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New evidence why pregnant women do not need to ‘eat for two’

Study challenges theory of eating more during pregnancy

Adrian O'Dowd

Tuesday, 28 July 2015

The belief that pregnant women need to eat more to provide sustenance for their unborn child is unfounded, according to a study* published today in the journal eLife.

A study based on fruit-flies from the Medical Research Council’s (MRC) Clinical Sciences Centre (CSC) at Imperial College London, has suggested women may not need to “eat for two” during pregnancy because the body could adapt to absorb more energy from the same amount of food.

The researchers found a hormone is released during pregnancy which triggers the intestine to grow dramatically and stimulates the mother’s body to store more fat.

Irene Miguel-Aliaga, who is head of the CSC’s gut signalling and metabolism group, who led the research, said: “Previous studies have shown that eating for two during early pregnancy is unnecessary.

“Our research suggests that this is because the digestive system is already anticipating the demands that the growing baby will place upon our body.

“We normally think of our internal organs as being a fixed size, but the fact is that they are not. They can grow and change, and we show that this is important for making babies.”

The researchers carried out their experiments in fruit flies and said they were hopeful the results would translate to humans.

The study found what the authors called a “juvenile hormone” in the flies that triggered growth of the intestines soon after mating and which also stimulated fat storage.

This hormone acted similarly to human thyroid hormones that regulate humans’ energy demands within the body.

Jake Jacobson, also from the CSC and co-author of the study, said: “Many of the fly genes that we studied exist in humans, so our results are absolutely relevant. Flies also utilise and store fat like we do, and their metabolism is controlled by similar hormones.”

Dr Miguel-Aliaga added: “We know that in humans, the levels of several hormones change during pregnancy, and that these changes can affect how our digestive system works.

“We expect that these human hormones act in the same way that juvenile hormone does in flies, to resize the intestine and thus help the mother to extract more energy from her food.”

The research also suggested that, in people, if hormone levels failed to return to normal after birth, a mother’s intestine could remain abnormally large, so she would continue to extract extra energy from her food.

Dr Joe McNamara, head of population and systems medicine at the MRC, said: “This research points to a new scientific explanation why eating for two during pregnancy is not necessary, and may even be harmful, as a growing body of evidence indicates that a mother’s diet can impact a child’s propensity to be obese in later life. The important next step will be to reproduce these findings in humans.”

Dr David Richmond, president of the Royal College of Obstetricians and Gynaecologists (RCOG) said: “It is in fact a myth that you need extra calories for the first two-thirds of pregnancy. It is only in the last 12 weeks that women need an extra 200 calories a day.”

* Tobias Reiff, et al. Endocrine remodelling of the adult intestine sustains reproduction in Drosophila. eLife 2015;4:e06930. DOI: 10.7554/eLife.06930

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