|Image 2: 3D structural model of the IGF1 protein (rendered by Emw)|
From previous studies into the effects of exercise on IGF-1 levels activity, we already know that trained endurance athletes exhibit higher levels of IGFBP-1 (insulin like growth factor binding protein 1) than their sedentary counterparts (Manetta. 2003). Other studies have shown that after acute (vs. chronic) bouts of aerobic exercise the levels of IGFBP-1 return to baseline within 12-24h (Nindl. 2009; Berg. 2008; Koistinen. 1996) In that, the IGF-binding effect of exercise appears to be restricted to endurance type of exercises, as a more recent study by Nindl et al.found no increase in IGFBP-1 levels in young lean women after 8 weeks of strength training (Nindl. 2010).
|Image 2: Ronny Coleman's belly is recurrent topic on various bulletin boards. This image was part of a discussion on the muscular development forum. Is it s imply fat or the results of the false(?) belief in "the muscle building magic" of IGF-1? (photo by Dan Ray for MuscularDevelopment.com)|
[...] increased lean mass, aerobic fitness, and upper and lower body strength resulting from an 8-wk exercise training programs can occur without concomitant increases in either circulating bioactive or immunoreactive IGF-I, as well as associated IGFBPs. In terms of reflecting positive anabolic neuromuscular outcomes, these data do not support a role for endocrine-derived IGF-I. (Nindl. 2010)All horror stories about GH-guts aside, you may want to keep that in mind before you condemn all aerobic exercise as being anti-anabolic and pay a shitload of money for supplements that "have been shown in clinical trials" (why are you laughing? ;-) to increase IGF-1 levels.
|Figure 1: Effect of 6 month of aerobic exercise on serum free glucose, free insulin, HOMA-IR and IGFBP-1 levels in obese subjects (data calculated based on Prior. 2011).|
|Figure 2: Effect of high fat meal (84% fat, 13.7% carbohydrates, and 2.7% protein) on IGFBP-1 levels (data calculated based on Prior. 2011)|
[...] aerobic exercise training has a potentially beneficial effect to increase fasting plasma IGFBP-1 concentrations in previously sedentary middle-aged to older adults [..., a]erobic exercise training did not attenuate the adverse effect of a high-fat meal on plasma IGFBP-1 concentrations
It would be nice to see some scientists going beyond this illusive paradigm, in order to gain insights into the underlying mechanisms or, even more fundamentally, to answer the question whether high(er) levels of free IGF-1 are causative or just corollary to cardiovascular disease, cancer and all the other maladies IGF-1 is currently held responsible for and which role all the healthy low-fat grains we are supposed to eat play in the etiology of these diseases... in case that is going to happen within my life-time, you can be dead-certain (pun intended) that the SuppVersity is the place, where you will read about it first.