Obesity has already reached epidemic proportions, affecting an estimated 300 million people worldwide. It occurs as a result of genetic, behavioral, environmental and physiological factors, which cause energy imbalance and promote excessive fat deposition. Although genes play an important role, behavioral and environmental factors (i.e. sedentary lifestyle combined with excess energy intake) have been reported as fatal causes for the dramatic increase in obesity during past twenty years. This study is conducted among patients with an excessive body weight, which showed that the potential cause of weight gain among overweight and obese people could be consumption of a diet with a high glycemic index and glycemic load. Another reason might be relatively low intake of dietary fiber and low level of physical activity. There is increasing evidence that a low glycemic index/load diets are effective in weight control and treatment of obesity. The study suggests that there is a need to change eating habits and current lifestyles of people with an excessive body weight. This can be an important step towards combating the obesity epidemic.