Obesity is a global epidemic and considered to be one of the most urgent public health problems of modern times. In adults, obesity rates have more than tripled since the mid 1970’s and for children obesity is now evident at birth and one in five people develop obesity prior to adulthood. Obesity is a disease with polygenic origins. Furthermore, exposures during critical periods of development invoke epigenetic alterations to cells and tissues with life-long effects to normal physiology. Conception and pregnancy are two periods of human development which are vulnerable to epigenetic modifications leading to future obesity risk. To break the intergenerational cycle of obesity, it is believed that interventions prior to conception improving gamete health and interventions during pregnancy influencing fetal growth will attenuate obesity risk of future generations. Until now these interventions have largely failed to improve offspring obesity risk for people. Studies are urgently needed to better understand the vulnerable periods for programming the ~50% unexplained variance in individual body size. Then we can develop and test interventions with greater specificity and implement public health strategies to overturn the intergenerational cycle of obesity. Until then, we must advocate for individuals suffering from obesity and bring attention to the necessity for more research.