Hunger signals are driven by a sensory perception based on what the food value is. This means that the total amount of food ate was already predicted before you actually ate it. These are dictated by neurons in the body that connect to the hypothalamus. Hunger signals are generated by the activation of AGRP neurons, which will induce a negative feeling and initiate food-seeking activities. We perceive a highly attractive food that generates a huge hunger signal, even if the food was replaced with not as attractive food the person will still overeat. Now, if nonattractive food was presented those hunger signals drop off, and if that was replaced with attractive food the amount of consumption would be profoundly less. This means that the foods we surround ourselves with make a huge difference in how much and what we eat.
In a recent study by Hall et al (2019), they compared processed foods to unprocessed foods and allowed the participants to eat as much as they wanted. What they found is that the participants who ate the processed food ate an excess of 500 calories more than the group who ate the unprocessed food. The unprocessed group increased body mass and body fat and ate food faster. The unprocessed food had an increase in PYY the satiety hormone and a decrease in ghrelin the hunger hormone. This relates to the above paragraph and how the brain and neurons can really dictate the amount of food eaten in a day.
This can also get magnified if sleep patterns are off, by messing up your circadian rhythms your body doesn’t get rid of cortisol like it is supposed to. As cortisol rises naturally throughout the day due to life stresses we need sleep to get rid of it so we can wake up feeling fresh the next day. A good way to check to make sure sleep is good and optimized is when you wake check your blood glucose and if it is elevated that will tell you cortisol is still high and you may not be ready to eat a carb-heavy meal or even eat a meal at all. It is not only important to get close to 8-9 hours of bedtime which will result in 6-8 hours of good sleep but when you get that sleep matters. It is in our DNA to wake up when the sun rises and that will signal to our body to start releasing dopamine which gets us moving and as the sun sets our body starts to release melatonin which helps release serotonin and can help us fall asleep faster and sleep longer. This natural cycle can be delayed by sleeping in too late, not being active in the sun throughout the day or at least some portion of the day, think a few 10-20min walks outside or staying up too late watch TV or being on your computer or phone. By messing up this rhythm your body doesn’t release as much leptin which is a hormone that tells the body we are full and well-fed and instead, it releases more ghrelin which is the hunger hormone that tells your body to keep eating and usually makes you crave foods that are highly palatable which as we discussed makes you tend to overeat.
References:
Hall KD, Ayuketah A, Brychta R, Cai H, Cassimatis T, Chen KY, Chung ST, Costa E, Courville A, Darcey V, Fletcher LA. Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell metabolism. 2019 May 16.