Eating for two during pregnancy

Pregnancy is a wondrous and mysterious episode in life and, as such, it comes shrouded in myth. One of these pregnancy-related myths — the need to eat for two — has recently been debunked in a scientific study that reveals Mother Nature already has pregnancy nutrition covered. The study also suggests that giving in to the myth of eating for two might actually make it more difficult than expected to lose baby pounds after childbirth.

Dr. Irene Miguel-Aliaga led the study from the Gut Signalling and Metabolism Group at the Medical Research Council’s (MRC’s) Clinical Sciences Center at Imperial College London. The MRC international team of researchers based their study on previous research that indicated it is unnecessary to eat for two while pregnant.

The MRC researchers used fruit flies for their study because “Many of the fly genes that we studied exist in humans. Flies also utilize and store fat as we do, and their metabolism is controlled by similar hormones,” according to Dr. Jake Jacobson, a co-author of the study.

Juvenile Hormone Triggers Growth of Intestines

The study revealed that, shortly after mating, the female fruit fly’s body releases a hormone known as the juvenile hormone, which behaves in the fly much the same way thyroid hormones behave in the human body. Both regulate the body’s demand for energy.

In flies, activation of juvenile hormone causes the intestines to grow rapidly. This dramatic growth allows the body to absorb more energy (calories and nutrients) from the food the pregnant fly consumes. Juvenile hormones also trigger storage of added fat in the fly’s body cavity.

Digestive Changes Enhance Fertility

Changes in appetite were once thought to trigger the urge to eat for two but the current MRC research indicates the body physically adapts its ability to absorb extra energy almost from the moment of conception. In flies, this quick adaptability enhances fertility. When production of juvenile hormone was suppressed, female fruit flies produced fewer eggs than normal.

“Eating for Two is Not Necessary”

Dr. Joe McNamara was not a part of the study although he is Head of Population and Systems Medicine at MRC. About the study, McNamara said, ”Eating for two 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.”

Only 300 Calories per Day

Julie Redfern, a registered dietitian at Boston’s Brigham and Women’s Hospital, says nutrients are more important during pregnancy than added food volume or calories. She advises expectant mothers to add only about 300 calories per day to the diet during pregnancy. “One slice of whole grain bread and one tablespoon of peanut butter” is all that’s needed to add 300 calories to the diet.

The MRC research team speculates that the body’s natural ability to increase the size of the digestive system and to store extra fat during pregnancy may be reasons why so many mothers have difficulty losing weight gained during pregnancy.


  1. Reiff, Tobias, et al. "Endocrine remodeling of the adult intestine sustains reproduction in Drosophila." eLIFE. eLife Sciences Publications Ltd., 28 July 2015. Web. 12 Aug. 2015.
  2. "Nutrition and pregnancy: Scientists challenge 'eat for two' myth." MRC | Medical Research Council. Medical Research Council / Research Councils UK, 28 July 2015. Web. 12 Aug. 2015.
  3. Smith, Michael W. "If You're Pregnant, You Can Eat for Two, Right?" WebMD. WebMD, LLC, 1 July 2010. Web. 12 Aug. 2015.