Foods that Contribute to Obesity
Part 2 - High Glycemic Foods
 Glycemic Index and Obesity
Foods that contain a high glycemic index are also likely to contribute to the development of obesity as they promote hyperinsulinemia and insulin resistance.
As insulin promotes lipogenesis an elevated level will produce alterations in carbohydrate metabolism and promote the storage of fat and in fact high glycemic index diets have been shown to stimulate lipogenesis and an increase in the size of adipocytes. Foods in which carbohydrate is digested more slowly have been associated with a greater potential to promote satiety.
Consumption of a low glycemic index meal has also been shown to affect the subsequent glycemic response of the following meal thus maintaining the beneficial effects on metabolism.
Conversely, foods with a high glycemic index produce a rapid increase in blood glucose levels which is often followed by a dramatic fall in blood glucose levels due to an excessive production of insulin and increased clearance of glucose from the bloodstream. This can then trigger food cravings and overeating in an attempt to restore blood glucose levels and in this way high glycemic foods may lead to an excessive energy intake.
Processed Foods Have a High Glycemic Index
Processed foods have been found to correlate with a high glycemic indexand as such this is one of the mechanisms in which these foods may contribute to obesity. Highly processed foods such as biscuits, desserts and other snack foods also generally contain significant amounts of fat and sugar added during processing which increases their energy density. In addition their high palatability is likely to be another mechanism by which over consumption of these foods may be promoted.
These foods are also generally low in fibre, which further influences the glycemic response. Foods high in soluble fibre produce a delay in gastric emptying and this subsequently may cause a reduction in the rate of glucose absorption and through this mechanism high fibre foods may promote satiety.
Fibre is also thought to reduce the availability of substrate for enzymatic breakdown by causing the formation of a viscous solution in the intestine. Due to these factors it is likely that foods that are highly refined and have been processed to remove their naturally occurring fibre, may contribute to obesity.
Examples of high glycaemic index foods include highly processed breakfast cereals ,white bread, wholemeal bread, potatoes, white and brown rice, confectionary, corn chips, gluten-free pasta, and commercially produced honey.
The probability of a diet containing a large proportion of high glycaemic index foods contributing to obesity will be greater for those with a genetic predisposition toward insulin resistance and a family history of diabetes, as their glycaemic and insulin responses are likely to more exaggerated than that of the general population.
High Glycemic Index and High Fat Foods Promote Weight Gain
Diets that contain a combination of high glycemic index and high fat foods are likely to be synergistic in promoting an increase in body fat levels in all individuals but especially in those with poor glycemic control and hyperinsulinemia.
The constantly elevated insulin levels inhibit fat oxidation and encourage the storage of fat in adipose tissue, such that fats present in the diet will be unable to be used by the body for the production of energy and will be effectively converted into fat stores.
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