**Abstract**

Obesity is a complex disease that involves an excessive amount of body fat. It is a medical problem that increases the risk of other diseases, such as heart disease, diabetes, high blood pressure and certain cancers. Although there are genetic, behavioral, metabolic and hormonal influences on body weight, obesity occurs when you take in more calories than you burn through exercise and daily activities that is when energy intake exceeds energy expenditure. Diet plays an important role in the pathogenesis of obesity; fatty foods are energy dense and gives 9calories per gram compared to carbohydrate and protein that gives 4calories per gram. Also, if physical activity is inadequate, excess consumption of fat can results into weight gain. It does not take as much energy (about 3%), to convert and store dietary fat as it does to convert and store glucose. Fats are easily stored by the body. The aim of this chapter is to provide an understanding of physiological causes and effects of obesity as this will help to promote positive food choices. It is probable that an understanding of dietary patterns and how it relates to obesity will go a long way in the treatment of this complex problem.

**Keywords:** Food, Diet, Dietary Patterns, Obesity and Dietary fat
