Throughout history, science has invested enormous time and effort in the search to understand the physiological basis of obesity. Crucial to this research are the inquiry of how does our body control ingestion, digestion, absorption, and metabolism and how nutrients are distributed among various tissues, organs, and systems [1, 2]. Overweight and obesity, defined as body mass index (BMI, the weight in kilograms divided by the square of the height in meters) >25 and >30, respectively, are associated with premature death through increased risk of many chronic diseases, including type 2 diabetes, cardiovascular disease, and cancer [3–5]. Obesity is a major international public health threat and economic burden. Over the last 3 decades, the prevalence of overweight and obesity has increased rapidly. The latest World Health Organization estimates that 1.6 billion adults (aged 15 years and above) were overweight and 400 million were obese in 2005. These figures are predicted to rise to 2.3 billion overweight and over 700 million obese adults by 2015 [6].
