Nothing gets women more upset that being told 1) they are responsible for everything that goes wrong with their children 2) how much weight they should put on when they are pregnant (or rather they are putting on too much weight).

In what is simply another example of the ‘blame the mother’ theme, the release of the government’s new ‘not a plan’ plan for obesity prevention included guidelines for optimal weigh gain in pregnancy, some more loose talk about the role of pregnant women in how fat their children become, and this week a bit of coverage on a new study looking at, yes you guessed it, the role that pregnant women have in how fat their children become.

Part of the personal problem I have with the approach is having been pregnant myself (twice), something which I am pretty sure Jonathon Coleman has not been, is that I spent so much time vomiting up the contents of pretty much what felt like my entire body, I simply ate the few things I could keep down (mostly potato it turned out, oh and some other white food). Being told to eat a better diet, not put on so much weight (or put on more) by a bunch of male politicians and their male scientific advisors would have been like a red rag to a bull (I wanted to say something ruder but I am not pregnant so can’t use that as an excuse).

It turns out my feelings are not unusual, because there are quite a lot of quite angry women (and men) muttering about this very thing. They are angry no one has actually considered that pregnancy nausea is pretty prevalent. Rates of nausea in pregnancy may be as high as 90%, with half of women who have it experiencing moderate or severe symptoms and Pacific women being more prone to severe vomiting than others. As such what we eat during pregnancy is determined by more than just ‘personal choices’ or a ‘lack of knowledge about food and weight’.

Women are also peeved about being blamed for the obesity crisis, and they are ticked off that during a pretty body sensitive time (when most women’s bodies act in a seemingly totally independent) they are being told they are getting too fat. Awesome, thanks Minister and Ministry of Health.

But we at the Morgan Foundation are not about feelings, or opinions, no we are about evidence, and perhaps women (including me) just need to suck it up and be told what to eat and how much to weigh in pregnancy because we are in fact the solution to our obesity crisis?

Will the obesity crisis will be solved by ensuring women gain ‘the optimal amount’ of weight in pregnancy?

See that small speck of dust on your screen above this sentence? No, can’t see it? Well that then is a fairly accurate representation of our knowledge of whether intervening in weight gain and nutrition pregnancy will solve the obesity crisis.

What we do know about pregnancy weight gain and nutrition and obesity in children

The role of nutrition in pregnancy in our obesity crisis is one of the Prime Minsters Chief Science Advisor’s areas of research expertise, so no doubt this particular issue gets a fairly good airing in the halls of power whenever obesity prevention is discussed, hence it somewhat regular occurrence in the discussions. But the issue remains very unclear.

We do know there is a link between what we call “the inuterine nutritional environment” (so the micronutrients and chemicals derived from food that a developing baby is exposed to during its mothers’ pregnancy) and developing obesity in child and adulthood.

In very basic terms, the way foetal exposure is thought to work (remembering this is all just well informed theory) is that the nutrition a baby gets in the womb determines the way that a child’s appetite control and metabolism develops (setting their ability to feel full, their rate of growth and fat accumulation for example). If the nutrition is less than ideal then the baby will be more likely to gain weight as a child and adult. Importantly though for this weight gain to happen the child needs to be exposed to lots of easily available junk food – which we have today. That is why in the past the same kids had less chance of being overweight or obese.

We have also observed that women who are either overweight at the start of pregnancy, or gain more weight than recommended during pregnancy, are more likely to have either very large or very small babies; both are risk factors for disease in later life including obesity.

BUT it is quite difficult to measure in pregnant humans the precise chemical & nutritional environment a growing foetus is exposed to (most of the studies in this area are on animals). That is why in humans weight and weight gain is used as a proxy measure – a guesstimate in other words – for the nutrition the baby is getting. We assume that starting off a pregnancy in an overweight state or gaining more weight than is recommended is a good indicator of a poor nutritional environment for a foetus

As Nicola Hawley says (a Professor at Yale, who specializes in the foetal origins of obesity)

‘For a lot of these exposures we still have work to do to understand the underlying mechanisms by which obesity risk is transmitted to (a) child.’

Highlighting the work we still have to do to understand this theory is evidence that shows elevated levels of stress hormones during pregnancy also increase the risk of obesity in children. These are the same stress hormones that increase the risk for postnatal depression, and the same stress hormones we all experience during difficult life events (such as job insecurity or relationship difficulties).

We have no studies that have actually intervened in pregnancy weight gain and showed a result

So the relationship between pregnancy and obesity is a complicated one. And while the research certainly has potential and helps explain the intergenerational transfer of obesity, the fact remains there is no evidence on how to intervene in pregnancy weight gain and nutrition and whether that will even work to prevent obesity in the next generation.

It is like knowing that Dan Carter kicking the ball the wrong way in a world cup final will increase the chances of us losing (gasp!) but then concluding that we will base our entire winning world cup strategy on kicking training for Dan, while the rest of the team just loll around in five star hotels and drink Coca-Cola.

So, focusing on intervening in weight gain in pregnancy is certainly not going to solve the crisis that we are knee deep in right now. However, we do actually have a mountain of evidence about what will work.

Where SHOULD we focus our obesity prevention policy?

Last week we talked about some of the things we know that will work in dealing with the obesity crisis. The governments new ‘not a plan’ plan includes pretty much none of these things. As a recap here is what we know works to prevent obesity in the population at large (no pun intended)

Longer Exclusive Breast-Feeding
Comprehensive and Intensive School & Community Based Programmes
Tax on Junk Food and Sugary Drinks
Regulation of the Food Industry (e.g. nutrition labelling)
Prohibiting Junk Food Advertising to Children
Physical Environmental Changes (for example reduce the availability of junk food in schools and communities)

Note that intervening in the diets and weight of pregnant women does not make it on to this list. There is some evidence that lifestyle interventions may work in some circumstances work to prevent excessive weight gain in pregnancy but the evidence stops there because such interventions have little impact on other outcomes such as overly large babies.

Population wide approaches also reach pregnant women

If we are still concerned that we need to be doing something for women who are pregnant, we know that just like everyone else who is not pregnant, cost and convenience can predict unhealthy diets, therefore interventions that address the food environment and that we know work for the entire population are going to work for pregnant women too. In addition, given that 30-40% of pregnancies are unplanned targeting prenatal and early pregnancy nutrition is going to miss a significant number of women who don’t plan to, or even yet know they are pregnant – a problem universal approaches avoid.

Population wide approaches also have the benefit of avoiding stigmatisation. It sucks to be pregnant and then to be called fat (it kind of makes you not want to go public and do something about it). Any targeted programme for women at greater risk of unhealthy weight gain in pregnancy (in NZ this is Maori, Pacific and South East Asian women, those over 40, and those with a high BMI before pregnancy) further stigmatises women. Universal obesity prevention programmes will avoid this.

So Minister Coleman, in conclusion, stop hassling the pregnant ladies based on no evidence that it will work, and get on with the stuff that works to get us out of the proverbial mire and into a generation of healthier and more slim line New Zealanders.

 

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1) Jordan V, MacDonald J, Crichton S, et al. The incidence of hyperemesis gravidarum is increased among Pacific Islanders living in Wellington. N Z Med J 1995;108(1006):342-4.