'If I quit, I'll put on weight.' That is the number one worry of smokers who hesitate to stop. You are about to discover that reality is less awful — and far more controllable — than what you have in mind.

How many kilos, really?

A major meta-analysis published in the British Medical Journal (Aubin et al., 2012) pooled 62 studies on the subject. Conclusion:

The precise timeline, month by month:

1. 1 month around +1.1 kg
2. 2 months around +2.3 kg
3. 3 months around +2.9 kg (the bulk is done)
4. 6 months around +4.2 kg
5. 12 months around +4.7 kg
6. At 2-3 years stabilisation, sometimes a return close to the initial weight for some people.

And the distribution is more reassuring than commonly believed: 16 to 21% of ex-smokers lose weight in the first year. It is neither automatic nor inevitable.

Why the body gains weight: three mechanisms

1. Metabolism slows down

Nicotine speeds up your basal metabolism by about 10%, meaning 200 extra calories burned per day doing nothing — the equivalent of a croissant. When you quit, your metabolism returns to normal operation. You no longer 'burn while sleeping' like before.

2. Appetite comes back

Nicotine is a powerful appetite suppressant: it modulates leptin (satiety hormone), ghrelin (hunger hormone) and neuropeptide Y. When you quit, these hormones resume their natural activity. You rediscover a real appetite — which is healthy, but destabilising.

3. Taste and smell return

48 to 72 hours after the last cigarette, your taste buds wake up. Food becomes more flavourful, food more tempting. This is also when many ex-smokers turn to sugar — the brain looks for a new source of reward.

Myth vs reality

Who gains the most weight?

Identified risk factors:

Conversely, people who smoked little (< 15 cig/day) have weight gain comparable to non-smokers over 10 years.

How to limit it (without becoming obsessed)

What if I lose weight when I quit?

It happens, and more often than you think (16-21% of cases). Three main explanations:

• Resumption of physical activity, with more motivation because you breathe better.

• Lower alcohol consumption, often correlated with quitting smoking.

• Healthier food choices, by cascade effect: 'I am looking after myself'.

And after the first 12 months?

Good news: weight gain stabilises after the first year. Many ex-smokers gradually return towards their initial weight over 2 to 5 years, especially if they keep up regular physical activity.

In United Kingdom

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