Obesity is a medical condition when a person or animal weighs too much and the excess weight is due to fat. Obesity increases the risk of heart disease, cancer, arthritis, and other illnesses. Obesity significantly shortens life expectancy. Some people who are obese are so because they have a medical condition that causes it, however, most just eat too much and/or don't exercise enough.
Irresponsible manufacturers sell food that is high in calories that tastes good but causes obesity and other health problems. If the law allows this they'll try and prevent their customers from knowing how fattening their products are. The Fast food industry is notorious for this.
There have been many documentaries covering obesity over the years. Several shows have also followed the lives of dangerously obese individuals. The TLC show, My 600-LB Life, stars a surgeon who performs life-saving operations on people who are considered "super obese."