Calorie balance certainly matters but it is not that simple. Most leading health research institutions believe dietary quality plays a major part in health and weight management. Certain foods are associated with patterns of overeating. https://www.hsph.harvard.edu/nutritionsource/best-diet-quali...

The average American diet has changed dramatically in the last century with the growth of the restaurant and food processing industry. Exercise participation has actually increased substantially in the last 20 years (https://www.cdc.gov/nchs/data/hus/2015/057.pdf) in the same time period obesity has soared.

Energy balance being responsible for weight gain is too readily used by the food processing industry in an effort to shift away blame for this epidemic.

A few instances: http://www.motherjones.com/politics/2015/12/obesity-exercise... http://www.cbsnews.com/news/good-news-pepsicos-indra-nooyi-s... http://blogs.plos.org/speakingofmedicine/2012/07/05/is-obesi... https://therussells.crossfit.com/2015/09/23/transparency-coc...