GI Update

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Prof Jennie Brand-Miller answers your questions.


I am 30 weeks pregnant. I’m not eating for two. In fact I think I’m pretty much eating what I usually eat. So, how come I’ve gained all this weight?
It’s a very good question! Careful studies in well-nourished women reveal either no change in their food intake during their pregnancy, or only a minor increase that’s so small it simply can’t explain all extra energy (calories) deposited.

Scientists have long been puzzled as to why this is so. Some suspect that physical activity declines and others suspect that absorption of nutrients increases, but at the present time we really don’t know why most women do not appear to eat more during pregnancy yet gain weight.

In women from affluent countries like Australia, the average pregnancy weight gain is about 13 kg. Most is in the second and third trimesters and that’s a cracking pace in anyone’s books – half a kilogram every week for 26 weeks!

For a woman who gains the typical 12 to 13 kg (26 to 28 pounds), the baby weighs on average 3–4kg (6–9 pounds) at birth and the placenta 600g (1.3 pounds). The blood volume also increases, as does the weight of the uterus and breast tissue. Not surprisingly, the biggest variation is in the amount of fat a woman stores. It ranges from no increase at all in some developing countries to 5kg (11 pounds) or more in affluent countries. Here’s what it typically looks like.

Growth chart

But where does the weight come from? For average weight gain of 13 kg, a woman would need to eat around 75,000 calories of additional food energy over about 9 months. This is equivalent to roughly 275 calories (1125kJ) a day. But we know that mum’s appetite doesn’t change much and she’s not eating for two at all. In fact she’s pretty much eating what she usually eats (around 2000 calories/8400kJ a day on average).

A 2011 study in the European Journal of Clinical Nutrition which employed a smart little gadget called an IDEEA (Intelligent Device for Energy Expenditure and Physical Activity), helps shed some light on the subject. The study in 32 pregnant and 21 non-pregnant Swedish women, found that the decline in energy expenditure perfectly matched the increase in energy deposition required during pregnancy. But it was a very subtle difference. The pregnant women simply slowed down; they lay down a little longer, they stood less; they walked or jogged or trained at a slower pace – but it amounted to about 225 calories (945kJ) less per day.

To me, these findings have important implications for the slow incremental weight creep that generally accompanies ageing, in both humans and animals. As we gain weight, we don’t necessarily eat more….we just move less. That’s not so surprising because just like pregnancy, a heavier body can be a little awkward and take more effort to lift. In fact, the mathematicians have worked out that our current obesity epidemic can be explained by just 7 excess calories a day over and above our energy needs. In other words that extra bite of apple was your undoing!. Seriously, no one, even a dietitian, can fine-tune calorie intake and calorie output to that fine degree.

The lesson from pregnancy is that obesity is not a disease of gluttony and sloth as so often portrayed, but one where just the smallest effort (the decision to use the stairs instead of the lift, or eat one mouthful less at dinner), has a ripple effect on your whole life.

Prof Jennie Brand-Miller and colleagues Dr Kate Marsh and Prof Robert Moses have just published a book called The Bump to Baby Diet – a low GI eating plan for conception, pregnancy and beyond to share the latest science and help women enjoy a healthy pregnancy while safeguarding their baby’s future wellbeing. It’s available from bookshops and online in Australia and NZ and as an eBook from Amazon, iTunes etc. You can look inside HERE.

New GI values from SUGiRS.
Cooking with Carisma.
Back in 2006 we sat down with chef and potato expert Graham Liney, Australian potato growers and the Dutch potato breeding company Agrico, to bring Carisma, Australia’s first low GI potato to your table. It’s a versatile, general purpose potato that’s full of flavour with a creamy taste and ‘melt in the mouth’ texture. When boiled (skin on) and served slightly al dente it has a GI of 55. We are now delighted to let readers know that Carisma fries and Carisma mash also have low GI values.

  • Carisma fries (cooked in olive oil using a Tefal Actifry): GI 53
  • Carisma mash (boiled then mashed with olive oil): GI48

A standard 150g (6oz) serving of fries or mash provides 15g carbohydrate and has a glycemic load of 8.

GI testing by an accredited laboratory
North America
GI Labs
Dr Alexandra Jenkins
Glycemic Index Laboratories
20 Victoria Street, Suite 300
Toronto, Ontario M5C 298 Canada
Phone +1 416 861 0506

Fiona Atkinson
Research Manager, Sydney University Glycemic Index Research Service
Human Nutrition Unit, School of Molecular and Microbial Biosciences
Sydney University
NSW 2006 Australia
Phone + 61 2 9351 6018
Fax: + 61 2 9351 6022