The answer to whether smiling burns calories is yes, though the amount is so minimal that it is negligible in a person’s total daily energy expenditure. A calorie is a unit of energy, and any physical action, no matter how small, requires the conversion of stored chemical energy into mechanical work by muscles. For smiling, this metabolic process is localized and extremely low, requiring only a fraction of a single calorie.
The Energy Cost of Facial Movement
Moving any muscle, including those that control facial expression, requires fuel in the form of Adenosine Triphosphate (ATP). Muscle contraction involves the hydrolysis of ATP, which releases the energy needed for muscle fibers to shorten. Since a smile is typically a brief, low-resistance movement, the total ATP consumption is minuscule. The primary muscle responsible for smiling is the zygomaticus major.
This muscle is tiny compared to major skeletal muscle groups in the limbs or torso. Because the muscle mass involved is so small, the demand for ATP is extremely low, translating to an insignificant caloric cost. Even maintaining a sustained smile for several minutes requires a localized energy flow far below a measurable amount.
Smiling vs. Major Energy Expenditure
The body’s overall energy budget is dominated by processes unrelated to facial movement. The vast majority of calories burned daily are consumed by the body’s resting metabolism, which supports continuous functions like breathing, maintaining body temperature, and brain activity. These involuntary processes account for the largest percentage of total daily energy use.
Comparing a smile to any form of physical exercise highlights the difference in scale. When walking or running, large skeletal muscles in the legs and core are repeatedly recruited, demanding significant and sustained energy production. These major muscle groups require a high volume of ATP to power their contractions, which drastically increases the metabolic rate. The localized energy cost of a smile is a rounding error when measured against the energy consumers elsewhere in the body.
The Indirect Metabolic Effects of Laughter
While a simple smile has a negligible energy cost, the more vigorous, systemic action of genuine laughter offers a small but measurable increase in caloric expenditure. Laughter is a physical activity involving the respiratory and musculoskeletal systems. Sustained laughter forces rapid, deep contractions of the diaphragm and abdominal muscles, which are much larger than the facial muscles.
Studies using controlled environments have found that 10 to 15 minutes of genuine laughter can burn between 10 and 40 calories, depending on the person and the intensity. This effect is driven by a temporary increase in heart rate, which can be elevated by 10 to 20 percent above resting levels. This systemic activation of the cardiovascular and respiratory systems requires higher oxygen intake and greater fuel consumption, raising the metabolic rate.
This increased caloric burn is directly linked to the duration and intensity of the laughter. Therefore, while a brief, polite smile offers no meaningful metabolic effect, a deep, sustained bout of laughter results in a modest but real energy expenditure due to the involvement of large supporting muscles.