The etiology of obesity is far more complex than simply an imbalance between energy intake and energy output. Although this view allows easy conceptualization of the various mechanisms involved in the development of obesity, obesity is far more than simply the result of eating too much and/or exercising too little (see the energy-balance equation, below). Possible factors in the development of obesity include the following:

• Metabolic factors;
• Genetic factors;
• Level of activity;
• Endocrine factors;
• Race, sex, and age factors;
• Ethnic and cultural factors;
• Socioeconomic status;
• Dietary habits;
• Smoking cessation;
• Pregnancy and menopause;
• Psychological factors;
• History of gestational diabetes;
• Lactation history in mothers.