There is significant consensus in the scientific community that environmental factors, especially the easy availability of highly processed foods and sedentary lifestyles, have contributed to increasing obesity rates.
However, there is much disagreement about how these environmental factors contribute to weight gain.
According to the predominant energy balance model (EBM), consuming more calories than those burned results in a positive energy balance and weight gain.
The increased caloric intake due to the easy accessibility of highly palatable and inexpensive processed food and lower energy expenditure due to reduced physical activity levels have contributed to the global increase in obesity.
In other words, the EBM suggests that successful weight loss requires reducing total calorie intake. This involves consuming fewer calories and increasing physical activity levels.
Unlike the EBM, the carbohydrate-insulin model (CIM) posits that the quality of food consumed plays a critical role in body weight management rather than total calorie intake.
Specifically, consumption of processed and starchy carbohydrates that cause a rapid increase in blood glucose levels results in their storage as fat. Increased fat accumulation sets off a feedback loop resulting in increased hunger and possible consumption of calorie-rich foods.
The CIM states that it is the increase in fat storage due to the consumption of processed carbohydrates and not increased calorie intake that leads to weight gain and is primarily responsible for elevated obesity rates.
A recent article published in the American Journal of Clinical Nutrition provides a comprehensive description of the CIM, along with testable hypotheses that may help clarify the precise changes in nutrition necessary to lose weight or maintain a healthy weight.
The article’s first author Dr. David Ludwig, told Medical News Today, “If the CIM is right, then the conventional approach to weight loss, the low-calorie diet, is likely to fail for most people over the long term. We argue that people have more control over what they eat than how much. A focus on reducing processed carbohydrates, rather than calorie restriction, may be more effective by lowering the biological drive to store excessive fat.”
Flaws of the EBM
According to the EBM, a positive energy balance where a person takes in more calories than they burn is primarily responsible for weight gain. In other words, the EBM regards all calories in the same way, regardless of their dietary source.
The proponents of the CIM acknowledge that a positive energy balance is associated with weight gain, but this does not establish causation.
They argue that metabolic and hormonal changes that occur in response to the consumption of specific foods are the root cause of weight gain, with excessive calorie intake being the outcome.
Although calorie intake tends to increase during puberty, some experts think that it is the biological changes rather than positive energy balance that is responsible for the growth spurt.
Therefore, while the EBM focuses on the overall consumption of calories, it ignores the role of food quality and the subsequent metabolic processes and hormonal changes in mediating weight gain.
Moreover, reducing caloric intake tends to be successful as a weight-loss strategy only in the short term. This is due to the body adapting to the lower calorie intake, resulting in lower metabolic rate and increased hunger.