What pregnant women eat and the diet of their new-born babies could be the key to defeating the looming obesity epidemic – and may even make children smarter.
You are what you eat. Or at least that’s what we’ve thought for centuries. But now, a growing mountain of evidence suggests your odds of being overweight or having diabetes later in life could be heavily influenced by what you ate during the first months of your life.
Indeed, it could be that your mother’s diet during pregnancy has set you on a path, which, although not irreversible, has a major bearing on your health and wellbeing.
It has long been accepted that our risk of obesity is a combination of our genes and our environment, but working out which genes and which environmental factors are most influential has been the subject of considerable scrutiny.
In spring 2013, the Wellcome Trust-funded UK10K project on rare genetic variants in health and disease produced a study (Genome-wide SNP and CNV analysis identifies common and low-frequency variants associated with severe early-onset obesity) that identified four new genetic variations linked with severe childhood obesity.
Dr Eleanor Wheeler, the lead author of the study, said: ‘We’ve known for a long time that changes to our genes can increase our risk of obesity. For example, the gene FTO has been unequivocally associated with body mass index, obesity and obesity-related traits.’
However, some researchers doubt that genes have much impact at all on our weight.
‘Recent analyses on the impact of genes on obesity and BMI (Body Mass Index) showed pretty disappointing results,’ said Professor Berthold Koletzko, from the Division of Metabolism and Nutrition at the Dr von Hauner Children’s Hospital, LMU Munich, Germany.
‘The cumulative effect of the 13 most potent obesity genes on variation of BMI was no more than 1 %. So that’s clearly not the answer to combating the obesity problem.’
While the scientists continue to battle it out over the impact of genes in child and adult obesity, few doctors would argue against encouraging their patients to eat more vegetables and do more exercise. All too often too few of us follow the advice for long enough to see sustained improvements.
Researchers are now turning their attention to a potentially easier target which could yield more powerful results: early nutrition. ‘What we have learned in recent years is that early nutrition and metabolism during pregnancy and shortly after birth have a very strong impact on the likelihood of subsequent obesity,’ said Prof. Koletzko.
‘What we have learned in recent years is that early nutrition and metabolism during pregnancy and shortly after birth have a very strong impact on the likelihood of subsequent obesity.’
Professor Berthold Koletzko, Division of Metabolism and Nutrition at the Dr. von Hauner Children’s Hospital, LMU Munich, Germany
For example, a recent study has shown that changes in diet and increases in physical activity during pregnancy can reduce the number of infants who are ‘large for gestational age’ by 30 % – a phenomenon sometimes known as Big Baby Syndrome.
These so-called Big Babies can have double the risk of obesity compared to a baby of average weight. Similarly, rapid weight gain during infancy is a sign of heightened obesity risk in adulthood, according to Prof. Koletzko, who has recently been awarded an Advanced Investigator Grant by the European Research Council (ERC) to investigate the metabolic mechanisms underlying these trends. His META-GROWTH project started in October 2013 and will run until the end of 2018.
His team is looking at ways to reduce the risk of obesity by understanding what kinds of foods consumed during pregnancy influence the likelihood of obesity in a child. For the moment, expectant mums are commonly recommended to eat plenty of lean meat, fish and folic-rich vegetables such as spinach and sprouts during their pregnancy to improve their baby’s long-term health.
Part of Koletzko’s work will be to focus on the study of nutrient transfer through the placenta as this is something which is not sufficiently well understood.
One theory to be explored is whether certain dietary factors could switch genes on or off at an early stage of foetal or neonatal development, producing lifelong effects.
By researching the role of fatty acids, glucose, and proteins on epigenetics – where environmental triggers influence genes – Prof. Koletzko wants to come up with guidelines for early nutrition.
‘Is it possible to change weight gain in infancy? We have shown that breastfeeding reduces weight gain by 15-20 %. And we have shown that by optimising infant formula through reducing the amount of protein, we can significantly reduce later obesity and obesity at school age.’
Windows of opportunity
Prof. Koletzko describes the first 1 000 days of life – including the nine months spent in the womb – as a ‘window of opportunity’ where the growth of babies is particularly sensitive to diet. ‘You can change course at any time in life but if you are already on a good trajectory it can make your life much easier. In terms of public health interventions, improving early nutrition can offer great benefit at a low cost.’
Identifying the precise stages in early life when children can be steered onto a healthier path is also the focus of the I Family project, a study that builds on an earlier project – IDEFICS – looking at the lifestyle and eating habits of over 16 000 children in eight countries. I Family catches up with these children as they move into adolescence, and also interviews their parents and siblings.
‘Early factors increase the risk of being overweight in infancy but there are opportunities to reverse this trajectory. So there must also be other factors affecting whether it persists or not. What we’re interested in are the transitions; how these children develop and what particular forces determine behaviour during these key periods – parents, siblings, peers, school,’ said Prof. Wolfgang Ahrens, Professor of Epidemiological Methods at the University of Bremen, Germany.
Innate food preference is also an issue. Just as some of us are genetically more likely to perceive strong bitter tastes, it may be that some children start life with a particular taste for sugary or fatty foods. Tests where children were offered juices and foods with or without added salt, fats, or sugars revealed that some children were more likely than others to make bad food choices. ‘Food preferences differ in that overweight children prefer foods with higher fat and sugar contents,’ explained Prof. Ahrens.
Another ingredient in the complex recipe leading to unhealthy children may be sleep deprivation. It turns out that people deprived of sleep have higher levels of insulin resistance than those who regularly sleep well. ‘Various regulatory circuits change if you are deprived of sleep. Insulin resistance increases after two days and growth hormone levels change, which has an impact on appetite.’
Being overweight during early childhood is reversible, and often rectifies itself naturally. The question is why this happens in some children and not others. And if input from schools, parents and peers can help, when is the best time to intervene?
‘Overall prevalence of being overweight increases dramatically around six years of age when children enter school. So some people say that this is an argument in favour of intervening around that period; I’m not entirely convinced about this but we need to look at it carefully – which is what we’ll be doing in the years ahead,’ said Prof. Ahrens.
The strong influence of early nutrition on our bodies is perhaps unsurprising. But could what we eat in our earliest days influence our mental performance later in life?
That’s the question Professor Cristina Campoy from the University of Granada, Spain, has been exploring as part of the EU-funded Nutrimenthe project.
‘We know that early nutrition – that’s prenatal and postnatal nutrition during the first two years of life – plays an important role in brain development and will exert a long-term effect which is detectable even beyond childhood,’ she explained.
Now, new imaging technologies like functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DFI) can show changes in how the brain works depending on early nutrition. ‘Diet during childhood seems to be central to improving mental performance in children,’ Prof. Campoy added.
She said that eating fish during pregnancy and having adequate levels of iodine and folic acid can have long-term positive consequences on brain development, as can the combination of nutrients available to newborns. ‘Folic acid nutritional status in the mother during pregnancy is essential not only to prevent neural tube defects, but also to avoid behaviour problems in the offspring during childhood.’
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