The question of how many calories are burned when smoking cannabis does not have a simple numerical answer. The overall impact on energy expenditure is a complex interplay between the drug’s direct physiological effects and the subsequent changes it causes in a person’s behavior and eating habits. Any momentary increase in calorie burn must be weighed against the potential for significantly higher caloric intake and reduced physical activity. Understanding the total effect requires looking beyond the immediate act of smoking to the body’s metabolic response.
The Negligible Direct Calorie Cost
The physical process of inhaling and exhaling smoke or vapor expends an extremely small amount of energy. The action relies primarily on the diaphragm and intercostal muscles, which are already used for standard respiration. This muscular effort is comparable to taking a few slow, deep breaths, which barely registers above the body’s resting metabolic rate. The energy cost is considered so insignificant that it is not a measurable factor in daily calorie expenditure. The momentary increase in the work of breathing during the act of smoking contributes negligibly to this base rate. Therefore, the physical mechanics of using the substance do not provide a route for meaningful calorie burning.
Cardiovascular Effects and Metabolic Rate Changes
The primary way cannabis use can increase energy expenditure is through the psychoactive compound, delta-9-tetrahydrocannabinol (THC), which causes immediate cardiovascular stimulation. THC interacts with the body’s endocannabinoid system, leading to an acute elevation in heart rate, a condition known as tachycardia. This effect is dose-dependent and can be quite pronounced. Studies have shown that heart rate can increase by up to 34% higher than control values at rest. This increase in heart rate translates to a higher workload for the heart muscle and an overall increase in the body’s Resting Metabolic Rate (RMR). A faster heart rate means more oxygen is consumed by the body’s tissues, which raises the rate of calorie expenditure. This increased oxygen consumption (VO2) and metabolic activity suggest a temporary increase in calorie burning while the effects of THC are acute. However, the acute caloric increase from heart rate elevation is typically temporary and small in magnitude.
How Cannabis Influences Caloric Intake
Any temporary metabolic boost from cannabis is often overwhelmed by the dramatic change it causes in calorie intake, commonly known as the “munchies.” THC strongly stimulates appetite by interacting with Cannabinoid Receptor 1 (CB1) throughout the central nervous system, which promotes orexigenic pathways that increase the desire to eat. THC’s activation of CB1 receptors increases the concentration of ghrelin, often called the “hunger hormone.” Simultaneously, THC can reduce the body’s sensitivity to leptin, a hormone produced by fat cells that normally suppresses appetite and signals satiety. This hormonal shift is coupled with an enhanced sensory perception of food, making tastes and smells more pleasurable, which encourages overconsumption. The combination of increased hunger signals and blunted satiety signals leads to a significant increase in consumed calories, often from highly palatable, energy-dense snacks. Studies tracking consumption have shown that heavy cannabis users may consume hundreds of extra calories per day, sometimes estimated in the range of 582 to 834 more calories daily than non-users.
The Behavioral Impact on Energy Expenditure
Beyond the direct physiological and hormonal effects, the behavioral changes following cannabis use significantly influence Total Daily Energy Expenditure (TDEE). The most common acute behavioral effect is sedation or lethargy, often described as “couch lock.” This substantial reduction in non-exercise activity thermogenesis (NEAT) leads to a lower overall TDEE, counteracting any small calorie burn increase from the elevated heart rate. If a person chooses to sit or lie down for several hours after use, the calories burned are essentially reduced to their RMR. However, the behavioral response is highly individualized, and some people may report feeling motivated or more focused, which can lead to increased activity or exercise. In these specific cases, the mood-enhancing effects might facilitate a workout, thus increasing TDEE. Ultimately, the question of whether calories are burned or conserved depends far more on the user’s choice to remain sedentary or engage in physical activity than on the drug’s acute metabolic effects.