Carbohydrate-Insulin Model of Obesity

Overview

• The carbohydrate-insulin model of obesity theorizes that "diets high in carbohydrates are particularly fattening due to their propensity to elevate insulin secretion."
• The presence of high levels of insulin in blood may leads to the body absorbing too much glucose into cells. When the cells convert this excess glucose to fat for storage, weight gain sets in.
• According to this model, hormonal changes within the body promote calorie deposition in adipose tissue, exacerbate hunger, and lower energy expenditure resulting in obesity.
• The presence of insulin in the body is said to affect body weight because the hormone plays a major role in modulating the activities of several enzymes that are responsible for promoting uptake, retension, and storage of fat in adipose tissue.
• The above facts plus the fact that dietary carbohydrates are the primary drivers of insulin secretion in the body have led to the hypothesis that high carbohydrate diets are particularly fattening. 
• In summary, the carbohydrate-insulin model of obesity puts forth that "diets with a high proportion of carbohydrate elevate insulin secretion and thereby suppress the release of fatty acids from adipose tissue into the circulation and direct circulating fat toward adipose storage and away from oxidation by metabolically active tissues such as heart, muscle and liver."

Relationship Between Food Intake and Weight

• In carbohydrate-insulin model, the type of food intake i.e. carbohydrates is what results to weight gain as increased carbohydrates ingestion is believed to result in the elevated secretion of insulin, which in turn results in the convertion of blood sugar or glucose into fat for storage in the body's adipose tissue.
• Consequently, in this model, the intake of foods that are high in carbohydrates result in weight gain as a result of the activities of insulin in the body.

Arguements Against the Model

• A number of the logical consequences of the carbohydrate-insulin model of obesity have been investigated through carefully controlled inpatient feeding studies. The results of these studies failed to support key model predictions.
• Arguments against this model include the fact that high dietary fat can cause weight gain and obesity, usually at the expense of carbohydrates.
• The model is also considered by many researchers to be too simple in how it explains obesity and according to nutrition experts, "despite the popularity of low-carbohydrate diets, there are no long-term conclusive data to suggest these diets may increase metabolic function, suppress appetite, or lead to sustained weight loss."