Catchy headline, but does hold some truth. It's actually called malnourishment.
https://en.wikipedia.org/wiki/Malnutrition
In short, they do eat, but not the proper amount of quality foods and therefor missing-out on important part like vitamins and fibers (better known as macro nutrients).
Calories (which can be found all foods except water) is the amount of energy the food can potentially provide, but you still need these macro nutrients for proper functioning.
Many obese people lack these (macro) nutrients in there dietary habits and therefor develop all kinds of problems, like high cholesterol, skin problems, bone weakness, and diabetes.
Recently I found this doctors channel (yes, he is an actual doctor) which provides some really good information on this and many more subjects. https://www.youtube.com/c/DoctorMike