An Australian study involving more than 450,000 smokers has found that the weight gained by those who gave up smoking was significantly less than expected.

The study conducted by Tasmania's Menzies Institute for Medical Research surveyed 388,432 daily smokers and 63,403 people who'd recently quit smoking and compared their weight differences over a five-year period.

Results showed that, on average, those who quit smoking gained an average of 4.1 kilograms over the life of the study, while those who continued smoking gained just 1.5 kg, meaning the overall weight gain for the "quitters" was a surprisingly small 2.6 kg.