When it comes to our nutritional appetite, the human body has innate mechanisms that regulate our satiety (hunger and fullness) signals. A substance that increases our appetite is said to be “orexigenic” and a substance that decreases our appetite is said to be “anorectic.” In response to the absence of food pushing against the gastrointestinal walls of our stomach and large and small intestines, a signal is sent to the Hypothalamus of our brains which triggers the release of Ghrelin, a gut hormone, Orexin and Neuropeptide P which increase our cravings for food. Once we have eaten and sugars and fats have been stored, juxtaposed gut hormones including Leptin, CCK, Adiponectin, GIP-1 and GLP-1 and PYY, signal we are full. For most, this gut instinct from gut hormones prescribes innately when and when not to eat and helps maintain a normal healthy body weight. However, food extremists have either stopped producing or become resistant to these signals, and so when it comes to eating, can no longer trust their gut feelings.
Hungry, full? Appetite? It’s all just gut instincts!Laura Campbell
Appetite is a natural instinctive desire to satisfy a need, in this case for food. It is a multi-faceted and highly regulated thing, with genetics, memories, diet, food availability, taste receptors and behavioural factors also playing a role. The human brain blueprint for appetite is dictated by our digestive system and gut hormones as part of the Gut-Brain-Axis. When we eat the presence of food in our gut causes distention (stretch) of the walls of the fundus, stomach and duodenum (parts of the gastro-intestinal tract that process our food in digestion). This triggers the colo-colonic reflex increasing motility in the tract and colon (pushing food through the gut). How fast food moves through the gut helps to regulate hunger with carbohydrates passing through fast, proteins slower and fats and some types of fibre the slowest (why you feel fuller for longer with a high fibre, protein or fat meal). Stress also slows gastric motility, but it also increases your desire for carbohydrates (so some people lose weight in stress and others gain, depending on if you respond by eating less due to slower gastric motility or by eating more carbohydrates). When we have eaten, Leptin hormone is made and released from fat tissue in response to fatty acids and glucose from carbohydrates from our food. Any food not directly utilised for energy, causes Insulin levels rise and GLP-1 and GIP-1 which help us store excess glucose as glycogen in the liver or in adipocytes (fat). Leptin, CCK, PYY, Oxyntomodulin and Insulin signal our brain to stop eating. What happens in anorexia is that the signals become dysregulated and so appetite becomes skewed and in obesity is that people become Insulin and Leptin resistant, making you more likely to binge eat.
What we eat also plays a major in appetite. Carbohydrates cause an “energy high” and then “low” and so a diet high in sugar is a recipe for binge eating as you feed your low energy with more food. Carbohydrates are however essential for the functioning of our body and brain, and without them we die. Alcohol is also a orexigenic (increases your appetite) stimulant and a diet high in fat and sugar triggers Dopamine the happiness hormone, to be released, hence the phrase “emotional eating” as people turn to food for emotional comfort. The more sugar you have the more you need to get the same effect. Just like at university when people say they “have a high alcohol tolerance,” the more sugar you have, the more you want as sugar blunts your response to sugar. It is also as addictive as cocaine. On the other side of the coin, Caffeine is an appetite suppressant, but have too much and you can’t sleep and the most major appetite inducer is a lack of sleep and rest as it vastly increases your desire for carbohydrates. Illness like colds or flu or infections or chronic illnesses, anything that drains you of energy also make you hungry, as they increase your desire for food to help you recover. Loneliness also plays a role in appetite, with a reduction in Oxytocin (the love hormone) inducing a desire for food. Eating a large portion also takes a lot of energy to digest (which is why you feel like a mid afternoon nap after a big lunch) which makes you more tired and so the more you eat, the more you hunger for more. Too much cardio exercise makes you hungry and too little does also. As a whole exercise reduces appetite and induces Endorphins, pain killer brain chemicals, which make you happier, giving you that “runners high” and so exercise is a good appetite suppressant. Your gut microbiota also plays a role, with a diverse gut microbiome helping to effectively regulate and manage gut hormones and gut inflammation and appetite. Consuming lots of prebiotics and probiotics, can help colonise a more varied biome and cultivate a healthier gut.
Food extremists cannot trust their gut instincts as they have an altered Brain-Gut-axis and so their gut instincts are making them ill. In recovery, anorexics must deliberately eat past their Leptin signals and deliberately binge in order to restore their body to health and those suffering from obesity must struggle with a constant Ghrelin and Leptin resistance insatiable appetite in order to get healthy. Both can feel wrong and both make you feel ill. However, once at a healthy weight, your gut does adjust and Leptin sensitivity returns, and you can learn to recognise and respond to natural body cues telling you when you are hungry and full. If these signals do not return, you must be aware of this and self-regulate, only giving your body what it needs. You must be your own gut instinct when your instincts are sending you astray. In recovery it is important that after your prescribed meals (varying based upon your body) you distract yourself with non-food related things from reading to working to tv to self-care, and get away from the kitchen unless you may be tempted to listen to your skewed gut instincts and deny yourself the health that recovery entails. Eat what you need to eat to get healthy and then get away from food. For a short time, trust your heart and not your gut and then when healthy, mindfully and intuitively listen to your gut as it will innately know what to do!
For food extremists you have to ignore your gut to get healthy and then when healthy befriend those gut instinct cues intuitively to stay healthy! Listen to your natural gut reaction! Feed and freeze food based on your gut impulses!
Copyright Laura Campbell 15/11/2020