Obesity is a multifaceted condition involving biological, developmental, environmental, behavioural, and genetic variables, and it is a major public health issue. The most prevalent cause of obesity in childhood and adolescence is an imbalance in energy balance, or an excess of calories consumed without an equal number of calories expended. Epigenetics, the gut microbiota, intrauterine and intergenerational impacts, and intrauterine and intergenerational effects have all recently been identified as contributing causes to the obesity pandemic. Other factors, such as being short for gestational age (SGA) at delivery, formula rather than breast feeding in infancy, and early protein introduction into an infant's diet, have been linked to weight growth that can last a lifetime. Childhood obesity is becoming more common, posing a substantial public health threat by increasing the burden of chronic noncommunicable diseases. Obese children and teenagers may also experience psychological problems such as depression, anxiety, low self-esteem, negative body image, peer interactions, and eating disorders.