Obesity incidence has been rising rapidly, much too quickly to say it is caused by genetic changes. Clearly, the population's overall increased body weight from past years relates to overeating and diminished physical activity. However, a genetic overlay is likely, since not all who overeat become obese and relatively few people become morbidly obese. Morbidly obese patients undergoing bariatric surgery lose substantial amounts of weight, but despite severe restriction of food ingestion or the creation of significant nutrient malabsorption, they remain obese at their stabilized postoperative weight, their BMIs generally not falling below 35.
Livingston EH. Association of Morbid Obesity With FTO and INSIG2 Allelic Variants—Invited Critique. Arch Surg. 2008;143(3):241. doi:10.1001/archsurg.143.3.241