hey MB, i read the first couple pages the other day and has some questions but forgot most of them lol.
what happens when the stead stream of nutrients stops, eg after 12hours of not eating?
i read about ghrelin, was increased ghrelin bad for fat loss/muscle gain or is increased levels good?
No problems Ener
Firstly, you would not be without a 'stream' of nutrients after not eating for 12 hours (Note I fast for 16 HOURS A DAY, EVERYDAY).
Simply put, 200 grams of Whey Protein (the fastest) digesting source of protein digests at 8-10 grams per hour (if taken with no other nutrients and made on water). So that would take a total of 20 hours to digest. When you add in the other macronutrients and whole food types (which digest at a much slower rate than Whey) of those macronutrients, the digestion speed slows down and down and down.
Now with fasting your metabolic rate doesn't drop until the 72 hours mark without food! And even then the down turn in metabolic speed is only 8%. So in real world situations, that is never something anyone needs to worry about. I'm not going to get into server long term calorie restriction as it does not apply either in 90% of the population.
Here is the best explanation (in layman's terms) - Ghrelin
Released primarily from the stomach, ghrelin goes to the brain where, predictable, there is a specific receptor. Among other functions, ghrelin raises levels of growth hormone. But that’s far from all.
Ghrelin also stimulates hunger (the only hormone so far found to do so) and appears to be a key hormone in initiating the hunger that goes along with meals; ghrelin drops prior to hunger and injection of ghrelin stimulates hunger specifically.
Even more interestingly, there is research suggesting that ghrelin levels become entrained to normal meal times.
So if you normally eat at 3pm (or whatever), you’ll likely find yourself becoming hungry at 3pm; this appears to occur from changes in ghrelin. I suspect this explains why people often have problems changing meal frequency, at least until ghrelin re-entrains itself to the new frequency.
That is, moving from a higher to lower frequency of meals is often accompanied by hunger at the previously ‘normal’ meal times. Moving from lower to higher is often accompanied by a lack of hunger until the body adjusts to the new frequency. I haven’t seen any work examining how long this takes but empirically it seems like it’s a couple of weeks or so.
Increased ghrelin also negatively impacts on pretty much all aspects of metabolism, slowing metabolism and increasing fat storage, at least it does this in rats with daily infusion.
In this vein, I’ve heard rumors that ghrelin is being promoted as a bulking aid for athletes and bodybuilders, both for the appetite increasing effects and the GH release. Given the negative aspects of ghrelin on metabolism, this is truly an awful idea unless the goal is to just get really fat.
In contrast, a ghrelin antagonist might be a very nice thing indeed for dieting. There appears to be work on orally available ghrelin antagonists going on.
As it turns out, ghrelin changes in the opposite direction of leptin; while leptin falls on a diet, ghrelin goes up. It almost goes without saying that leptin levels have a hand in controlling ghrelin; leptin appears to restrain both grhelin release from the gut and its stimulation of hunger.
So dieting, as usual is a double whammy in this regards: leptin goes down as ghrelin is going up with the reduction in leptin being partly responsible for the increase in ghrelin.
Ghrelin appears to play a role in both short- and long-term hunger and long-term bodyweight regulation. As mentioned above, ghrelin goes up prior to a meal; it also comes back down after eating.
However, ghrelin levels also increase overall with a loss of weight/bodyfat, decreasing when weight is gained. Individuals with a high BMI have lower ghrelin (and the idea of ghrelin resistance has been thrown around) and anorexics have higher ghrelin (which decreases with refeeding).
Nutritionally, carbohydrates appear to play a primary role in regulating ghrelin levels with dietary fat having less of an impact, the effect of protein is currently unclear. In one study, a high carbohydrate/low-fat diet generated weight loss without the normal increase in ghrelin levels.
And although only tested in anorexics, at least one study showed that the consumption of non-caloric fiber reduced ghrelin levels. Consuming small amounts of guar gum or psyllium fiber between meals might help to keep ghrelin down during a diet.
Perhaps ironically, it appears that low-sodium intakes increase ghrelin levels (although there is a racial effect). As I discussed in this article, I wonder if the low-sodium intakes taht contest bodybuilders and figure competitors often obsess about isn’t making things worse rather than better.
In one study increases in ghrelin with weight loss were related primarily to fat free mass loss but not body fat loss per se. As good reason as any to ensure that the diet is set up to prevent lean body mass loss.
Of some interest, one of the ways that bariatric surgery appears to be so successful is that, despite the massive weight loss generated, there is often no increase in ghrelin levels as would be seen with diet induced weight loss.
This may explain why weight is so rapidly lost, seemingly without hunger, with that surgery. I’d note that research also suggests that other hormone (such as Peptide YY, discussed next, and Glucagon like peptide 1, are more relevant to the hunger suppressing effect of the surgery).
For the rest of article that looks at all the hormones involved in fat loss have a read of this -
Bodyweight Regulation Wrap-Up: A Few More Hormones | BodyRecomposition - The Home of Lyle McDonald