Portion sizes are larger. Low fat products are everywhere, and many people believe that low fat is healthy and therefore can be consumed freely without regard to quantity. Many Americans ignore calories and fail to get enough exercise. Another possible cause for the increase in obesity is Americans' obsession with fat in the diet and attempting to eliminate or reduce it by overeating low fat foods. However, many low-fat foods are actually higher in calories than regular fat versions.
Physical activity counts too.
Nearly a third of Americans don't get enough physical activity. Instead we spend too much time sitting at our computers, driving the car, watching television, and taking the elevator instead of the stairs. By sticking with the basics, weight loss and maintenance can be achieved by adding a few simple changes to your lifestyle. There is no quick fix. BMI is a measure that relates weight to height and correlates with body fat.