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Originally posted by Dr. Pain Gives new meaning to HOMEOSTASIS!  Yes Thanks TCD.......if I get time today, I will post some night-time saiety tricks! DP |
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I'm basing my comments on a few observations. 1. CCK (cholecystokinin, a rather potent hunger supression factor) only works when leptin is present in high enough concentrations. When leptin is low, CCK doesn't blunt hunger. 2. Leptin appears to 'win' the battle over ghrelin in the NPY/AGRP neurons (the main ones that stimulate hunger/slow metabolic rate). That is, when leptin is low (for example, early in the day), ghrelin will reliably stimulate hunger and eating. When leptin is higher (at night), ghrelin has no effect. 3. Simply thinking about the purposes of the various hormones. Leptin is primarily a marker of overall body energy stores (and to a lesser degree short term caloric balance over a day's span): bodyfat mass. It's relatively slow changes (at least 5 hours to change after meal, to days) is an indicator of this. Ghrelin/insulin and all of the others (the dozen and one gut hormones like GLP, CCK, etc, etc) are mainly markers of short term (meal to meal) energy balance. They change in seconds (insulin) to minutes or a couple of hours (the others). The amount of bodyfat/stored energy is a crucial controller of overall survival, far moreso than any individual meal. So consider a couple of situations. When leptin is high (bodyfat mass is sufficient, overall calorie balance is sufficient), you still need to eat to supply the body with energy and nutrients. So the other hormones (ghrelin, insulin, CCK, etc) are still going to do their jobs. Ghrelin will stimulate hunger and the other hormones will shut it off when you've eaten enough (assuing no other defect in the system). So during the day, when leptin is relatively lower (and I suspect sensitivity to the other hormones higher), you'll get hungry when you need to eat, and get full when you've eaten enough. You're simply fulfilling short-term energy needs. At night, when leptin is higher and it's time to sleep, the other signals won't really affect hunger. You should be sleeping, not foraging for food. But when leptin is low (low bodyfat, starving to death or b/c you're dieting), all that matters is restoring energy stores. Individual meals take a far secondary role in the overall scheme, what matters is restoring bodyfat mass to a safe level (just in case the next famine comes along). So it makes sense that the short term hunger blunting hormones (CCK and the rest) wouldn't have an impact on stopping a meal. You need to cram every calorie in that you have available. It makes more sense that ghrelin would have a larger impact as well, making you hungrier that much more. You also tend to have trouble sleeping although that's probably more a cortisol/catecholamine issue. So basically, leptin would appear to be determining how well (or poorly) the other hormones work at doing their job in the overall scheme. And this is empirically true. Once you get very lean (low leptin), even if you do everything 'right' in terms of meal planning (high fiber, moderate fat, all that crap to slow gastric empthying), none of it matters. You still don't stay full for very long and get hungry again pretty soon. Why? Becuase the low leptin is setting hte overall 'tone' of the system; none of the short-term satiety factors can do their jobs very well. High leptin (or normal leptin) means you've got enough bodyfat, your body simply needs to worry about short-term energy needs. So all of the other sytems (again, assuming no other defect) work just fine. Low leptin (and maybe leptin resistance since the end result is more or less the same) makes your brain think you're starving, short-term energy needs are no longer the most critical aspect: restoring fat mass to a 'safe' level is. So you shouldn't get full very readily, if the food is available, you should be eating as much of it as possible to restore fat mass. And that's why dieting sucks. Lyle |
*prints out leptin articles*
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Originally posted by Dr. Pain Gives new meaning to HOMEOSTASIS! Yes Thanks TCD.......if I get time today, I will post some night-time saiety tricks! DP |
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Originally posted by Yanick Lyle has a great way to keep us optimistic about dieting
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His info isn't all to encouraging though, as he likes to talk about the fact that we don't really have control over our appetites and that we're pretty much f*cked in terms of dieting.
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Originally posted by The_Chicken_Daddy This really suprises me. You seem like the kind of person who enjoys hunger pains and cravings so you can battle them and build character. You seem like the kind of person who would purposely get hooked on heroin just to go cold turkey. |
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Originally posted by mama's boy Am I the only person here who likes being hungry? |
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Originally posted by mama's boy Am I the only person here who likes being hungry? |
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