Appetite Control: It’s Complicated

Too many people like to blame appetite problems on one hormone, or one macronutrient.  However, I don't think people appreciate just how complicated human appetite regulation really is.  From a recent review paper on the subject (with my highlights added in bold):

Appetite is regulated by a complex system of central and peripheral signals which interact in order to modulate the individual response to nutrient ingestion. Peripheral regulation includes satiety signals and adiposity signals, while central control is accomplished by several effectors, including the neuropeptidergic, monoaminergic and endocannabinoid systems. Satiety signals, including cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), originate from the gastrointestinal (GI) tract during a meal and, through the vagus nerve, reach the nucleus tractus solitarius (NTS) in the caudal brainstem. From NTS afferents fibers project to the arcuate nucleus (ARC), where satiety signals are integrated with adiposity signals, namely leptin and insulin, and with several hypothalamic and supra-hypothalamic inputs, thus creating a complex network of neural circuits which finally elaborate the individual response to a meal. As for the neuropeptidergic system, ARC neurons secrete orexigenic substances, such as neuropeptide Y (NPY) and agouti-related peptide (AGRP), and anorexigenic peptides such as pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART). Other brain areas involved in the control of food intake are located downstream the ARC: among these, the paraventricular nucleus (PVN), which produces anorexigenic peptides such as thyrotropin releasing hormone (TRH), corticotrophin releasing hormone (CRH) and oxytocin, the lateral hypothalamus (LHA) and perifornical area (PFA), secreting the orexigenic substances orexin-A (OXA) and melanin concentrating hormone (MCH). A great interest in endocannabinoids, important players in the regulation of food intake, has recently developed. In conclusion, the present work reviews the most recent insights into the complex and redundant molecular mechanisms regulating food intake, focusing on the most encouraging perspectives for the treatment of obesity.

Note how many hormones and other factors of your physiology are involved in regulating appetite.  And that's just the physiological factors.  Human psychology also plays a powerful role in appetite, and all of these physiological and psychological factors interact with each other every second of the day.  This is why scientists have not been able to develop a drug that can adequately tackle obesity, because if you develop a drug to block one pathway, another redundant pathway is there to take its place.  It's also why it is misguided for anyone to blame obesity on a single macronutrient, single hormone, or other single cause, and why there is no one-size-fits-all solution to permanent weight loss.

8 Responses to “Appetite Control: It’s Complicated

  • From that review paper, it makes it sound all-the-more ridiculous when people try and blame a single culprit. I struggle with figuring out the physiological/psychological continuum when it comes to appetite regulation. I think that while we are governed largely by hormonal/neurotransmitter influence – many people today just can’t discern between true “hunger” and “appetite”. In other words people tend to feed an “appetite” rather than satisfy a physiological “hunger”.

    • I also think there’s even more to the psychological component than differentiating hunger and appetite. There are studies showing things such as simply changing plate size, or social factors such as how much people are eating around you, will influence how much you eat. And that’s not to mention the research showing how psychological stress can affect appetite, with increases in appetite in some individuals but decreases in others.

      • Not to mention the fact that a good portion of our eating behaviour is pure habit, and bears no relation to appetite or hunger whatsoever.

        Just as a thought experiment, I wonder how long it would take an average person to significantly alter their eating patterns if someone surreptitiously managed to remove their appetite and hunger impulses. I don’t doubt that total food intake values would decrease, but I strongly suspect most people would keep sitting down for breakfast, lunch and dinner all the same !

        Or even better, suppose (again, a thought experiment) 100 average people not only had their appetite and hunger removed, but also (miraculously) had no need for any calories in order to survive. Now, here’s the kicker – how many of those people would ever even discover this miracle had occured?

        I suspect a good portion never would, as they would continue to eat according to social and cultural habituation.

        Cheers
        Harry

  • I think the psychology of appetite is definitely a real biggie. The way I’ve begun to be able to “control” my appetite in a sense is certainly very psychological. When I began to write down my food intake along with calorie and macronutrient intake so that I “know” I’m consuming what my body needs to acheive my body composition and fitness related goals hunger occurs with much less frequency and intensity. I can simply tell myself that there is no need to be hungry and it helps. This as opposed to the past where I consumed ample amounts of every macro (assumed due to sheer volume of consumption) and was still hungry all the time (offensive lineman). Then again as your article mentioned, so much is at play that by the time I “figure it out” some new pathway may be activated and I’ll need to start bulking in order to justify my new found insatiable hunger! Gotta love it.

  • A review by MR. Freedman et al. (Popular Diets: A Scientific Review, 2001) goes into detail discussing various physiological and psychological factors, and how they influence hunger and appetite.
    “Dietary compliance is likely a function of psychological issues…..rather than macronutrient composition, per se.”

    “Ogden notes that successful weight loss and maintenance may be predicted by an individuals’ belief system (e.g., that obesity is perceived as a problem that can be modified and if modification bring changes in the short-term that are valued by the individual concerned)”

    jhale

  • I know I’m not alone in having gotten obese through disordered eating behavior. IOW, feeding was by and large disjointed from appetite signalling. Obesity is, for a significant chunk of the population, an eating disorder. There is no physiological basis for not being able to have 2 cookies without devouring the entire box ten minutes later.

    I also believe that in the modern world, although it may not seem so, even the naturally thin will have to consciously “watch what they eat” from time to time. For example I’ve read that the Japanese indoctrinate the strategy of eating until 80% full. My thin friends may find their waistbands a tad snug after the holidays and this causes them to control eating a bit more for the next week or so.

    I think the most unreasonable expectation anyone embarking on a weight loss effort can have is to never be hungry. We are programmed so that chronic negative energy balance should provoke a person to eat. That’s why long term compliance and large losses are so difficult and rare no matter the diet composition. My experiences with low carb are that it worked for me for a very long time, but just listening to my hunger signals no longer works for further weight loss. After a while, even high protein has its limitations. Cruel as it may seem, the formerly obese have lower metabolisms on average than same weight never obese counterparts. So we never really get to “eat like a normal person”.

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