On the other hand, if the body takes in more calories than it burns, insulin will help to store those extra calories as fat. Again, it does not matter where the extra calories come from. In fact, if the extra calories are from carbohydrate, the body actually burns some calories in order to turn carbohydrate into fat for storage. In contrast, extra fat calories can be immediately stored as fat. To blame insulin as the sole contributor to obesity is not only ludicrous, it's irresponsible thinking.
Obesity is an extremely complex issue.
It has to do not only with excess calories and lack of exercise, but also genetics, psychological issues, social issues, medical problems and so many other things. The fact that normal portion sizes at restaurants are growing ever more outrageous, and that high calorie, high fat foods are cheaper and more accessible than ever doesn't help either. Obesity is not a simple issue and insulin is not the cause. For instance, in Japan, carbohydrates compose the overwhelming majority of daily caloric intake. High carb foods like grains, rice, and vegetables are daily staples of Japanese life, and intake of high protein, high fat animal products is minimal.