The practice of controlling the number of children particularly by means of contraception and voluntary sterilization.
Explanation:
Family planning is deciding the number and spacing of your children through the use of contraception such as natural planning and hormonal birth control.
Some family planning methods help prevent the transmission of HIV and other sexually transmitted infections. Family planning enables women to be healthier and pursue their education and career plus financial security.
the practice of controlling the number of children in a family and the intervals between their births, particularly by means of artificial contraception or voluntary sterilization.
From the context of the question, I am going to say placebo. This is me assuming, however, that both groups were told that their drinks had the protein powder
