Why Am I Always Hungry?

Obese individuals often talk about having an insatiable appetite. Even when they are not hungry, they say that the first bites trigger their intense desire for food. They also experience prolonged feelings of unsatisfied hunger after eating. Hunger is a physiological mechanism in which the body signals that we need food supply. However, pathological impairment of this physiological alarm may lead to severe metabolic diseases. It seems that at least one of the mechanisms involved in the etiology of obesity is the disruption of appetite regulation in the bodies of obese individuals.

Feelings of satiety and appetite are precisely regulated by the complex interplay of the nervous and hormonal systems. The hypothalamus, limbic regions, and cerebral cortex are involved in regulating food cravings and feelings of fullness. However, the hypothalamus plays a primary role in regulating appetite.

Hormones such as insulin, leptin, ghrelin, glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and cholecystokinin (CCK) play a role in satiety and appetite control in coordination with the central nervous system. Ghrelin stimulates appetite, while PYY, PP, GLP-1, and oxyntomodulin inhibit appetite.

It has recently been shown that microbes residing in the gastrointestinal tract also play an important role in regulating appetite. They influence the energy balance and eating behaviors by impacting the gut-brain axis. Some microbial metabolites such as butyrate regulate hormones that control satiety. Some other products of gut microbiota such as neurotransmitters directly affect hypothalamus neurons. Imbalance of gut microbiome called dysbiosis, may lead to the impairment of normal satiety regulation and appetite-related disorders [1].

The hypothalamic control of appetite and satiety

The hypothalamus regulates hunger in coordination with gut hormonal mechanisms and gut microbiota. All appetite-related signals are integrated into the hypothalamus. The hypothalamus coordinates with the brainstem, higher cortical centers, and the limbic system. The hypothalamus receives numerous peripheral signals regarding adipose tissue stores and food intake, regulating metabolism and calorie intake.

Two important pathways that regulate food intake in the arcuate nucleus of the hypothalamus are the orexigenic neurons that stimulate appetite via neuropeptide Y/Agouti-related protein and anorexigenic neurons that inhibit hunger and promote satiety through pro-opiomelanocortin pro-hormone. These neurons signal to other hypothalamic nuclei and also reward systems in other parts of the central nervous system. Therefore, satiety and appetite are regulated through a complex interplay of various brain regions and gut hormones [2].

When individuals' gut senses that they consume more calories than their physiological requirements or excessive calories are stored as fat tissues, hormonal signals prompt the hypothalamus to activate anti-appetite mechanisms. However, in obesity, these mechanisms are disrupted.

Sugary and fatty foods impair normal mechanisms of appetite control in the brain

Eating for pleasure is the main cause of food cravings for high-sugar and high-fat foods. Despite feeling full, some people continue eating to satisfy themselves. Junk foods, full of sugar and fat and highly processed, seem to stimulate the dopaminergic reward system through signals from the hypothalamus or other parts of the brain. This system is also stimulated by cocaine and other drugs, and alcohol. Therefore, I believe food cravings should be considered an addiction. (Food addiction is not a diagnosis in the DSM-5.) This point of view alters traditional approaches to controlling food behaviors and managing obesity. According to this view, weight management should include drugs that target the brain's pathways and psychological approaches, in addition to lifestyle changes and calorie-restricted diets.

According to the “thrifty genes” theory, we have a genotype that conserves and stores more energy when food is plentiful. This was an evolutionary advantage for our ancestors who encountered harsh environments and food scarcity. They should possess a metabolic trait that allows them to consume higher-calorie food and effectively store it.

What can we do?

Transitioning to healthier dietary habits by eliminating junk food and reintroducing organic diets rich in vegetables, fruits, and high protein is the most effective strategy to curb insatiable appetite. Studies show that high-protein and high-fiber diets can elevate levels of anorexigenic hormones such as glucagon-like peptide-1, cholecystokinin, and peptide tyrosine-tyrosine, leading to a decrease in appetite. Simultaneously, these diets can lower levels of the orexigenic hormone ghrelin, which typically stimulates appetite. Moreover, proteins exert a higher diet-induced thermogenesis compared to carbohydrates and fats. During weight loss induced by dieting, the body reduces resting energy expenditure to compensate and keep energy. Despite weight loss, proteins help maintain resting energy expenditure without triggering hunger.

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Dietary fiber promotes anorexigenic mechanism through related hormones including GLP-1 and CCK. Moreover, soluble fiber as a substrate for the metabolic machinery of the gut microbiome, produces metabolites that influence the brain to control hunger and weight [3].

Psychological approaches may offer benefits in addressing hunger issues for obese individuals seeking weight management. Intuitive eating, which focuses on rational thinking and emotions to control appetite, is one of the best approaches. Group therapy also helps reduce hunger during weight management, similar to how it is successful in treating addictions [4]. Other techniques such as mindfulness have been widely used recently. Regular exercise, avoiding stress, consumption of enough water, and good quality sleep also help obese individuals manage their weight and hunger better.

If we disregard the new theory of the illusion of free will, it appears that there are some strategies to tackle the insatiable appetite in obese individuals, even when they have access to high-calorie and appetizing food.