One of the most common reasons people give for smoking is that it helps them lose weight. The theory is that smoking suppresses appetite, so you eat less. It also increases energy expenditure, which means smokers burn calories slightly faster. But on the whole, there’s a rapidly expanding body of evidence showing that by itself, smoking actually makes people gain weight. This is because cigarettes contain a cocktail of chemicals with a number of effects. While some of the ingredients promote weight loss, others actually make a hefty contribution to weight gain.

OROGOLD has reviewed research investigating body weight in smokers and found similar results in several studies. Heavy smokers – a pack a day or more – tend to weigh more than non-smokers, but occasional smokers tend to be slimmer than those who abstain. Initially, it was thought that this was on account of heavy smokers usually having worse diets, lower income (which is correlated with weight-gain) and getting less exercise. However, when all these factors were accounted for, heavy smokers were still dis-proportionally overweight.

That’s why scientists decided to investigate further, and made some interesting discoveries. Firstly, while tobacco increases metabolism, the effects are slight. One cigarette only made people burn 3% more energy over the next half hour, while four cigarettes had them burning 3.3% more calories over the next few hours. In overweight people, this effect is even smaller. Either way, it’s not enough to compensate for the other ways tobacco makes you gain weight.

The thing is, smoking has a distinct impact on how the body responds to its own natural insulin. Put simply, one of insulin’s jobs is to decide which kind of energy to burn, and how much. Smoking increases insulin resistance which not only makes it particularly difficult to lose body fat, but also means sugary foods will hit your waist-line a lot harder. This is why heavy smokers are particularly at risk of type 2 diabetes. It’s a vicious cycle too. The more body fat a person has, the more their insulin resistance increases. Basically, cigarettes have a weight-gain effect that just keeps building on itself.

To make matters worse, quitting smoking doesn’t help with weight loss either. While cigarettes only make you burn about 3% more energy by increasing metabolism, you’ll start burning it about 15% more slowly after quitting. This effect can persist for up to a few years. It also takes a few years for the insulin resistance to repair itself.

At the end of the day, smoking is just a terrible way to lose weight. While it has mild weight-loss effects, this only works for light smokers over the short term. If you smoke too much or for too long, this quickly starts having the opposite effect. And when you quit, you’ll gain even more weight. You can try using cigarettes as a weight loss tool, but in the long run they’ll always make it harder, not easier.