When I started as a PhD-student in the seventies, lack of high quality protein was considered to be the main nutritional problem world-wide and in my thesis I studied the quality of different protein sources. My focus was protein from whey, a byproduct from cheese manufacturing.
The protein content of whey is low but whey proteins are of high quality and have similarities with proteins in human milk. This stimulated me to study breast milk and later also the nutritional situation of women and children.
In particular I became interested in energy metabolism and body composition during pregnancy, lactation, infancy and childhood. A main reason was that new methodology for such studies had become available making it possible to study the requirements of dietary energy, to assess the amount of physical activity in human beings and also improving possibilities to assess nutritional status.
Together with my students, I have used these methods to study pregnant and lactating women, young children and infants, including those born prematurely. During later years our focus has been to apply such methods for identifying development of obesity during early life.