Obesity is a major health concern for the U.S. but also in many countries around the world. There are many factors that may have influenced the rapid rise in obesity observed over the past 50 years. Among these are more sedentary and stressful lifestyles, larger portion sizes and more access to fast food. Also, higher consumption of sweetened beverages, especially by children and young adults, has been reported. All of these factors create an imbalance of energy leading to more calories consumed than expended which leads to gain in body fat. Other ideas about the causes of obesity have been proposed but have not confirmed. These include changes in gut microorganisms, viruses and contaminants in the water and air. There is no evidence to support a connection between GMO crops and obesity.
A connection between the use of genetically modified organisms (GMO) in the food system and obesity has been made by some people. The production of GMO grain, mostly corn and soybeans, in the US was about zero in the early 1990s and increased to 80-90% of the crop by 2010. During the same time period, obesity became more recognized as a major health concern and therefore it was easy to suggest a correlation between the two events. However, the obesity problem was well underway prior to the introduction of GMO crops in the U.S. Hence, the timing of GMO introduction and obesity rates do not suggest a relationship.
Another concern that has been raised between GMO crops and obesity is that as more corn was produced with better yields due to GMO traits, the availability of high fructose corn syrup increased. This led to lower costs for this sweetener, compared to sugar. It has been proposed that as more high fructose corn syrup was used by food manufacturers, this contributed to the obesity problem. There has been a substantial debate in the scientific community about the role of high fructose corn syrup in the obesity problem, and the general consensus is that high fructose corn syrup is equivalent to sugar in calorie load and is not more likely to cause obesity than any other form of caloric sweetener.
GMO technology is associated with more use of selected herbicides such as glyphosate (Roundup) which has also been suggested as a causative factor in obesity. Many studies have repeatedly found that glyphosate is not linked to health problems in the general population. Similarly, other traits used in GMO plants have been found to be safe for humans and animals to consume and there is no evidence that there is any connection to obesity or any other type of illness.