Study: Trends in weight change among Canadian adults

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Canadian adults keep putting on weight, but indications are that the pace at which they are gaining has slowed down, according to a new report.

The report was based on data from the National Population Health Survey, a longitudinal survey that has followed the same group of people every two years, on six separate occasions, between 1994/1995 and 2004/2005. Data for height and weight for this survey were self-reported. This study is based on data from 1996/1997 to 2004/2005.

The survey showed that every two years since 1996/1997, adults aged 18 to 64 were heavier on average.

But while they continued to gain weight, the amount they put on decreased significantly in the most recent two-year interval, 2002/2003 to 2004/2005.

This downturn was due in part to a statistically significant decrease in the proportion of men who gained weight and a significant increase in the amount of weight loss among women who lost weight.

However, among people who gained weight, the amount they put on actually increased over time.

During the eight years covered by the study, men gained an average of 4.0 kg, while women gained an average of 3.4 kg. While these results appear relatively small, a number of studies have shown that even a small shift in the population distribution toward excess weight may have important consequences for the incidence of weight-related diseases.

Rate of gain slowing

Canadians are still gaining weight, on average. But this report found that the pace at which they are gaining has slowed down.

Over the two-year interval from 1996/1997 to 1998/1999, the average self-reported weight of people aged 18 to 64 increased by 1.0 kg for men and 0.9 kg for women.

Between 2000/2001 and 2002/2003, average gains were higher: 1.1 kg for men and 1.0 kg for women.

Over the next two years, that is, 2002/2003 to 2004/2005, the weight of adults continued to rise. However, the average amount gained was lower: 0.7 kg for men and 0.6 kg for women.

Thus, overall adults were still gaining weight, but statistically significantly less than in the earlier periods.

Weight changes associated with sex, age and level of obesity

Changes in weight were significantly associated with sex, age group and the level of obesity as measured by the body mass index (BMI).

Over the eight years from 1996/1997 to 2004/2005, the average self-reported weight of men and women in all age groups increased.

However, in each two-year interval, younger people aged 18 to 33 experienced significantly greater average gains than did individuals aged 34 to 49. Older adults aged 50 to 64 experienced significantly smaller gains than 34 to 49 year-olds.

The general trend of a decline in the amount of weight gained between 2002/2003 and 2004/2005 applied to men and women in most age groups. The exception was men aged 18 to 33, whose average weight gain in the most recent two-year interval was greater than that in the previous one.

An individual's BMI is associated with how much his or her self-reported weight changed in each two-year interval.

On average, overweight people (BMI from 25.0 to 29.9) gained 0.8 kg less than did people whose weight was in the acceptable BMI range (BMI from 18.5 to 24.9). Obese individuals (BMI 30.0 and higher) gained 1.9 kg less. In fact, during most two-year intervals, people who were obese experienced a mean loss in self-reported weight.

Smaller proportion of men gaining weight

The overall pattern of average change in weight in the last interval (2002/2003 to 2004/2005) reflects a mixture of trends at a finer level of detail. These include a smaller proportion of men gaining weight and greater losses among the women who lost weight.

During each of the first three two-year intervals in the survey, almost half of adults reported that they gained weight. However, between 2002/2003 and 2004/2005 the proportion of men gaining weight fell to 44%.

As well, 32% of men reported a loss in weight between 2002/2003 and 2004/2005, a significantly higher percentage than in the first two intervals.

Among women, the proportion losing weight did not differ significantly from one interval to another.

Definitions, data sources and methods: survey number 3225.

This release is based on the article "Trends in weight change among Canadian adults: Evidence from the 1996/1997 to 2004/2005 National Population Health Survey," the first of a series to be released in Volume 2 of the Internet publication Healthy Today, Healthy Tomorrow? Findings from the National Population Health Survey, Vol. 2, no. 1 (82-618-MIE2006005, free), now available from the Publications module of our website.

Data from the sixth cycle of the household component of the National Population Health Survey (NPHS), covering the 1994/1995 to 2004/2005 period are also available today.

This article is scheduled to be presented today (November 6, 2006) in Ottawa at the second national conference of the Chronic Disease Prevention Alliance of Canada, with the theme Integrated Chronic Disease Prevention: Building It Together. Three other presenters from Statistics Canada are to discuss papers using NPHS Cycle 6 data.

For more information or to enquire about the concepts, methods or data quality of this article, contact Heather Orpana (613-951-1650; heather.orpana@statcan.gc.ca), Health Analysis and Measurement Group.

NPHS micro data are available at Statistics Canada's Research Data Centres. For more information, visit The Research Data Centres Program page of our website.

To order custom tabulations, contact Data Access and Information Services (613-951-1746; hd-ds@statcan.gc.ca), Health Statistics Division.

For further information on the Household Component of the National Population Health Survey, or to enquire about the concepts, methods or data quality of this release, contact Mario Bédard (613-951-8933; mario.bedard@statcan.gc.ca) or France Bilocq (613-951-6956; france.bilocq@statcan.gc.ca), Health Statistics Division.