The Fats role

They provide the remaining 30% of the energies of a Zone meal. According to the principles of Dr. Berry Sears' Zone Diet, it is a common belief that fats are the cause of fattening, and that therefore, by removing the fats, the weight loss process should magically begin. Now, I am not a doctor, therefore I limit myself to report some aspects reported by Barry Sears in his books (we suggest to read them to go in depth), but, in general, the principle on which the Zone diet is based on is avoid insulin swings. In fact, the Zone Diet is based on hormonal control obtained by putting Proteins and Carbohydrates (glucagon and insulin) in the right ratio. To maintain insulin in the Zone, the ratio between proteins and carbohydrates must be (at best) equal to 0.75. Fats do not affect the balance of regulatory hormones, but are essential for keeping the body in efficiency and for allowing fat-soluble vitamins to circulate and reach their destination, as well as slowing down the absorption of carbohydrates.
The fat classification is also shown below:

• Favorable: mainly fats obtained from vegetable foods (extra virgin olive oil or flax seeds) or fats derived from fish, rich in Omega3 (we recommend small-sized fish, such as sardines, rather than large ones, such as tuna and, therefore, fish that are at the bottom of the food chain, to reduce the intake of heavy metals such as mercury)
• Less favorable: fish at the top of the food chain
• Unfavorable: mainly fats from red meats, offal as well as saturated fats such as butter and lard, but also hydrogenated fats such as those contained in some margarines

Insulin and Glucagon: two key hormones!

Insulin is a hormone produced by the Pancreas and has the function of storing the nutrients inside the cells.
In fact, following the intake of a Food (or Meal) is caused an increase of the quantity of sugars in the blood, which however are kept under control through the secretion of Insulin which, in addition to conveying the nutrients inside the cells, is concerned with bringing the glucose level back to normal.
In case of assumption of a Meal composed mainly of Carbohydrates, this will most likely lead to what we have repeatedly referred to as Glycemic Swing , consequently triggering a high insulin response which, after having fulfilled the its tasks (bringing glucose back to normal and conveying nutrients inside the cells), will store excess calories, in the form of Fats, inside the cells. This is the reason why, according to Berry Sears, is the glycemic swings that cause an adipose storage inside the cells rather than the intake of Fats.
Glucagon is an Hormone as well and he is the antagonist of insulin and its role is to release the energy reserves stored in the cells. Diets low in carbohydrates and hyper-proteins act precisely on this principle, activating the process of ketosis. The Zone Diet has the objective of keeping these two hormones under control through the balanced intake of Carbohydrates, Proteins and Fats. The 40-30-30 balance avoids the Glycemic leaps, prevents the body from being invaded by Insulin and therefore prevent that the insulin will store excess fat inside the cells.