Health Reports
The health consequences of obesity history and weight fluctuations in adulthood

Abstract

Background

The prevalence of Canadians living with obesity has increased over the past four decades. Disease and mortality risk increase as the number of years lived with obesity increases.

Methods

This study used self-reported weight history and health data collected from 2007 to 2011 via the Canadian Health Measures Survey (n = 5,761) to examine whether increased exposure to obesity during adulthood increases the odds of having poor health outcomes.

Results

The percentage of respondents with an obesity-related chronic condition was lower among those who did not have obesity at the time of survey or report having obesity in the past (50.6%) compared with those who did not have obesity at the time of the survey but did in the past (65.9%) or who had obesity at the time of the survey and in the past (71.1%). Relative to never having obesity, having obesity in the past but not at present or having obesity in the past and at present were associated with increased odds of having a range of chronic conditions. The highest odds were observed for type 2 diabetes (odd ratio (OR) = 3.26, 95% confidence interval (CI): 2.40 to 4.43 and OR = 5.36, 95% CI: 3.88 to 7.41), hypertension (OR = 2.41, 95% CI: 1.69 to 3.44 and OR = 3.76, 95% CI: 2.84 to 4.97), and poor or fair self-rated general health (OR = 2.04, 95% CI: 1.51 to 2.76 and OR = 2.68, 95% CI: 2.11 to 3.40).

Interpretation

Having had obesity in the past, regardless of current obesity status, was associated with increased odds of poor health outcomes. Obesity history information should be considered when estimating the population burden of obesity.

Keywords

weight history, body mass index, lifespan, cardiovascular disease

Authors

Rachel C. Colley, Tracey Bushnik and Joel Barnes are with the Health Analysis Division at Statistics Canada.

 

What is already known on this subject?

• 30% of Canadian adults have obesity (body mass index greater than or equal to 30.0 kg/m²).
• Obesity is a strong predictor of health complications including cardiovascular disease (CVD), type 2 diabetes and cancer.
• Compared with older generations, obesity is occurring earlier in the life course.
• Weight fluctuations are associated with an increased risk of chronic disease.

What does this study add?

• Having had obesity in the past, regardless of current obesity status, is associated with higher odds of having an obesity-related chronic condition, CVD, type 2 diabetes, hypertension, high cholesterol, arthritis, moderate-to-severe disability, pain preventing activity, or poor or fair general health. The odds of having these health conditions were higher among those who reported having obesity at the time of the survey and in the past compared with those who only reported having obesity in the past.
• Respondents who experienced one or more major weight fluctuations during adulthood or a difference between their highest and lowest adulthood body mass index (BMI) greater than or equal to 6.8 kg/m² were at increased odds of reporting poor or fair mental health.
• The odds of having an obesity-related chronic condition increases with age, regardless of current and past obesity status.
• Self-reported weight at age 25 was higher among adults under the age of 50 compared with adults older than 50 years. Younger adults gained more weight in the past 10 years compared with older adults.

Introduction

The prevalence of Canadian adults with obesity has been steadily increasing over the past four decades. Nine percent of Canadian adults had obesity in 1981,^Note 1 27.2% had obesity in 2018^Note 2 and the most recent estimates from 2022 indicate that 30% of Canadian adults have obesity.^Note 3 Obesity is a strong predictor of health complications including cardiovascular disease (CVD), type 2 diabetes, hypertension, liver and kidney diseases, and cancer.^Note 4

Cross-sectional research provides compelling evidence that obesity is related to health outcomes; however, one’s trajectory of body weight across the lifespan is important to consider when assessing risk for developing disease later in life.^Note 5 Research leveraging prospective cohort studies shows that there are important differences in downstream health outcomes resulting from the timing and length of exposure to obesity during adulthood. Obesity during adolescence and adulthood is associated with CVD and type 2 diabetes risk in adulthood.^Note 5, ^Note 6 While improvements in CVD risk are evident after weight loss, studies have shown that some arterial damage persists among healthy weight individuals with a history of obesity.^Note 7 Using the Australian Longitudinal Survey on Women’s Health, researchers observed that earlier onset and greater exposure to obesity were associated with the development of type 2 diabetes among women.^Note 8 Other research has linked obesity during midlife with an increased risk of cancer^Note 9 and mortality.^Note 10 Taken together, a growing body of research indicates that understanding the link between obesity and the incidence of disease later in life can be improved by examining datasets that include information about one’s obesity trajectory across the lifespan.

A nationally representative longitudinal cohort of Canadians that captures weight change information from young adulthood does not presently exist in Canada. The Canadian Health Measures Survey (CHMS) implemented a weight change questionnaire module in cycles 1 and 2 of the survey (2007 to 2011). The weight change module asks adult respondents to report their weight at specific historical time points, whether they had any major weight fluctuations, and what their highest and lowest weights were since age 18. A recent meta-analysis concluded that self-reported height and weight from early life are valid for epidemiological studies.^Note 11 Research conducted in the United States using the same weight change module showed that these weight history variables are associated with CVD risk, asthma, hypertension and mortality.^Note 12, ^Note 13, ^Note 14 The purpose of this study is to describe the obesity change pattern among Canadian adults aged 28 to 79 years and to examine associations between obesity history and health outcomes.

Methods

Data source

Data are from the CHMS, a repeated cross-sectional, nationally representative survey at Statistics Canada that collects self-reported and directly measured health information from the Canadian population living in private dwellings in the 10 provinces. People on reserves and settlements in the provinces, the institutionalized population, residents of certain remote regions, and full-time members of the Canadian Forces are excluded (about 4% of the Canadian population). Data collection in each cycle took place in two parts. First, a questionnaire on socio-demographic characteristics and health behaviours was administered at the respondent’s home. This was followed by an appointment at a mobile examination centre where additional questions were asked and a series of physical measurements were collected (e.g., height, weight and blood pressure). Ethics approval for the CHMS was obtained from Health Canada’s Research Ethics Board.^Note 15 More information about the CHMS is available elsewhere.^Note 16, ^Note 17 The study sample includes data collected from March 2007 to February 2009 (cycle 1) and from August 2009 to November 2011 (cycle 2). The study sample includes respondents aged 28 to 79 who responded to the weight change module. The total sample of pooled data (n = 5, 761) from cycles 1 and 2 of the CHMS includes 2,718 men and 3,043 women.

Weight change module

The CHMS weight change module asks respondents aged 28 years and older to report their current weight and their weight 1 year ago, 10 years ago and at age 25. Measured weight data are available in the CHMS for current weight only, so reported current weight values were used to ensure consistency in any self-report bias between current and historical weight responses. The average reported and measured weights for the sample were similar among men (reported: 85.5 kg [95% confidence interval (CI): 84.1 to 87.0] versus measured: 86.2 kg [95% CI: 84.7 to 87.6]) and women (reported: 70.4 kg [95% CI: 69.1 to 71.7] versus measured: 72.0 kg [95% CI: 70.7 to 73.3]). Respondents were asked to report the highest and lowest they ever weighed since age 18 (excluding pregnancy) and at what ages the lowest and highest weights occurred. Respondents were instructed to not report weight during pregnancy. If the time point being asked aligned with a time when they were pregnant, respondents were asked to report their weight just before becoming pregnant. The reported weight values were converted into body mass index (BMI) using current height to determine obesity status at each time point: normal (BMI less than 25.0 kg/m²), overweight (BMI equal to 25.0 kg/m² or less than 30.0 kg/m²) or obese (BMI greater than or equal to 30.0 kg/m²).

Obesity history: Respondents were classified into three obesity history categories: (1) currently non-obese (i.e., current reported BMI less than 30.0 kg/m²) and never reported having obesity at any of the specified time points (i.e., 1 year ago, 10 years ago, at age 25, and at the highest and lowest weight), (2) currently non-obese (i.e., current reported BMI less than 30.0 kg/m²) and reported having obesity at one or more of the specified time points (i.e., 1 year ago, 10 years ago, at age 25, and at the highest and lowest weight), (3) currently has obesity (i.e., current reported BMI greater than or equal to 30.0 kg/m²) and reported having obesity at one or more of the specified time points (i.e., 1 year ago, 10 years ago, at age 25, and at the highest and lowest weight). There were not enough respondents (n = 34) who currently had obesity with no history of having obesity to include this group in the analysis.

Weight fluctuation: Respondents were also asked whether they had experienced a major weight fluctuation since age 18 (defined in the questionnaire as having ever lost or gained more than 10 lb. [4 kg] within a single year [excluding pregnancy]) and how many times this type of weight fluctuation occurred.

BMI difference: The median gap between the lowest and highest BMI since age 18 in the study sample was 6.8 kg/m². Respondents were dichotomized into being below or at/above the median adulthood BMI gap (6.8 kg/m²).

Health outcomes

Respondents were asked to report long-term (six months and over) health conditions diagnosed by a health professional. Where sample size allowed, chronic conditions were included in the analysis on their own (i.e., arthritis, hypertension, high cholesterol and type 2 diabetes), while others were collapsed into clusters, including CVD and obesity-related chronic conditions.
CVD clustered variable:

• Do you have heart disease?
• Have you ever been told by a health professional that you have had a heart attack?
• Do you suffer from the effects of a stroke?

Obesity-related chronic conditions clustered variable:

• Do you have high blood pressure?
• Have you ever been told by a health professional that your blood cholesterol was high?
• Do you have type 2 diabetes?
• Do you have cancer?
• Have you ever been diagnosed with cancer?
• Do you suffer from kidney dysfunction or disease?
• Do you have liver disease or gallbladder problems?
• Do you have fibromyalgia?
• Do you have arthritis or rheumatism?

Self-rated general and mental health were dichotomized into poor or fair versus good, very good or excellent groups. The Health Utility Index (HUI) module contains a series of questions used to measure health status and health-related quality of life.^Note 18 The overall HUI score from this module (dichotomized into having a moderate to severe disability versus none or mild disability) as well as one sub-score describing whether pain prevents activity (dichotomized into pain preventing a few, some or all activities versus no pain or pain not preventing activities) were used as outcomes in the present analysis.

Covariates

Age ranges at the time of reporting were divided into 5 groups: 28 to 39 years, 40 to 49 years, 50 to 59 years, 60 to 69 years and 70 to 79 years. Sex was reported as male or female. Gender was not collected in cycles 1 or 2 of the CHMS. The highest level of respondent educational attainment was derived as less than secondary school education, secondary school graduation, and post-secondary degree or diploma. Income adjusted for household size was divided into quartiles. Marital status was dichotomized into married versus single, widowed, separated or divorced. Smoking status was dichotomized into daily smoker (yes or no) and alcohol consumption was dichotomized into regular drinker (two to three times per month or more) (yes or no). Physical activity was divided into active (energy expenditure 3 kcal/kg/day or more), moderately active (greater than or equal to 1.5 kcal/kg/day and less than 3 kcal/kg/day), inactive (less than 1.5 kcal/kg/day). Sedentary behaviour was dichotomized into less than 20 hours per week versus 20 hours or more per week of sedentary time. A proxy for diet quality (daily frequency of fruit and vegetable consumption) was derived.^Note 19

Statistical analysis

Proportions, means and 95% confidence intervals were estimated for categorical and continuous variables. The proportion of respondents with one or more chronic conditions; one or more obesity-related health conditions; poor or fair general and mental health; moderate to severe disability; and pain preventing activity were estimated according to obesity history, weight fluctuation and BMI difference. Differences in the proportion of respondents with health outcomes between obesity history, weight fluctuation, and BMI difference categories was assessed using contrast statements within the PROC DESCRIPT procedures in SAS-callable SUDAAN (version 11.0.3). Logistic regression, adjusted socio-demographic and behavioural covariates (see above) known to be associated with obesity were used to assess the likelihood of having a range of different obesity-related chronic conditions according to the different obesity history, weight fluctuation and BMI difference categories. Separate logistic regression models by age group were also used to assess whether the overall findings differed across age groups (the 60-to-69-year and 70-to-79-year age groups were collapsed for the age-segregated logistic regression analyses because of sample size limitations). A sensitivity analysis comparing minimally adjusted (i.e., age group, sex and education) versus fully adjusted (i.e., all socio-demographic and behavioural covariates) logistic regression models revealed no appreciable change in the odds of having various chronic conditions (data not shown). To account for the survey’s complex sampling design, all analyses were weighted using the CHMS cycles 1 and 2 combined survey weight. Variance estimation (95% confidence intervals) was done using the replicate weights generated by Statistics Canada. The data were analyzed with SAS 9.4, SAS-callable SUDAAN 11.0.3 and RStudio version 4.2.3 using 24 denominator degrees of freedom in all procedure statements.

Results

Descriptive statistics

The unweighted sample size and weighted percentage distribution overall and by sex is provided for all variables in Table 1. More than half of the sample did not have obesity at the time of the survey and did not report a history of having obesity (61.4%) while 16.4% reported not having obesity at the time of the survey with some history of having obesity and the remaining 22.2% reported having obesity at the time of the survey and at one time point or more in the past. Over half of respondents (56.1%) reported having at least one major weight fluctuation since age 18 (defined as a change in body weight of at least 4 kg (10 lb.) within a single year) and 49.1% reported at least a 6.8 kg/m² difference between their highest and lowest adulthood BMI.



Weight history by age group

Sex-specific current reported weight did not differ across age groups, except for the average weight of 40-to-49-year-old women being higher than that of 28-to-39-year-old women and the average weight of 70-to-79-year-old men being lower than that of 28-to-39-year-old men (Table 2). Reported weight at age 25 declined with increasing age. Men aged 70 to 79 years at the time of the survey reported a weight at age 25 that was, on average, 8 kg (17.2 lb.) lower than the weight at age 25 reported by men aged 28 to 39 years at the time of the survey (Chart 1). Women aged 70 to 79 years at the time of the survey reported a weight at age 25 that was, on average, 6 kg (13.2 lb.) lower than the weight at age 25 reported by women aged 28 to 39 years at the time of the survey. The lowest weight since age 18 was also lower among older age groups compared with 28- to 39-year-olds. For example, the lowest weight in adulthood reported by men aged 70 to 79 years was, on average, 65.9 kg compared with 71.3 kg among men aged 28 to 39 years. Men and women aged 28 to 39 years also reported their lowest weight occurred at an average age of 20.1 to 21.5 years, while men and women aged 70 to 79 years reported their lowest weight occurred, on average, when they were 25 years.Average weight gain in the 10 years leading up to the survey (defined as the difference between one’s weight at the time of reporting and their weight 10 years prior) was lower among the older age groups (Chart 2). The average weight gain among 28- to 39-year-old men (7.6 kg) was higher than for all other age groups. Similarly, the average weight gain in the previous 10 years was higher among 28- to 39-year-old women (6.6 kg) compared with women aged 50 years or older.



Description of Chart 1



Data Table Chart 1
Table summary
This table displays the results of Data Table Chart 1 28 to 39 years, 40 to 49 years, 50 to 59 years, 60 to 69 years, 70 to 79 years, Mean and 95% confidence interval, calculated using from and to units of measure (appearing as column headers).

	28 to 39 yearsData Table Chart 1 Note †				40 to 49 years			50 to 59 years			60 to 69 years			70 to 79 years
	Mean		95% confidence interval		Mean	95% confidence interval		Mean	95% confidence interval		Mean	95% confidence interval		Mean	95% confidence interval
			from	to		from	to		from	to		from	to		from	to
Weight at age 25 (kg)
Men	78.8		77.2	80.4	77.5	75.4	79.6	73.4Note ***	71.9	75.0	72.9Note ***	71.6	74.2	70.8Note ***	69.3	72.3
Women	62.0		60.2	63.9	59.6Note *	58.3	61.0	56.8Note ***	55.6	58.1	56.1Note ***	55.1	57.1	56.0Note ***	54.8	57.2
Note * significantly different to reference category (p < 0.05) Return to note * referrer Note *** significantly different to reference category (p < 0.001) Return to note *** referrer Note † reference category Return to note † referrer Source: 2007 to 2009, 2009 to 2011 Canadian Health Measures Survey, combined.

Description of Chart 2



Data Table Chart 2
Table summary
This table displays the results of Data Table Chart 2 28 to 39 years, 40 to 49 years, 50 to 59 years, 60 to 69 years, 70 to 79 years, Mean and 95% confidence interval, calculated using from and to units of measure (appearing as column headers).

	28 to 39 yearsData Table Chart 2 Note †			40 to 49 years			50 to 59 years			60 to 69 years			70 to 79 years
	Mean	95% confidence interval		Mean	95% confidence interval		Mean	95% confidence interval		Mean	95% confidence interval		Mean	95% confidence interval
		from	to		from	to		from	to		from	to		from	to
Difference between current weight and weight 10 years ago (kg)
Men	7.6	6.5	8.8	3.0Note *** Note E: Use with caution	1.3	4.6	4.3Note *	2.8	5.7	1.9Note *** Note E: Use with caution	1.1	2.8	0.8Note * Note E: Use with caution	-0.1	1.8
Women	6.6	5.1	8.2	5.8	4.4	7.2	4.6Note *	3.5	5.8	3.1Note *** Note E: Use with caution	1.9	4.3	1.6Note *** Note E: Use with caution	0.6	2.6
E use with caution Note * significantly different to reference category (p < 0.05) Return to note * referrer Note *** significantly different to reference category (p < 0.001) Return to note *** referrer Note † Reference category Return to note † referrer Source: 2007 to 2009, 2009 to 2011 Canadian Health Measures Survey, combined.

Health outcomes by obesity history

The proportions of respondents with each of the selected negative health outcomes are presented in according to obesity history (Chart 3), weight fluctuation (Chart 4) and adulthood BMI difference (Chart 5). Except for mental health, there was a higher proportion of respondents with negative health outcomes if they had a history of obesity, regardless of whether or not they were obese at the time of the survey (Chart 3). For example, the percentage of respondents with an obesity-related chronic condition was lower among those who never had obesity (50.6%) compared with those who did not have obesity at the time of the survey but did in the past (65.9%) or who had obesity at the time of the survey and in the past (71.1%). Having experienced a major weight fluctuation was not associated with an increased proportion of respondents with obesity-related chronic conditions; however, it was associated with an increased percentage of respondents with mobility and musculoskeletal outcomes including arthritis or rheumatism, pain preventing activity, disability, as well as poor or fair self-rated general and mental health (Chart 4). Having a difference between one’s highest and lowest adulthood BMI greater than or equal to 6.8 kg/m² was associated with an increased likelihood of having all the negative health outcomes examined (Chart 5). For example, respondents were more likely to have an obesity-related chronic condition if the difference between their highest and lowest adulthood BMI values was greater than or equal to 6.8 kg/m² (67.7%) compared with those with a difference of less than 6.8 kg/m² (48.0%).

Description of Chart 3



Data Table Chart 3
Table summary
This table displays the results of Data Table Chart 3 Percentage and 95% confidence interval, calculated using from and to units of measure (appearing as column headers).

	Percentage	95% confidence interval
		from	to
Poor or fair mental health
Has obesity with history of obesity	5.1	3.5	7.5
Does not have obesity with history of obesity	6.9	4.2	11.1
Never had obesityData Table Chart 3 Note †	4.6	3.5	6.0
Poor or fair general health
Has obesity with history of obesity	18.9Note ***	16.3	21.9
Does not have obesity with history of obesity	14.8Note ***	11.4	19.0
Never had obesityData Table Chart 3 Note †	7.9	6.6	9.4
Pain that prevents activity (HUI)
Has obesity with history of obesity	26.4Note ***	22.0	31.3
Does not have obesity with history of obesity	18.7Note *	14.8	23.4
Never had obesityData Table Chart 3 Note †	12.3	10.8	14.1
Moderate or severe disability (HUI)
Has obesity with history of obesity	39.3Note ***	34.8	43.9
Does not have obesity with history of obesity	32.1Note *	27.0	37.6
Never had obesityData Table Chart 3 Note †	25.6	23.3	28.0
Arthritis or rheumatism
Has obesity with history of obesity	27.7Note ***	24.5	31.2
Does not have obesity with history of obesity	20.9Note *	18.0	24.1
Never had obesityData Table Chart 3 Note †	15.3	13.6	17.1
High cholesterol
Has obesity with history of obesity	33.4Note ***	29.2	37.9
Does not have obesity with history of obesity	33.9Note ***	29.8	38.3
Never had obesityData Table Chart 3 Note †	20.9	18.9	23.0
Hypertension
Has obesity with history of obesity	34.3Note ***	30.1	38.8
Does not have obesity with history of obesity	28.7Note ***	23.6	34.3
Never had obesityData Table Chart 3 Note †	13.5	12.0	15.1
Type 2 diabetes
Has obesity with history of obesity	11.3Note ***	9.0	14.0
Does not have obesity with history of obesity	7.9Note ***	5.9	10.3
Never had obesityData Table Chart 3 Note †	2.2	1.8	2.7
Cardiovascular diseaseData Table Chart 3 Note 2
Has obesity with history of obesity	10.6Note ***	8.4	13.4
Does not have obesity with history of obesity	10.9Note ***	8.3	14.3
Never had obesityData Table Chart 3 Note †	4.9	4.0	5.9
Obesity-related chronic conditionData Table Chart 3 Note 1
Has obesity with history of obesity	71.1Note ***	65.5	76.0
Does not have obesity with history of obesity	65.9Note ***	61.3	70.2
Never had obesityData Table Chart 3 Note †	50.6	48.0	53.2
Note * significantly different from reference category (p < 0.05) Return to note * referrer Note *** significantly different from reference category (p < 0.001) Return to note *** referrer Note † reference category Return to note † referrer Note 1 Includes respondents who reported having one or more of: fibromyalgia, arthritis or rheumatism, back problems, hypertension, high cholesterol, type 2 diabetes, heart disease, had a heart attack, cancer (present or past), suffering from the effects of a stroke, kidney dysfunction or disease, liver or gallbladder problems. Return to note 1 referrer Note 2 Includes respondents who reported having heart disease, having had a heart attack or suffering from the effects of a stroke. Return to note 2 referrer Note: HUI: Health Utility Index. Source: 2007 to 2009, 2009 to 2011 Canadian Health Measures Survey, combined.

Description of Chart 4



Data Table Chart 4
Table summary
This table displays the results of Data Table Chart 4 Percentage and 95% confidence interval, calculated using from and to units of measure (appearing as column headers).

	Percentage	95% confidence interval
		from	to
Poor or fair mental health
1+ weight fluctuation ≥ 4kg	18.5Note *	15.9	21.5
No weight fluctuation ≥ 4kgData Table Chart 4 Note †	12.1	9.8	14.8
Poor or fair general health
1+ weight fluctuation ≥ 4kg	31.6Note ***	28.7	34.6
No weight fluctuation ≥ 4kgData Table Chart 4 Note †	24.1	21.4	27.0
Pain that prevents activity (HUI)
1+ weight fluctuation ≥ 4kg	5.8Note *	4.4	7.6
No weight fluctuation ≥ 4kgData Table Chart 4 Note †	3.0	1.9	4.5
Moderate or severe disability (HUI)
1+ weight fluctuation ≥ 4kg	13.1Note ***	11.3	15.0
No weight fluctuation ≥ 4kgData Table Chart 4 Note †	8.1	6.3	10.3
Arthritis or rheumatism
1+ weight fluctuation ≥ 4kg	20.0Note *	18.0	22.1
No weight fluctuation ≥ 4kgData Table Chart 4 Note †	16.0	13.8	18.5
High cholesterol
1+ weight fluctuation ≥ 4kg	20.7	18.9	22.5
No weight fluctuation ≥ 4kgData Table Chart 4 Note †	19.3	16.2	22.8
Hypertension
1+ weight fluctuation ≥ 4kg	27.1	24.3	30.1
No weight fluctuation ≥ 4kgData Table Chart 4 Note †	24.4	21.8	27.2
Type 2 diabetes
1+ weight fluctuation ≥ 4kg	5.4	4.1	7.0
No weight fluctuation ≥ 4kgData Table Chart 4 Note †	3.8	2.7	5.3
Cardiovascular diseaseData Table Chart 4 Note 2
1+ weight fluctuation ≥ 4kg	7.6	6.2	9.2
No weight fluctuation ≥ 4kgData Table Chart 4 Note †	6.3	5.0	7.8
Obesity-related chronic conditionData Table Chart 4 Note 1
1+ weight fluctuation ≥ 4kg	59.3	56.1	62.3
No weight fluctuation ≥ 4kgData Table Chart 4 Note †	55.2	51.5	58.8
Note * significantly different from reference category (p < 0.05) Return to note * referrer Note *** significantly different to reference category (p < 0.001) Return to note *** referrer Note † reference category Return to note † referrer Note 1 Includes respondents who reported having one or more of: fibromyalgia, arthritis or rheumatism, back problems, hypertension, high cholesterol, type 2 diabetes, heart disease, had a heart attack, cancer (present or past), suffering from the effects of a stroke, kidney dysfunction or disease, liver or gallbladder problems. Return to note 1 referrer Note 2 Includes respondents who reported having heart disease, having had a heart attack or suffering from the effects of a stroke. Return to note 2 referrer Note: HUI: Health Utility Index. Source: 2007 to 2009, 2009 to 2011 Canadian Health Measures Survey, combined.

Description of Chart 5



Data Table Chart 5
Table summary
This table displays the results of Data Table Chart 5 Percentage and 95% confidence interval, calculated using from and to units of measure (appearing as column headers).

	Percentage	95% confidence interval
		from	to
Poor or fair mental health
Difference between the highest and lowest BMI ≥ 6.8kg/m2	6.2Note *	4.8	8.0
Difference between the highest and lowest BMI < 6.8 kg/m2Data Table Chart 5 Note †	3.9	3.0	5.2
Poor or fair general health
Difference between the highest and lowest BMI ≥ 6.8kg/m2	15.9Note ***	13.7	18.3
Difference between the highest and lowest BMI < 6.8 kg/m2Data Table Chart 5 Note †	7.3	6.2	8.4
Pain that prevents activity (HUI)
Difference between the highest and lowest BMI ≥ 6.8kg/m2	22.4Note ***	19.2	25.9
Difference between the highest and lowest BMI < 6.8 kg/m2Data Table Chart 5 Note †	10.8	9.2	12.8
Moderate or severe disability (HUI)
Difference between the highest and lowest BMI ≥ 6.8kg/m2	35.5Note ***	32.0	39.3
Difference between the highest and lowest BMI < 6.8 kg/m2Data Table Chart 5 Note †	24.1	21.6	26.8
Arthritis or rheumatism
Difference between the highest and lowest BMI ≥ 6.8kg/m2	24.6Note ***	22.5	26.9
Difference between the highest and lowest BMI < 6.8 kg/m2Data Table Chart 5 Note †	13.5	11.7	15.6
High cholesterol
Difference between the highest and lowest BMI ≥ 6.8kg/m2	32.6Note ***	29.5	35.7
Difference between the highest and lowest BMI < 6.8 kg/m2Data Table Chart 5 Note †	19.3	17.1	21.8
Hypertension
Difference between the highest and lowest BMI ≥ 6.8kg/m2	28.9Note ***	26.2	31.7
Difference between the highest and lowest BMI < 6.8 kg/m2Data Table Chart 5 Note †	12.6	10.7	14.7
Type 2 diabetes
Difference between the highest and lowest BMI ≥ 6.8kg/m2	8.8Note ***	7.5	10.2
Difference between the highest and lowest BMI < 6.8 kg/m2Data Table Chart 5 Note †	1.6	1.2	2.2
Cardiovascular diseaseData Table Chart 5 Note 2
Difference between the highest and lowest BMI ≥ 6.8kg/m2	9.6Note ***	8.0	11.4
Difference between the highest and lowest BMI < 6.8 kg/m2Data Table Chart 5 Note †	4.8	4.1	5.6
Obesity-related chronic conditionData Table Chart 5 Note 1
Difference between the highest and lowest BMI ≥ 6.8kg/m2	67.7Note ***	63.8	71.3
Difference between the highest and lowest BMI < 6.8 kg/m2Data Table Chart 5 Note †	48.0	45.7	50.2
Note * significantly different to reference category (p < 0.05) Return to note * referrer Note *** significantly different to reference category (p < 0.001) Return to note *** referrer Note † reference category Return to note † referrer Note 1 Includes respondents who reported having one or more of: fibromyalgia, arthritis or rheumatism, back problems, hypertension, high cholesterol, type 2 diabetes, heart disease, had a heart attack, cancer (present or past), suffering from the effects of a stroke, kidney dysfunction or disease, liver or gallbladder problems. Return to note 1 referrer Note 2 Includes respondents who reported having heart disease, having had a heart attack or suffering from the effects of a stroke. Return to note 2 referrer Note: HUI: Health Utility Index. Source: 2007 to 2009, 2009 to 2011 Canadian Health Measures Survey, combined.

Logistic regression models

Figure 1 shows that the odds of having a range of different health outcomes were higher among those with a history of obesity, who reported at least one large weight fluctuation during adulthood, or who reported a 6.8 kg/m² or higher gap between the highest and lowest adulthood BMI. In general, there were higher odds of reporting a negative health outcome among those who had obesity at the time of the survey and a history of having obesity compared with those who did not have obesity at the time of the survey but did have a history of obesity. Relative to never having obesity, having obesity in the past but not at present or having obesity in the past and at present were associated with increased odds of having a range of chronic conditions with the highest odds observed for type 2 diabetes (OR = 3.26, 95% CI: 2.40 to 4.43 and OR = 5.36, 95% CI: 3.88 to 7.41), hypertension (OR = 2.41, 95% CI: 1.69 to 3.44 and OR = 3.76, 95% CI: 2.84 to 4.97), and poor or fair self-rated general health (OR = 2.04, 95% CI: 1.51 to 2.76 and OR = 2.68, 95% CI: 2.11 to 3.40). When examined separately by age group, the odds of having an obesity-related chronic condition increased with age (Figure 2), a finding that was consistent across all health outcomes (data only shown for the clustered obesity-related chronic conditions variable).

Description of Figure 1



Data table for Figure 1
Table summary
This table displays the results of Data table for Figure 1. The information is grouped by Obesity history variables / Health outcomes (appearing as row headers), Odds
ratio and 95% Confidence interval, calculated using lower limit and upper limit units of measure (appearing as column headers).

Obesity history variables / Health outcomes	Odds ratio	95% Confidence interval
		lower limit	upper limit
Change in BMI during adulthood ≥ 6.8 kg/m2 (compared with < 6.8 kg/m2)
One or more chronic conditions	1.92	1.58	2.33
Cardiovascular disease	1.68	1.25	2.25
Hypertension	2.49	1.97	3.15
Type 2 diabetes	4.75	3.36	6.70
High cholesterol	1.83	1.52	2.20
Arthritis	1.61	1.30	2.00
Moderate-to-severe disability (HUI)	1.58	1.24	2.00
Experiences pain that prevents activity (HUI)	2.22	1.69	2.91
Poor or fair general health	2.17	1.74	2.69
Poor or fair mental health	1.64	1.12	2.41
One or more weight fluctuations (≥ 4kg) (compared with no major weight fluctuations)
One or more chronic conditions	1.47	1.18	1.83
Cardiovascular disease	1.67	1.23	2.27
Hypertension	1.33	0.99	1.79
Type 2 diabetes	1.89	1.22	2.91
High cholesterol	1.39	1.10	1.75
Arthritis	1.58	1.28	1.96
Moderate-to-severe disability (HUI)	1.45	1.21	1.75
Experiences pain that prevents activity (HUI)	1.65	1.20	2.26
Poor or fair general health	1.81	1.33	2.45
Poor or fair mental health	1.89	1.14	3.12
Currently does not have obesity with history of obesity (compared with never having obesity)
One or more chronic conditions	1.77	1.32	2.37
Cardiovascular disease	1.79	1.27	2.50
Hypertension	2.41	1.69	3.44
Type 2 diabetes	3.26	2.40	4.43
High cholesterol	1.70	1.41	2.05
Arthritis	1.36	1.00	1.83
Moderate-to-severe disability (HUI)	1.41	1.04	1.91
Experiences pain that prevents activity (HUI)	1.72	1.28	2.32
Poor or fair general health	2.04	1.51	2.76
Poor or fair mental health	1.66	0.79	3.50
Currently has obesity with history of obesity (compared with never having obesity)
One or more chronic conditions	2.46	1.84	3.29
Cardiovascular disease	2.03	1.39	2.98
Hypertension	3.76	2.84	4.97
Type 2 diabetes	5.36	3.88	7.41
High cholesterol	1.82	1.40	2.35
Arthritis	2.28	1.78	2.92
Moderate-to-severe disability (HUI)	1.87	1.51	2.33
Experiences pain that prevents activity (HUI)	2.68	2.02	3.57
Poor or fair general health	2.68	2.11	3.40
Poor or fair mental health	1.15	0.77	1.72
Notes: Dotted line is located at 1.0. BMI: body mass index. HUI: Health Utility Index. All models adjusted for age group, sex, education, marital status, income, physical activity, sedentary behaviour, diet quality, alcohol drinker type, and smoking status. Source: 2007 to 2009, 2009 to 2011 Canadian Health Measures Survey, combined.

Description of Figure 2



Data table for Figure 2
Table summary
This table displays the results of Data table for Figure 2 . The information is grouped by Obesity history variables / Age groups (appearing as row headers), Odds
Ratio and 95% Confidence interval, calculated using lower limit and upper limit units of measure (appearing as column headers).

Obesity history variables / Age groups	Odds Ratio	95% Confidence interval
		lower limit	upper limit
Currently does not have obesity with history of obesity (compared with never having obesity)
60 to 79 years	2.10	1.11	3.96
50 to 59 years	3.55	1.92	6.57
40 to 49 years	1.17	0.66	2.07
28 to 39 years	1.58	0.88	2.83
Currently has obesity with history of obesity (compared with never having obesity)
60 to 79 years	3.82	1.84	7.94
50 to 59 years	3.85	2.25	6.6
40 to 49 years	2.29	1.43	3.66
28 to 39 years	1.75	1.05	2.91
One or more weight fluctuations (≥4kg) (compared with no major weight fluctuations)
60 to 79 years	2.31	1.38	3.87
50 to 59 years	1.98	1.26	3.13
40 to 49 years	1.04	0.68	1.59
28 to 39 years	1.30	0.93	1.81
Change in BMI during adulthood ≥ 6.8 kg/m2 (compared with < 6.8 kg/m2)
60 to 79 years	2.67	1.75	4.08
50 to 59 years	2.58	1.77	3.74
40 to 49 years	1.73	1.22	2.46
28 to 39 years	1.42	0.93	2.17
Notes: Dotted line is located at 1.0. BMI: body mass index. All models adjusted for age group, sex, education, marital status, income, physical activity, sedentary behaviour, diet quality, alcohol drinker type, and smoking status. Source: 2007 to 2009, 2009 to 2011 Canadian Health Measures Survey, combined.

Discussion

Obesity at a single time point does not tell the complete story of one’s risk for chronic disease and mortality. Most individuals with obesity exhibit evidence of metabolic dysfunction and CVD risk,^Note 20 while others exhibit few (if any) markers of CVD risk.^Note 21, ^Note 22 This heterogeneity in CVD risk among individuals with obesity is dependent on a myriad of factors; however, one factor that is often overlooked is the length of time people have had obesity.^Note 23 Obesity is occurring earlier in the life course,^Note 24 thus increasing the potential for longer and earlier exposure to obesity. The ideal approach to examine the impact of the length and timing of obesity exposure on health is a prospective cohort that tracks obesity status and health over a long period. In the absence of such a data source, the present study used retrospective weight history information gathered via a questionnaire to examine whether a relationship emerged between past and current obesity status with current health. This study found that having obesity in the past, regardless of current obesity status, was associated with increased odds of poor health outcomes. Further, having obesity at the time of the survey and at least once in the past was associated with even poorer health.

The present study found that increased exposure to obesity during adulthood was associated with an increased odds of a series of negative health outcomes, except for poor or fair mental health, even if the obesity had resolved. Similarly, having a larger gap between one’s lowest and highest adulthood BMI or having experienced 1 or more major weight fluctuations (greater than 4 kg (10 lb.) in 1 year) were associated with increased odds of negative outcomes. Other studies that used the same weight change module as in the CHMS found an association between weight history variables and CVD risk, asthma, hypertension and mortality.^Note 12, ^Note 13, ^Note 14 One study that also used a retrospective weight history recall approach reported that gaining 11 lb. from early to middle adulthood (i.e., age 18 to 21 years to age 55 years) was associated with a 30% increase in risk of type 2 diabetes, 14% increase in risk of hypertension and 8% increased risk of CVD.^Note 5 Using data from the National Health and Nutritional Examination Survey in the United States, Stokes and colleagues reported that for each of the eight diseases they examined, prevalence was higher among those that had obesity in the past than among those who never had obesity.^Note 25

The present study found that having one or more large weight fluctuations was associated with higher odds of experiencing any of the negative health outcomes examined, including poor or fair mental health. Previous research has reported that 20% of overweight and obese individuals who lose weight maintain their weight loss,^Note 26 while the majority often return to or surpass their pre-intervention weight within 2 to 5 years.^Note 27 The Endocrine Society’s Scientific Statement on obesity pathogenesis pinpoints that weight regain or fluctuations happen because once weight loss occurs, the body decreases energy expenditure at rest and during exercise while hunger increases.^Note 28 This pattern is problematic given the known association between weight fluctuations and negative health outcomes.^Note 29, ^Note 30 Moreover, the timing of weight fluctuations appears to be important given that weight fluctuations in early to mid adulthood are more likely to be associated with negative health outcomes compared with weight fluctuations later in life.^Note 31 The present study could not examine the timing of weight fluctuations but does support the relationship between weight fluctuations and poor health.

The risk of morbidity and mortality inevitably increases with age, therefore analyses like the present one must consider possible age-related variations in results. When logistic regression models were fit separately by age group, the overall story did not appreciably change compared with the overall results. However, there was evidence of increasing odds of having obesity-related chronic conditions as age increased. This finding suggests that a history of obesity, regardless of when it occurs in adulthood, does increase one’s risk of disease. Further, a history of obesity combined with an older age further increases that risk. Ideally, a dataset would include weight information collected prospectively at several time points throughout adulthood to further disentangle how the length of time exposed to and the timing of obesity affect one’s risk. This approach is not possible with the data currently available in the CHMS.

Given the breadth of adult ages (18 to 79 years) included in the CHMS, the present study shows some observations regarding generational differences in weight at age 25. Respondents aged 70 to 79 years at the time of the survey (i.e., from 2007 to 2011), reported lower average weight at age 25 compared with adults aged 28 to 39 years at the time of the survey. This finding makes sense if one considers that those aged 70 to 79 between 2007 and 2011 had been aged 25 years at one point between 1953 and 1966 (a time when the prevalence of obesity [i.e., BMI greater than 30.0 kg/m²] in Canada was less than 10%^Note 32), while those aged 28 to 39 years between 2007 and 2011 were aged 25 years at one point between 1993 and 2008 (a time when the prevalence of obesity in Canada was about 25%)2 and the environment was more obesogenic.^Note 33 The present study also shows that the lowest adulthood weight was higher among the youngest generation compared with the older one. Furthermore, the average age when body weight was lowest was lower among the youngest age group compared with the oldest. Both findings suggest that the upward shift in weight is occurring earlier in life. A comparison of Gen X women (born between 1973 and 1978) and millennial women (born between 1989 and 1995) observed that millennial women were 4 kg heavier at ages 18 to 23 and gained weight 1.7 times faster than Gen X women.^Note 34 This study also projected that millennial women will be, on average, 16.7 kg heavier (average weight 93.2 kg) at age 41 than Gen X women (average weight 76.5 kg). In another generational obesity study, Zheng and colleagues compared the original cohort of the Framingham Heart Study (started in 1948) with an offspring cohort (started in 1971) and showed that BMI trajectories shifted upwards earlier among the offspring cohort compared with the original older generation.^Note 35 In the present study, the amount of weight gain (i.e., difference in weight from 10 years ago to the time of the survey) was higher among the youngest age group (28 to 39 years) (Chart 2). This finding is consistent with previous research that reported young adults are gaining weight faster than any other age group.^Note 36 The health complications of obesity being observed today among older adults will likely only become poorer given that younger cohorts are having obesity earlier and are gaining weight at a faster rate than older generations.^Note 24

Limitations

Important limitations of the present study must be noted. It is possible that historical weight information was not reported accurately. It is also possible that the accuracy of reporting one’s weight at age 25 becomes more difficult the further one is from age 25.^Note 11 It is important to note that contextual information that may explain a weight fluctuation (e.g., health condition) is not available in the survey and thus limits a full understanding of the results. It is possible that estimates of obesity at all time points are underestimated given that self-reported weight tends to be lower than measured weight, in particular among women.^Note 37, ^Note 38 The three weight history variables (i.e., never having obesity, currently not having obesity but having obesity in the past, and currently having obesity and having had obesity in the past) may have missed periods of obesity in one’s history. Respondents were asked to report their weight at present, 1 year ago, 10 years ago and at age 25. They may have had obesity at another time outside these time points, and this would not be captured by the survey. Given the variability in baseline age, it was not possible to create a variable that accurately captures the length of time exposed to obesity nor was it appropriate to assume a person who reported having obesity at two different time points in fact had obesity the entire time in between. The definition of weight fluctuation used in the questionnaire module is in absolute terms (4 kg, 10 lb.) and thus may have differing impacts on people depending on their height. Prospective cohort studies on large samples would allow for a more detailed examination of how timing and length of exposure to obesity are related to health. As with any cross-sectional analysis, causality cannot be inferred from these results. Finally, the data were collected over a decade ago, and the weight change module was not included in more recent cycles of the CHMS. While the age of the data is not ideal, the focus of the present analysis was on the associations between weight history and health rather than on temporal trends in obesity.

Conclusions

The findings of the present study add to a growing body of evidence that one’s risk for disease and mortality increases as the number of years lived with obesity increases^Note 39 and a dynamic measure that captures changes in BMI across the life course is more predictive of disease and mortality than one’s obesity status at a single point in time.^Note 35 In other words, the population burden of obesity should consider not only those who currently have obesity, but also those who have ever had obesity in their lifetime.^Note 25 These findings align with recent calls to add obesity history to routine health surveillance^Note 25 and update clinical practice guidelines so that obesity history, maximum lifetime BMI and timing of obesity onset are included in the medical history of patients presenting with obesity.^Note 40 Generational shifts in obesity trajectories suggest that the population burden of obesity is likely to increase over time.