Even without being pregnant, each of us is always eating for two, because we also have to feed our own intestinal microbiome, which receives and metabolizes about 30 percent of our ingested nutrients. If the nutrients didn't enter our bloodstream, did we really get them?
Leann Birch at Penn State University asked a group of eleven-year-old girls what they ate, and videotaped them while they ate it. She then divided up the group into weight tertiles -thin, normal weight, overweight- and showed that the thin and normal weight kids reported correctly, while the overweight kids underestimated the candy, soda, and desserts that they ate -except for one item. They reported their juice intake correctly because they thought juice was healthy.
Most of the data in nutritional studies are obtained through memory recall to food questionnaires. You can see for yourself -try asking someone what they've eaten for the last three days. Most people can't tell you what they've eaten in the last three hours.
Nutritional mythology has never been more fervent than it is now, in part because life span and health span declining -everyone wants to blame someone, or something, including me.