Why We Cannot Spot Reduce

by : Roger Grant

Fats are stored as triglycerides in our fat cells and have to be broken down and transported via the blood to get anywhere else. They cannot just jump directly across into the nearest exercising muscle to be burned. If fats are going to be burned in the muscles, then the following events must occur:

1. Triglycerides in the fat cells become hydrolyzed and break apart releasing the fatty acids and the glycerol molecule into the blood.

2. The fatty acids travel via the blood in the veins throughout much of the systemic circulatory system where they eventually reach the heart.

3. They then travel in the blood to the lungs where the blood gets oxygenated and then travel back to the heart.

4. The fatty acids then travel via the blood in the arteries where they eventually reach the mitochondria of the muscles.

5. The fatty acids are then activated in the mitochondrial matrix after which they are oxidized to release their energy in the Krebs cycle.

The proximity of the fat cells to the muscles does not affect the necessity of this process in any way. As a result, there is no advantage for the body in selecting fats from cells based solely on their proximity to muscles that are being used, and no reason to do so.

Another case where fat is burned is in the case where energy is needed to convert lactic acid back into glucose. This conversion back to glucose happens due to a process called gluconeogenesis via the cori cycle in the liver and the accumulation of lactic acid results from anaerobic glycolysis due to bouts of relatively intense exercise (such as training abs until you feel them "burn"). This lactic acid travels from the muscles to the liver via the blood, and converting it back to glucose requires energy input which is supplied by fats (as mentioned in another article). Just like in the previous case, the fats have to travel throughout much of the systemic and all of the pulmonary circulatory system before they can be used for energy in the liver. Also, there is again no reason why fats should be selected based on the location of the fat cells in which they originated.

Another argument against the spot reduction myth is that the body uses hormones (such as epinephrine) to catalyze the mobilization of fats. These hormones exist in liquid form and are transported via the blood. The blood containing these hormones will be pumped throughout the entire body and there is no reason why it should go to some fat cells but not others. Any difference in fat mobilization is due to the difference in sensitivity of the fat cells to the hormones. Again, there is no reason why the fat cells should change their sensitivity based on what muscle is/was being exercised.

Whenever we examine the process of fat burning, the facts present clear and compelling evidence against any notion of spot reduction or selective fat burning. Clever marketing notwithstanding, spot reduction has no basis in science. It is misinformation that is propagated and exploited for the monetary gain of some at the expense of others. The closest that we can get to spot reduction, is to employ surgical methods such as liposuction.