[user104658]

Obesity (childhood and otherwise) is caused by over-eating and lack of physical activity. Full stop. Cutting sugary drinks / fatty foods specifically will do absolutely nothing if a child is still overfilling on carbs at dinner time and not burning them off. It's really as simple as that.

There are a myriad of OTHER reasons to try to improve the quality of food our kids eat; overall nutrition and avoiding deficiencies. You can tell which kids eat well because they have healthy hair, healthy skin, more energy. Whether they're slim / fat is purely down to quantity and activity.

Basically... there are a LOT of unhealthy kids out there eating nothing but junk food, with nutrient and vitamin deficiencies, bad skin, dull eyes, lethargic... and stick thin.