|Image 1: Simplified illustration of the|
purported function of ghrelin in the
human body (healthhabits.ca)
For 14 days the scientists fed growing Wistar rats on either a 3x a day feeding schedule (three meals at fixed time points: at dark onset and at 3 and 6 h after dark onset) or ad libitum (rats had access to food whenever they were hungry). The hypothesis was that the scheduled feeding procedure would influence the rats' ghrelin levels and would thus affect food consumption and utilization. Yet, despite an anticipatory increase in acetylated ghrelin levels before 'feeding time', the rats on the imposed feeding-schedule did consume the exact same amount of calories as their ad libitum feed peers (note: when food was available the rats were allowed to eat to satiety). Notwithstanding, they did display "a slower growth rate compared to ad libitum fed controls", which would suggest that eating on a 3x a day schedule ain't the optimal feeding schedule to "grow" (muscle if you are an athlete, overall if you are still an adolescent or think of your children).
|Figure 1: Acetylated ghrelin levels in ad libitum (control) and scheduled fed rats (data adapted from Verbaeys. 2011)|
[...] scheduled-fed rats exhibiting a feeding pattern with intermittent fasting periods had a higher fat/lean ratio compared to ad libitum fed controls.In this context, it is particularly interesting that these effects are not attribuable to increased ghrelin levels, exclusively, as an additional ghrelin-treated control group did show a concomitant increase in both fat and lean mass (they were just bulkier), "but the fat/lean ratio was not significantly increased compared to controls".
|Figure 2: Body Composition Changes in ad libitum (control), scheduled-fed rats and rats that were injected with endogenous ghrelin (data adapted from Verbaeys. 2011)|
[these] results suggest that scheduled feeding, associated with intermittent fasting periods, even without a nutrient/calorie restriction on a daily basis, results in adipogenesis.In the above statement, the occurrence of the words "intermittent fasting" and "adipogenesis" within the same sentence, certainly is something Martin Berkhan from LeanGains.com won't like. In Berkhan's defense it has yet to be said that an "intermittent fast", as Berkhan proposes it in his leangains program, is somewhat different from the food-deprived periods between two feedings the rats in this study were exposed to. In a dieting scenario elevated corticosteroid levels, as they were observed in the scheduled fed group (cf. figure 2), are inevitable, anyhow (note: low-carb high protein diets are notorious for raising cortisol). And what most people forget: cortisol breaks down fat, as well. So after all, its not about eradicating corticosteroids all together, but rather about managing them.
|Figure 3: Glucose, triacylglycerol and corticosterone levels in rats after 14 days of ad libitum (control), scheduled feeding or ghrelin injection. (data adapted from Verbaeys. 2011)|
My assumption that higher cortisol levels and not elevated ghrelin levels (cf. figure 1) could be the main culprit, here, are corroborated by the results of a recent investigation into the role of baseline leptin and ghrelin levels on body weight and fat Mass changes after an energy-restricted diet intervention in obese women, which revealed that "[o]bese women with higher leptin and lower ghrelin levels at baseline seem to be more resistant to FM loss"(Labyen. 2011). It is also supported by a Finnish study (Cederberg. 2011) reporting that
An increase in UAG [unacetylated ghrelin] level during the exercise intervention [in 552 healthy young men (mean age 19.3 and range 19-28 years)] was associated with reduced weight, fat mass, fat %, and waist circumference, but not with fat-free mass. [...] Associations of changes in UAG level with waist circumference were significantly stronger than with fat % after the adjustment for confounding variables.Bottom line: Listen to the tummy rumbles, if you want to gain, ignore them and do some Yoga (or use other stress management techniques) if you want to lose weight, but by all means: Don't stress yourself, if you want to get/stay lean!