggests that rapid weight gain during infancy is also associated with an earlier onset of puberty. 

Early periods for chubby babies

This data showed that for every one unit gain in weight standard deviation score between the age of 1 and 9 months, there was a 34% increased risk of menarche (the onset of the menstrual period) occurring before the age of 12 years. Rapid weight gain in the first 9 months also increased the risk of being overweight at the age of 10 years.  An earlier age at menarche has been associated with a higher risk of obesity in adulthood, an increased risk of adult onset diabetes, increased cardiovascular disease risk markers and pre-menopausal breast cancer.

Extensive nutritional information is available on the many benefits of breast-feeding, when is best to introduce solids etc, and the role of various nutrients in an infant’s diet. 

What we also know however is that weight gain, or loss, is not only a result of how much we eat, which can be called our energy intake, it is also the balance between how much we eat, and how much energy we expend, which includes our physical activity.  The same must apply to infants!

It has been suggested that the physical activity of infants may also be determined by maternal factors including maternal BMI and physical activity, however this association needs to be interrogated more closely. 

Future research at the University of the Witwatersrand will provide us with South African data to understand what factors are associated with childhood obesity in our country, and whether we can intervene to reduce this risk.

Do you still think it is a good idea to fatten your baby up in the first year or two of life?

Dr Lisa Micklesfield is a researcher in the UCT/MRC Research Unit for Exercise Science and Sports Medicine based at the Sports Science Institute.  Her research focuses primarily on physical activity and body composition.

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