How food palatability effects hunger signals
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), palatability of processed foods was compared to unprocessed foods; participants were allowed to eat as much as they wanted of their assigned group. The study found that the participants who ate 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 dictate the amount of food eaten in a day.
This spike in ghrelin can also be magnified if sleep patterns are off. Disruption of Circadian rhythms prevents the body from getting rid of cortisol as it should. 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 ensure you’re getting optimal sleep is by checking your blood glucose in the morning. 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, too. 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. Then, as the sun sets our body starts to release melatonin, which helps release serotonin and can aid in getting to sleep faster and for longer. This natural cycle can be delayed in many ways:
1. Sleeping in too late,
2. Not being active in the sun throughout the day or at least some portion of the day (think a few 10-20 minute walks outside)
3. Staying up too late watch TV
4. Being on your computer or phone
By messing up this rhythm your body doesn’t release as much leptin (another satiety hormone) and instead releases more ghrelin, which usually makes you crave foods that are highly palatable, making you prone to overeating.
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.