Not All Hunger Is Real Hunger: Understanding the 3 Types That Control Your Cravings

Hunger isn’t just a rumbling stomach—it’s a sophisticated survival system shaped over millions of years of human evolution. In the 2025 review “The Physiology of Hunger”, Alessio Fasano explains how hunger evolved and why modern food environments challenge that biology. He frames hunger as a multidimensional process involving the brain, gut, hormones, and even gut microbes. 

Fasano emphasizes that hunger is not a single signal but a complex interplay of mechanisms that once ensured survival but now, in a world of abundant food, can misfire in ways that promote overeating, obesity, and metabolic disease. 

Homeostatic Hunger: The Body’s Energy Balance System

Homeostatic hunger is the most ancestral and fundamental driver of eating—our biological need for energy. Fasano describes this system as involving intricate communication between the gut and the hypothalamus in the brain. Signals such as the hormone ghrelin rise when the stomach is empty, telling the brain that energy is needed. At the same time, gut-brain neural pathways—including vagal afferents—relay information about nutrient depletion and intestinal activity. Studocu

Once food enters the digestive tract, satiety signals gradually build. Stretch receptors in the stomach respond to volume and tension, and hormones like GLP-1, peptide YY (PYY), and cholecystokinin (CCK) are released in response to nutrients in the intestine, signalling fullness to the brain. Eventually, rising levels of plasma glucose, amino acids, and insulin complete the satiety response. This elegant hormonal and neural feedback loop evolved to maintain metabolic balance and ensure energy needs are met without overeating. Studocu

Fasano notes that this regulatory machinery evolved during times when food was unpredictable, favoring mechanisms that encouraged food intake and energy storage. In today’s constant food availability, the system can be coopted, leading to weight gain and metabolic dysfunction.

Why it matters

Ignoring homeostatic hunger can lead to:

• Hormonal imbalance

• Muscle loss

• Metabolic slowdown

• Increased binge-eating later

Hedonic Hunger: Pleasure Drives Eating Beyond Need

Fasano makes a clear distinction between physiological hunger and hedonic or appetite-driven eating, where pleasure—not energy need—drives food intake. In environments with abundant high-calorie, palatable foods, reward brain circuits often override homeostatic controls. These reward pathways involve dopamine and other neurotransmitters that make energy-dense foods feel especially desirable. Studocu

Unlike homeostatic hunger, hedonic hunger can be triggered by sensory cues (sight, smell, taste) and emotional states such as stress or boredom. Even in the absence of energy deficit, the anticipation or experience of palatable food activates reward-related brain circuits and encourages eating for pleasure. Traditional social and cultural factors (like food advertising or norms around food as comfort) further amplify this type of eating. Studocu

Fasano explains that this has significant health consequences: frequent hedonic eating contributes to excessive calorie intake, weight gain, and associated chronic diseases like type 2 diabetes and cardiovascular disease. Studocu

Why it matters

Chronic hedonic eating can lead to:

• Overeating despite fullness

• Insulin resistance

• Weight gain

• Food addiction-like behaviour

Microbiota-Driven Hunger: The Gut Microbiome’s Influence

One of the most cutting-edge ideas highlighted in Fasano’s review is the role of the gut microbiota in modulating hunger signals. The gut is home to trillions of microbes that communicate with the host through metabolic byproducts, neuroactive compounds, and immune-related mechanisms—a connection often called the gut–brain axis. 

Although the precise mechanisms remain an active area of research, the NEJM article suggests that gut microbes may influence host hunger and appetite signals by producing metabolites that mimic or modulate hormones involved in hunger regulation. These microbial signals can affect central nervous system pathways and contribute to food preferences, cravings, and even energy balance. 

In the context of modern diets high in processed foods and low in fiber, microbial communities may shift in ways that promote cravings for unhealthy foods, further amplifying hedonic eating and disrupting normal appetite regulation. 

Why it matters

An imbalanced microbiome (dysbiosis) can contribute to:

• Cravings that feel “out of control”

• Emotional eating

• Metabolic disorders

• Chronic inflammation

  
  

  

Why Understanding Hunger Matters Today

Fasano’s review brings evolutionary context to why hunger mechanisms can go awry in contemporary settings. What once promoted survival in scarce environments may now promote metabolic risk in a world of caloric abundance. The paper also highlights that advances in understanding hunger physiology are beginning to inform new therapeutic strategies, including pharmacologic agents that modulate satiety signals. 

Recognizing the multiple, interconnected drivers of hunger helps shift the conversation from willpower and “self-control” toward biology-informed strategies for nutrition and health. This perspective opens opportunities for personalized interventions that address not just what we eat, but why we eat. 

Conclusion: Hunger as Complex Biology, Not Simple Craving

According to The Physiology of Hunger, hunger emerges from three interlinked biological systems:

• Homeostatic mechanisms that ensure energy balance and survival;

• Hedonic pathways that reward pleasure and drive eating beyond need;

• And microbiota-driven signals that reflect the influence of gut microbes on appetite. 

Understanding these mechanisms helps us appreciate that hunger is not a single signal but a sophisticated, multilayered physiology. By applying these insights, we can better design dietary recommendations, behavioral interventions, and even medical therapies that align with how the body actually regulates eating—rather than treating hunger as a moral failing or simplistic urge.