Vaping involves heating a liquid solution (e-liquid) to produce a breathable aerosol. The primary components are propylene glycol, vegetable glycerin, flavorings, and often nicotine. While these ingredients possess a theoretical caloric value, the method of consumption—inhalation—renders the caloric contribution metabolically insignificant to the diet.
The Caloric Potential of E-Liquid Components
The foundation of e-liquids rests on two main compounds: Propylene Glycol (PG) and Vegetable Glycerin (VG). Both are alcohols, and when consumed orally, they are metabolized by the body similar to carbohydrates. Vegetable Glycerin is classified as a sugar alcohol and provides about 4.3 kilocalories per gram when consumed as a food additive. Propylene Glycol is likewise metabolized, yielding about 4 kilocalories per gram. Although flavorings are included, their concentration is so low that their caloric impact is negligible even if fully absorbed.
Absorption Versus Ingestion of Vaping Aerosol
The critical distinction in caloric calculation is the difference between ingestion and inhalation. When food is ingested, the digestive system breaks down the components, which are then absorbed through the intestinal walls for use as energy. Vaping, however, bypasses the entire digestive tract. Inhaling the aerosol means the PG and VG particles are deposited primarily in the airways and lungs, whose main function is gas exchange, not nutrient absorption. The vast majority of the aerosol mass, including the PG and VG particles, is immediately exhaled back into the atmosphere.
While a small fraction of these compounds may be absorbed systemically through the moist lining of the lungs and airways, the amount is minimal. The absorbed amount is considered metabolically negligible, meaning it does not supply the body with energy or affect daily caloric intake or weight regulation. The bulk of the caloric potential of e-liquid remains unconsumed, vanishing on exhalation.
Nicotine’s Indirect Effect on Weight Regulation
Although the caloric content of the aerosol is not a factor, vaping may still indirectly influence body weight due to the presence of nicotine. Nicotine is a stimulant and acts as an appetite suppressant, an effect mediated by its influence on neurotransmitters in the brain that regulate feelings of hunger and satiety. Nicotine consumption also slightly increases the body’s resting metabolic rate, meaning the body burns calories at a faster pace even when at rest. This combination of reduced appetite and increased energy expenditure can lead to a lower overall caloric intake. Weight gain associated with vaping is most common upon cessation, when the appetite-suppressing effect of nicotine is removed, often leading to increased food consumption.