Vape e-liquid technically contains around 4-5 calories per millilitre, almost entirely from vegetable glycerine (VG), which is chemically a carbohydrate. Propylene glycol (PG) contains a smaller calorie value (around 4 calories per gram), nicotine contains essentially no calories, water contains zero, and flavour compounds contribute negligibly. A typical 2ml prefilled pod that lasts a UK vaper 1-3 days therefore contains around 10 total theoretical calories. A 10ml refill bottle contains around 40-50 theoretical calories.

However, the practical answer is essentially zero, because the lungs are not designed to absorb calories. Calorie absorption happens in the digestive system: food and drink enter the stomach and small intestine, where enzymes break down carbohydrates, fats and proteins, and the resulting nutrients are absorbed across the gut wall into the bloodstream. The lungs are designed for gas exchange (oxygen in, carbon dioxide out) and have no mechanism for absorbing carbohydrates or fats. PG and VG in vape vapour are exhaled along with the air, not absorbed as calories.

A small amount of vape vapour is condensed and swallowed rather than exhaled, which means a tiny fraction of e-liquid components do reach the digestive system. However, this is typically less than 5% of the total vape volume, and the resulting calorie contribution is too small to measure meaningfully. A 2ml pod fully swallowed would contribute about 10 calories, but in reality the swallowed fraction is around 0.5 calories per pod. For comparison, a single biscuit contains 50-100 calories, a banana contains around 100 calories, and a sugary drink can be 150-250 calories. The vape contribution to daily calorie intake is therefore biologically insignificant.

Why lungs do not absorb calories (the biology)

The lungs and the digestive system serve different functions. The lungs are designed for gas exchange across the alveolar membrane, a thin barrier between the air spaces in the lungs and the capillary blood vessels. The alveolar membrane is permeable to small molecules like oxygen (32 daltons), carbon dioxide (44 daltons) and nicotine (162 daltons), which is why these are absorbed effectively when vaped. Glycerine (VG, 92 daltons) and propylene glycol (76 daltons) can also cross the alveolar membrane, but they are not metabolised by the lungs as fuel. Glucose and fats (the energy molecules the body uses) require digestion before absorption, which happens in the gut, not the lungs. The body cannot use VG or PG inhaled as fuel because they are not in a form the cells can metabolise from blood. The result: calorie content of vape is biologically irrelevant.

Does vaping break intermittent fasting?

No. Intermittent fasting works by maintaining a fasted metabolic state (low insulin, fat-burning, autophagy activation) for extended periods. Three things break a fast: caloric intake high enough to trigger insulin response (generally accepted as more than 10-50 calories depending on the fasting protocol), protein intake (triggers gluconeogenesis), and any food that activates digestion. Vaping does none of these. The minimal calorie content of vape is not enough to trigger insulin response, the lungs do not activate gut digestion, and the small fraction swallowed is too tiny to register metabolically. UK intermittent fasting practitioners can vape during fasting periods without breaking ketosis or autophagy. Some protocols are more strict than others; if in doubt, water-only fasting is the safest.

Why some vapers gain or lose weight (not from calories)

Vapers occasionally report weight changes after starting or stopping vape. These changes are NOT from vape calories but from nicotine’s effects on appetite and metabolism. Nicotine suppresses appetite (acts on hypothalamic hunger pathways), slightly raises resting metabolic rate (around 50 extra calories per day), and can substitute for the hand-to-mouth habit of snacking. Stopping vape reverses these effects and typically results in 2-5kg weight gain in the first year of quitting. This is a well-documented effect of nicotine withdrawal, common to all forms of nicotine cessation (smoking, vape, pouches). The vape itself contributes no meaningful calories; the nicotine’s metabolic effects do drive weight changes.

For UK vapers concerned about diet, weight or fasting, the four-point framework below addresses the most common practical questions.

For UK vapers managing weight loss or fitness goals, focus on diet, exercise and sleep rather than vape calorie content. The vape contribution to daily calorie intake is biologically irrelevant. If you are noticing weight changes around vape use (gain when stopping, loss when starting), the cause is nicotine effects on appetite and metabolism, not vape calories. NHS and Cancer Research UK explicitly advise against using vape or nicotine as a weight management tool. Our Omagh and Strabane teams can advise on stepping down nicotine for vapers who want to manage the weight effects of nicotine cessation gradually.