|
Page 5 of 6
One last observation made in humans that is particularly beneficial is that high concentrations of IL6 cause a significant increase in calorie burning, especially fatty acid oxidation (burning fat for energy).7,8,21,23 Thus, it becomes clear that in active individuals, IL6 plays a beneficial role in energy production and accounts for some of the fat-loss effect seen with exercise (increased metabolic rate, increased fatty acid oxidation and increased release of stored fat from fat cells). However, in a sedentary person, the IL6 source is not active muscle but visceral fat, which causes insulin resistance to a disproportionate degree in the liver, resulting in the continuous release of excess amounts of sugar and higher insulin levels. This promotes fat storage over the long term, as is seen in type 2 diabetics.
Researchers have looked at experimental conditions in which IL6 is elevated. Some have exposed people to proteins found in bacteria that cause fever…others have injected synthetic IL6-like drugs. In both settings, fat loss is increased. Not only does muscle-derived IL6 have a net fat loss effect, but it also seems to aid in muscle growth. IL6 is a vital factor for the satellite cells to differentiate (mature) into myofibers, which is an early step in muscle hypertrophy (growth).24 However, this is only the case when IL6 is elevated in exercised muscle. Having systemically high IL6 levels, such as would be seen in obesity or during a fever, leads to muscle wasting. It has also been shown that natural testosterone levels are inversely related to chronic IL6 levels (meaning when testosterone is high, IL6 is low).25 Also, TNF increases with age, causing IL6 to increase as well, and higher levels of these two cytokines are associated with a higher risk of poor health or death.26 It remains to be seen what direction the field of research into cytokines will take, but one thing is clear amid all the confusion. Cytokines are not a simple set of hormones and the environment must be taken into account in order to understand their relative benefits and risks. It is possible that direct injections of IL6 into an exercised muscle or some method to upregulate IL6 production during exercise may increase the lipolytic effect of exercise, but there is no research yet to support that assumption. It is clear that chronically high levels of IL6, as opposed to acute elevations seen with exercise, are unhealthy and often reflect conditions that will lead to problems in the long run.
Nature did not intend for mankind to be sedentary and the duality of IL6 is a perfect example of a beneficial system that can cause problems in an unhealthy environment. Working the muscles intensely is a natural way to promote quicker fat loss and continuous muscle growth and IL6 appears to be one of the exercise-dependent factors responsible for many of the benefits of developing muscle mass and working out intensely.
So, is IL6 a friend or foe? The answer can be yes to both; IL6 is a friend to the fit and foe to the fat. Stay lean and work hard to keep this powerful hormone as an ally against obesity, aging and metabolic disease.8
|
Research and Review 
