This paper explores socio-demographic, economic and behaviour factors influencing body mass index (BMI) amongst 20 to 64 year old adults in Canada. BMI scores in Canada have increased, with gains stemming from disproportionate increases in female BMI. Econometric results indicate higher BMI scores for males, those born in Canada, those in food insecure homes and whites. Age-gender interactions suggest different patterns of BMI adjustment over the life of males and females; a pronounced inverse quadratic relationship between with age and male BMI is noted, while female BMI increases with age. Education, used as a gauge of inequality, is inversely related to BMI, while income has a muted effect. BMI is inversely related to level of physical activity, an effect which is more pronounced for females in Canada. BMI has an inverse quadratic relationship with smoking behaviour, with higher BMI amongst former smokers than daily, occasional and non-smokers. BMI appears to be inversely related to intensity of alcohol consumption.