Introduction

Nicotine dependence, as defined by the Mayo Clinic,¹ arises when a person becomes addicted to nicotine, the primary addictive substance found in tobacco products. Once the body becomes accustomed to regular nicotine intake, the person begins to crave the substance, making cessation both physically and psychologically challenging. Understanding how nicotine interacts with the body’s hunger signals and metabolic rate is essential to better manage withdrawal symptoms and support long-term recovery.¹ Nicotine dependence, and the withdrawal symptoms that follow, are deeply personal experiences that can vary significantly from one individual to another. Factors such as genetic makeup, duration and intensity of nicotine use, mental health status, and overall lifestyle all influence how a person responds to the process of quitting tobacco. Despite this high degree of individual variation, there are several well-documented withdrawal symptoms that many people commonly report when they attempt to stop smoking or using nicotine products.

According to the U.S. Centers for Disease Control and Prevention (CDC), individuals may experience a range of physical, emotional, and psychological symptoms during withdrawal.² These include:

• Powerful cravings or urges to smoke that can feel overwhelming and difficult to resist, especially in familiar environments or situations associated with tobacco use
• Irritability, frustration, or anger, often triggered by minor inconveniences or stressors, as the body and brain adjust to functioning without nicotine
• Restlessness and heightened levels of stress, making it hard to relax or feel at ease
• Difficulty focusing or concentrating, which can affect daily productivity at work, school, or in routine tasks
• Feelings of anxiety, low mood, or even depressive symptoms, which may be temporary but still challenging to manage
• Disruptions to sleep, such as trouble falling asleep, waking frequently during the night, or not feeling rested after sleep
• An increase in appetite, particularly for sugary or high-calorie foods, which can contribute to weight gain during the withdrawal period

These symptoms typically begin within the first few hours after the last nicotine use and may last from a few days to several weeks, depending on the person.² For many individuals trying to quit smoking or using nicotine products, one common but often overlooked side effect is a noticeable change in appetite and metabolism. These physiological can contribute to weight gain and other health concerns during the withdrawal period, which may make it harder for some to stay committed to quitting. Nicotine cessation, or the process of quitting nicotine, leads to a complex interplay of neurological and endocrine (hormonal) changes. These changes are primarily driven by the body's adaptation to the absence of nicotine, which had previously altered various neurotransmitter systems (process of chemical messengers transmitting signals from one neuron to another) and hormonal balances. Understanding these changes is crucial for developing effective strategies to manage withdrawal symptoms and improve cessation outcomes. These symptoms are a result of nicotine withdrawal because your body can feel uncomfortable due to being previously dependent on nicotine for its daily function. Withdrawal symptoms do not usually persist, although it can take time, the best thing to do is not to indulge the urge to smoke again when the withdrawal symptoms appear, as these symptoms are actually a sign that your body is recovering from the effects of smoking.³

How nicotine affects appetite and metabolism

Nicotine is recognised for its ability to inhibit appetite and diminish food consumption during periods of active usage. Conversely, the cessation of nicotine results in a reinstatement of these effects, culminating in heightened appetite and increased food intake. This phenomenon primarily occurs due to nicotine's modulation of hypothalamic neuropeptides (messengers made of small amino acid chains used in the communication between neurons linked to the hypothalamus), including pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART), which play pivotal roles in the regulation of appetite. During the process of nicotine withdrawal, alterations in these peptides transpire, consequently leading to augmented hunger and food intake.^4,5

Research conducted on rodent models indicates that the cessation of nicotine intake induces modifications in metabolic profiles within the hippocampus, a neurological area involved in the regulation of energy homeostasis, thereby influencing neurotransmitter concentrations and potentially resulting in neuropsychiatric disorders.⁶ This underscores the biological foundations of withdrawal manifestations.

Moreover, scientific research has demonstrated that nicotine plays a significant role in increasing total energy expenditure in the body. It does this primarily by stimulating thermogenesis, the process by which the body generates heat by burning calories, and by boosting overall physical activity levels. Essentially, nicotine acts as a metabolic stimulant, encouraging the body to burn more energy even while at rest. However, when an individual stops using nicotine, this stimulatory effect on metabolism is taken away. As a result, the body’s ability to burn calories efficiently is reduced, leading to a noticeable drop in overall energy expenditure. This metabolic slowdown, coupled with potential increases in appetite during withdrawal, often contributes to gradual weight gain in individuals who are trying to quit nicotine.^7,8

Moreover, in rats it has also been shown that nicotine promotes fat metabolism by reducing the respiratory exchange ratio, indicating increased fat utilisation over carbohydrate metabolism.⁹

Nicotine withdrawal leads to increased appetite as the appetite-suppressant effects of nicotine are reversed, resulting in heightened hunger and food intake.¹⁰ This is attributed to nicotine's complex effects on appetite-regulating peptides and its stimulation of energy expenditure and metabolic rate.⁹ 

How to manage appetite changes when quitting

To effectively manage the appetite changes that accompany nicotine withdrawal, it is essential to adopt strategies that address both the psychological and physiological dimensions of this transition. Engaging in regular physical activity can help mitigate weight gain by enhancing energy expenditure and improving insulin sensitivity.

Additionally, incorporating a balanced diet rich in fiber and protein can promote satiety and reduce cravings, thereby supporting healthier eating habits during this challenging period. Behavioral interventions, such as mindfulness and cognitive-behavioral therapy (CBT), can also be beneficial, as they help individuals develop coping mechanisms to deal with increased hunger and emotional eating triggered by withdrawal symptoms.¹¹ Ultimately, a comprehensive approach that combines dietary modifications, physical activity, and psychological support can empower individuals to navigate the complexities of nicotine withdrawal more effectively.

Long-term outlook and summary

Whilst the health benefits of quitting nicotine far outweigh the risks associated with short-term weight gain, it is important to acknowledge that excessive or rapid weight gain can pose a genuine obstacle to sustained quitting. For some individuals, the fear of gaining weight may deter them from attempting to quit, or may even lead to relapse during the withdrawal phase. Nonetheless, these challenges can be effectively managed with the assistance of healthcare professionals. By consulting a doctor, dietitian, or smoking cessation advisor, individuals can develop practical, personalised strategies to help manage their weight while remaining nicotine-free.

Nicotine is a highly addictive substance, and when an individual decides to stop using it, the body may respond with a range of withdrawal symptoms. These symptoms, such as irritability, low mood, increased appetite, tiredness, and cravings, can vary in intensity depending on factors such as a person’s metabolism, body composition, and the amount of nicotine previously consumed. Understandably, these symptoms can feel overwhelming in the early stages of withdrawal, leading some people to return to nicotine use as a means of relief. The NHS offers an informative segment on how to give yourself a better chance of quitting, by combining nicotine replacement therapies (NRT), such as nicotine-free medicines, patches, gum and nasal sprays, as well as other behavioural advice; you can ask a GP or a local Stop Smoking Service for more information about the products available to you.³

However, it is crucial to remember that the long-term health advantages of quitting nicotine, such as a reduced risk of cancer, heart disease, stroke, and respiratory problems, far outweigh any temporary discomfort experienced during withdrawal. Should withdrawal symptoms become difficult to cope with, medical advice and support services are readily available. Seeking help not only makes withdrawal more manageable but also greatly increases the chances of remaining nicotine-free in the long term.