There has long been controversy about what is driving the obesity endemic in our modern society.
This recent article , published in Nature Reviews, proposes Push and Pull Models of obesity.
In the Push Model, eating more calories than required drives weight gain. Here, (per the article), obesity is attributed largely to widespread availability of unhealthy, overportioned foods, and a sedentary lifestyle. High fat, high sugar foods stimulate the reward center in our brain to want more. (I would add that there are many other factors that can contribute that are likely more important, like genetics, hormones, medications that drive weight gain, gut bacteria (microbiome), poor sleep, health issues, learned ‘comfort eating’ from childhood, emotional drivers of eating, and so on.)
The Pull Model suggesting something different – namely, that having obesity results in eating to excess. In this model, hormonal factors favor deposition of calories into fat, leaving less energy available for other organs that need it. This perceived energy deficit results in hunger and increased food intake, and/or a decrease in metabolism/energy expenditure to conserve fuel. The types of food eaten are proposed to be the main influence here, with potential culprits including fructose and higher glycemic index carbohydrates. The Pull Model suggests that eating a lower glycemic index diet will be effective to help treat obesity.
In another recent article by Kevin Hall and colleagues, published in the American Journal of Clinical Nutrition, authors provide convincing evidence that the Push Model (aka Energy Balance Model) is where it’s at. They note many factors (such as those I have added to the Push Model above) which drive increased energy intake, and that simply reducing carbohydrate intake or eating lower glycemic index foods will not successfully manage obesity for the vast majority of people (the data clearly supports this).
BOTTOM LINE: Weight gain happens when calorie intake is greater than calories burned (it’s physics!). The data are solidly behind the Push Model, with many factors contributing to this positive calorie balance: many genetically driven, many outside of a person’s control. The exact contributors are unique to each individual, and are important to explore and identify, to optimize weight management success. (Learn about the ‘4M’ contributors to weight gain here!)
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