21 yo female, have always weighed 60kg during my teenage years, started dieting and now i am 45 kg, 164 cm, should i gain weight? my ideal weight 53

Puzzleing question: The data available in the US,from both body mass index and CDC growth standards show a young adult female at 164cm(64.5 in) to have a desired weight of 58kg and a healthy range of 53-62 kg.There are some obvious differences when comparing populations from different countries.By Us standards you would be considered underweight.see www.cdc.gov/growthcharts