Study demonstrates that key role insulin plays in obesity | Dr Briffa's Blog:
The idea that obesity is a disorder of fatty accumulation (and not just down to the calorie principle) is explored in Gary Taubes’ book The Diet Delusion (titled Good Calories, Bad Calories in the USA). In this book, Taubes’ exposes the fallaciousness of the calorie principle, and instead goes after what might cause fatty accumulation in the body.
Now, fat is stored in fat cells as substances called triglycerides. Triglyceride is made from substances known as free fatty acids. It takes 3 fatty acids and one molecule of a substance known as glycerol to make triglyceride. The free fatty acids are absorbed from the bloodstream into the fat cells. They can flow out again too. What ‘fixes’ them in the fat cells is their conversion to triglycerides.
The conversion of free fatty acids to triglyceride is dependent on the supply of a substance called alpha glycerol phosphate. This is produced when glucose is metabolised in the cell. In other words, the more glucose that gets into the fat cells, the more fat will tend to get fixed there.
For most people glucose comes from sugars and starches (carbohydrates) in the diet. But to get into the cells it requires the action of the hormone insulin. So, dietary carbohydrate supplies the glucose necessary for the manufacture of triglycerides, and also stimulate the secretion of insulin which gets the sugar into the cells. Insulin also stimulates triglyceride formation through its action on other hormones (lipoprotein lipase, glycerol phosphate acyltransferase and hormone sensitive lipase).
In short, what this means is that carbohydrate and insulin will tend to cause the accumulation of fat in the cells.