Insulin, Fat and Protein

There is a tendency to focus on carbohydrates when discussing topics like diabetes and nutrition, as if they are the only nutrient of real concern. However, fat and protein are also important to diabetes. When insulin fails to perform properly due to fat metabolism, diabetic complications can develop. This is particularly pertinent in the case of type 2 diabetes (T2D). In this form of diabetes, it is common for fatty substances to obstruct and destroy the arteries leading to high rates of cardiovascular disease.

Actions of Insulin concerning Fat

Insulin works in the body by performing several tasks. Among them are the following:

  • Sparing fat – Fat is the substance the body holds in reserve for energy. Glucose, on the other hand, is for immediate release to meet energy needs. Insulin, by assisting the entry of glucose into the cells of both the liver and muscles, decreases the potential demand on fat cells. It allows the fat cells to continue storing energy for later use rather than fulfilling the immediate energy requirements of the body.
  • The promotion of fat synthesis and storage – The liver is capable of storing excess glucose. However, storage capability is finite. As a result, the liver needs to find an alternative means of dealing with any extra glucose that cannot be turned into glycogen. Insulin helps to convert the glut of glucose into fatty acids. It is then transported in the blood stream as lipoprotein.
  • Reversing the process – Insulin performs a catalyst role by acting upon another hormone – lipoprotein lipase. The catalytic role puts into motion the actions of lipoprotein lipase as a means of reversing the liver process which resulted in the creating of the lipoprotein. It acts in the capillaries of the liver tissues to break down the lipoprotein so the fatty acids can build up in the adipocytes (fat cells) of the adipose (fat) tissues.
  • Inhibiting the reversal within fatty cells – Insulin can also inhibit the changing back of lipoproteins within the fatty cells. This prevents the fatty cells from escaping into open circulation, keeping them confined to the adipose tissue.
  •  Glucose production – Insulin helps glucose penetrate fat cells. In doing so it helps the merger of fatty acids and glucose to form glycerol.

Fat and Insulin – When Insulin is Lacking

When insulin is lacking, very little goes according to the expected pattern. Other processes begin to make up for the lack of insulin. For instance, any triglycerides (fats) being stored are freed and begin to circulate in the blood. They become the supply of energy for the body’s cells. The only exception is the neuron cells of the brain since they are unable to use triglycerides. The release of fats results in the build-up of cholesterol in the blood. This, in turn, can lead to arterial degeneration.

Another problem emerges as the cells try to satisfy their energy requirements by using fatty acids. An interruption of the normal metabolic cycle occurs. There is an excess of ketones (usually acetone) created which creates a change in the pH of the blood.[1]  Diabetic ketoacidosis develops which is a medical condition in which blood and body tissue acidity rises. The acetone smelling breath of an individual who is diabetic is a symptom of the condition, as the body uses heavy breathing in an attempt to correct acidosis by blowing off carbon dioxide. If the problem is not addressed and corrected, it can lead to a coma followed by death.[2]

Fat Cell as an Endocrine Organ

Adipose tissue manufactures proteins that perform as paracrines (substances that act upon cells nearby to the one that releases them) that operate locally.[3] Yet these proteins are also comparable to an endocrine hormone. In this role, the proteins circulate all over the body and influence both feeding activities and insulin behavior. An example of this type of protein is leptin. It is produced within the adipose tissue and acting on the brain, affects the feeding behavior. The autonomic nervous system adjusts its production.[4]

Insulin and Protein Metabolism

Following a meal there is a surplus of food nutrients in circulation. Insulin acts upon them in several ways. In doing so, its actions extend to several substances.[5]  These substances include:

  • Amino  acids
  • Carbohydrates
  •  Fats

Amino acids are the chemical building blocks that make up proteins. Insulin plays several roles in the formation and delivery of proteins. It does this initially by working with the growth hormone to help amino acids pass through cell walls and into the cell interiors as part of an active transport mechanism. Insulin also encourages the development of protein and prevents protein destruction in metabolism. It also plays a part in the formation of new proteins that are constructed from those amino acids that insulin has helped to gain cell entry. Without the presence of insulin, these processes could not occur.5

Insulin also plays a role in other significant aspects of protein development and usage. Consider its effect on the amino acids in the liver. Once amino acids gain entry into the liver through the blood, it may convert them into glucose. Insulin inhibits this particular action. In doing so, it performs the actions of a protein sparing mechanism.

Yet, sometimes, insulin is most noted when it does not perform. When insulin does not go into action or perform any of the above tasks, the following actions occur:

  • Protein is broken down
  • Its  amino acid constituents appear in the blood in excess
  • The amino acids are used wastefully for energy
  • They are then excreted in the urine


While carbohydrates often seem to be a main topic, it is a mistake to ignore the significance of fats and proteins. Their relationship to insulin is of major importance to diabetics.


[1] Marcovitch, H (2006). Black’s Medical Dictionary 41st edition. Lantham, Maryland: Scarecrow Press.

[2] Guthrie, DW; and Guthrie, RA (2003). The Diabetes Source Book. New York: McGraw Hill; and Meltzer, SJ; and Belton, AB (2009). Diabetes in Adults. Toronto: Key Porter Books

[3] Walker, S and McMahon, D (2008). Biochemistry DeMYSTiFieD. New York: McGraw Hill.

[4] Murray, R.K;  Bender, DA; Botham, KM; Kennelly, PJ; Rodwell, VW; and Weil, PA (2009). Harper’s Illustrated Biochemistry 28th ed. New York: Lange McGraw Hill.

[5] Guyton, AC; and Hall, JE (2011). Textbook of Medical Physiology, 12th ed. Philadelphia: Saunders.

This article was originally published July 12, 2012 and last revision and update of it was 9/10/2015.