Health at a Glance
Aerobic fitness, body mass index and health-related risk factors

by Janine Clarke and Shirley Bryan

Release date: March 28, 2017

Highlights

  • Health-related risk factors (such as high blood pressure or a large waist circumference) were more common among adults who have aerobic fitness ratings of needs improvement or fair compared with adults who have good, very good or excellent aerobic fitness.
  • The presence of one or more health-related risk factor was less likely among adults with good, very good or excellent aerobic fitness compared with their less fit counterparts, even among those who were overweight or obese.
  • Large waist circumference was the health-related risk factor that showed the largest differences across aerobic fitness ratings, particularly among overweight and obese adults.

Introduction

Physical fitness plays an important role in improving health and well-being. There are several components of physical fitness, including aerobic fitness and body composition. Aerobic fitness—referring to the ability of the lungs, heart and circulatory system to efficiently deliver oxygen to working muscles for use during physical activity—benefits many parts of the body, including the heart, lungs, muscles, bones, blood, immune system and nervous system.Note 1 In relation to health disorders, a high level of aerobic fitness reduces the risk for such conditions as type 2 diabetes, cardiovascular disease, hypertension, cancer, and osteoporosis.Note 2Note 3Note 4Note 5 There are also benefits to mental health, including a reduced risk for depression.Note 2Note 3Note 4Note 5 As well, people at higher levels of aerobic fitness, compared with those at lower levels, have a reduced risk of premature death from all causes.Note 5Note 6

Body composition, or more specifically excess body fat (i.e., overweight or obesity), is also associated with an increased risk for conditions such as type 2 diabetes, cardiovascular disease, hypertension, cancer, and osteoporosis, as well as an increased risk of premature death.Note 7 However, it has been shown that a high level of aerobic fitness can reduce some of the health risks associated with overweight and obesity.Note 6Note 8Note 9

This article explores the percentage of adults aged 20 to 59 with various health-related risk factors according to aerobic fitness rating (as measured by a fitness test called the modified Canadian Aerobic Fitness Test or mCAFT). Specifically, the percentage of adults with selected health-related risk factors is reported by aerobic fitness rating (needs improvement or fair, good, very good or excellent). The risk factors examined include high blood pressure, large waist circumference, high triglyceride levels (a type of fat), low high density lipoprotein levels (“good” cholesterol) and high blood sugar. The risk factors were selected on the basis of their relationship to metabolic syndrome—defined as a constellation (or clustering) of at least three of the risk factors. Metabolic syndrome, which is present in about one-fifth of Canadian adults,Note 10 is associated with an increased risk of cardiovascular disease and type 2 diabetes.Note 11

As a second part of the analysis, adults aged 20 to 59 were classified as either having one or more of the five health-related risk factors mentioned above, or having no risk factors. The percentage of adults classified as having one or more health-related risk factor is presented by aerobic fitness rating and body mass index (BMI) category (normal weight, overweight, obese). Overweight (defined as a body mass index, or BMI, of 25 to 29.9 kg/m2) and obesity (BMI of 30 kg/m2 or higher) is an important public health issue in Canada—recent estimates suggest that nearly two out of every three Canadian adults is overweight or obese.Note 12

Data for this article are from the combined 2007 to 2011 Canadian Health Measures Survey.

About physical activity

Physical activity and physical fitness are terms that are often used interchangeably. Although related, they are not the same. Physical activity refers to any movement or action that increases the heart rate and rate of breathing. In the context of health, physical fitness is defined as “the ability to carry out daily tasks with vigor and alertness, without undue fatigue, and with ample energy to enjoy leisure-time pursuits and to meet unforeseen emergencies.”Note 1 Physical fitness, including aerobic fitness and body composition, is improved and maintained through regular participation in physical activity.

Physical activity of at least moderate intensity appears to be required for beneficial effects on healthNote 13 while improvements to aerobic fitness are realized when physical activity is pursued at a more vigorous level.Note 14 Canada’s Physical Activity Guidelines recommend that adults participate in activities of moderate-to-vigorous intensity for at least 150 minutes each week.Note 15

An activity is considered moderate or vigorous based on how hard you are working to carry out that activity and how much energy you are using to do it. The following guidelines can help determine whether an activity is moderate or vigorous:

Moderate-intensity physical activities are those where you are working hard enough to raise your heart rate but you can still talk, but not sing your favourite song, during the activity.Note 15

Vigorous-intensity physical activities are those that make your heart rate go up quite a bit. During these activities you will not be able to say more than a few words without pausing for a breath.Note 15

Recent results show that very few Canadian adults are considered physically active according to Canada’s Physical Activity Guidelines—one in five Canadian adults aged 18 to 79 achieved the recommended level of physical activity each week.Note 16

Health-related risk factors are less common among adults with better aerobic fitness ratings

Description for Chart 1
Chart 1
Percentage of Canadians aged 20 to 59 with selected health-related risk factors, by aerobic fitness rating
Table summary
This table displays the results of Percentage of Canadians aged 20 to 59 with selected health-related risk factors. The information is grouped by Health-related risk factor (appearing as row headers), Needs improvement or fair, Good and Very good or excellent, calculated using percent units of measure (appearing as column headers).
Health-related risk factor Needs improvement or fairChart 1 Note  Good Very good or excellent
percent
Large waist circumference 50.2 14.4Note * 3.8Note E: Use with cautionNote *
High blood pressure 16.6 10.3Note E: Use with cautionNote * 6.7Note E: Use with cautionNote *
High triglycerides 33.2 17.8Note * 11.0Note *
Low 'good' cholesterol 39.1 23.7Note * 19.7Note *
High blood sugar 9.4 4.5Note E: Use with cautionNote * 3.6Note E: Use with cautionNote *

In Canadian adults aged 20 to 59, each of the five health-related risk factors were much less common among those with good, very good or excellent aerobic fitness compared to those with a fitness rating of needs improvement or fair (Chart 1). In fact, for each health-related risk factor examined, the percentage of adults with a given risk factor was at least 40% lower among those with good aerobic fitness and at least 50% lower among those with very good or excellent aerobic fitness, compared to those with an aerobic fitness rating of needs improvement or fair. This is consistent with evidence suggesting that higher levels of physical activity and physical fitness are associated with a lower percentage of adults with metabolic syndrome and its risk factors.Note 17Note 18

The greatest difference observed across aerobic fitness ratings was for large waist circumference. That is, 50% of those with a fitness rating of needs improvement or fair had a large waist circumference, more than triple the percentage of those with good aerobic fitness (14%) and just over 12 times the percentage of those with very good or excellent fitness (4%). The relationship between aerobic fitness and large waist circumference is discussed in more detail later in this article.

Presence of one or more health-related risk factor was less common among adults with very good or excellent aerobic fitness regardless of obesity status

In each BMI category, the likelihood of having one or more health-related risk factors was significantly lower among adults with very good or excellent aerobic fitness compared with adults with an aerobic fitness rating of needs improvement or fair (Chart 2). Similarly, in those classified as overweight and who had a good aerobic fitness rating, the percentage with at least one health-related risk factor was significantly lower than in those who were overweight but had an aerobic fitness rating of needs improvement or fair. These results are consistent with research showing a lower risk of developing metabolic syndrome among adults with high aerobic fitness levels, even in those who were overweight or obese.Note 8

Description for Chart 2
Chart 2
Percentage of Canadians aged 20 to 59 with one or more health-related risk factor, by body mass index (normal weight, overweight, obese)Chart 2 Note 1 and aerobic fitness rating (needs improvement or fair, good, very good or excellent)
Table summary
This table displays the results of Percentage of Canadians aged 20 to 59 with one or more health-related risk factor. The information is grouped by Body mass index and aerobic fitness rating
(appearing as row headers), Percent (appearing as column headers).
Body mass index and aerobic fitness rating
Percent
Normal weight  
NI/FChart 2 Note  35.1
G 27.9
VG/Ex 24.6Note *
Overweight  
NI/FChart 2 Note  75.7
G 59.3Note *
VG/Ex 44.4Note *
Obese  
NI/FChart 2 Note  97.0
G 88.2
VG/Ex 51.0Note E: Use with cautionNote *

One way that aerobic fitness is thought to be related to health among people who are overweight or obese is due to the effect of regular physical activity on excess body fat, particularly in the abdominal area. Excess abdominal fat is associated with an increased risk of type 2 diabetes, coronary heart disease and hypertension.Note 19Note 20Note 21 As we saw above, a large waist circumference was the risk factor that was most significantly influenced by aerobic fitness rating. Chart 3 looks at large waist circumference (≥ 102 cm for males or ≥ 88 cm for females) by BMI and aerobic fitness rating. It shows that even among overweight and obese adults, the percentage with large waist circumference was significantly lower for those with good, very good or excellentNote 22 aerobic fitness compared to those with an aerobic fitness rating of needs improvement or fair. This is consistent with several studies reporting that an increase in physical activity and aerobic fitness resulted in a decrease in abdominal fat, even without overall weight loss or a change in BMI category.Note 8Note 23Note 24 A decrease in body fat can have a positive influence on overall health and significantly reduce the risk of disease and death.Note 8Note 23Note 24

Description for Chart 3
Chart 3
Percentage of Canadians aged 20 to 59 with large waist circumference,Chart 3 Note 1 by body mass indexChart 3 Note 2 and aerobic fitness rating (needs improvement or fair, good, very good or excellent)
Table summary
This table displays the results of Percentage of Canadians aged 20 to 59 with large waist circumference. The information is grouped by Body mass index and aerobic fitness rating
(appearing as row headers), Percent (appearing as column headers).
Body mass index and aerobic fitness rating
Percent
Overweight  
NI/FChart 3 Note  40.7
G/VG/Ex 15.8Note *
Obese  
NI/FChart 3 Note  92.8
G/VG/Ex 57.8Note *

Conclusion

This study shows that in adults aged 20 to 59 with an aerobic fitness rating of good, very good or excellent, the percentage with selected health-related risk factors was lower than in their less fit counterparts. While the benefit of higher aerobic fitness was observed for blood pressure, triglyceride, cholesterol and blood sugar levels, the difference was greatest for large waist circumference, which may reflect the influence of physical activity and aerobic fitness on excess body fat, specifically abdominal fat. The analysis also shows that even among adults classified as overweight or obese, aerobic fitness is related to a lower likelihood of having one or more risk factors. These findings underscore the importance of aerobic fitness in lowering the risk of chronic conditions such as metabolic syndrome, type 2 diabetes, coronary heart disease and hypertension and thus may be useful in informing policy and programming aimed at improving the health of Canadians.

Data source, methods and definitions

Data source

The Canadian Health Measures Survey (CHMS) is a cross-sectional survey conducted by Statistics Canada in partnership with Health Canada and the Public Health Agency of Canada. Data were collected over a two-year collection cycle from a nationally representative sample of Canadians aged 6 to 79 in cycle 1 (March 2007 to February 2009) and 3 to 79 in cycle 2 (August 2009 to November 2011). The results are representative of approximately 96% of the Canadian population with the following exclusions: persons living on reserves or other Aboriginal settlements, full-time members of the Canadian Forces, institutionalized populations, and persons living in certain remote regions. The CHMS includes an in-home interview and a visit to a mobile clinic where physical measurements (e.g., height and weight) and blood and urine samples are taken.

Methods

For this study, data from cycles 1 and 2 of the CHMS were combined to increase the sample size. Respondents were included (n = 3,845) if they were 20 to 59 years of age and had valid results for each of the following tests or measurements: aerobic fitness, body mass index (BMI), and five health-related risk factors. Each are described in more detail below.

The aerobic fitness rating was determined from a submaximal exercise test called the modified Canadian Aerobic Fitness test (mCAFT).Note 1Note 12Note 25Note 26 The mCAFT is a moderate intensity exercise test that was performed by the respondents at the CHMS clinic. During the test the respondent’s heart rate was monitored while they stepped up and down a set of stairs continuously to music during a series of three minute stages. The heart rate at the end of the last completed stage of stepping was used to calculate the respondent’s aerobic fitness score. The score is then used to assign, based on their age and sex, one of the following aerobic fitness ratings:

  • needs improvement
  • fair
  • good
  • very good
  • excellent

Due to small sample sizes in this study, the aerobic fitness ratings were regrouped into three categories as follows: needs improvement/fair, good, and very good/excellent.

Body mass index (BMI) was directly measured in the CHMS clinic following standard procedures.Note 25Note 26 It was calculated by dividing a person’s weight in kilograms (kg) by their height, squared, in metres (m2). For non-pregnant adults ages 18 and older, BMI was categorized according to cut-points recommended by Health CanadaNote 19 and the World Health OrganizationNote 27 as follows:

  • normal weight (18.5 to 24.9 kg/m2)
  • overweight (25.0 to 29.9 kg/m2)
  • obese (30.0 kg/m2 and over)

When interpreting BMI, it is important to note that it is not a direct measure of body fat. As a result, misclassification can occur among those with higher levels of fat-free mass (e.g., muscle, bone). For example, a person who is particularly muscular (and therefore has a high fat-free mass) might be categorized as overweight based on their BMI. However, this person’s actual health risk would be lower than someone with the same BMI who has a higher fat mass.Note 19

The health-related risk factors included in this analysis were directly measured at the CHMS clinic and include large waist circumference, high blood pressure, high triglycerides, low high-density lipoprotein (HDL) cholesterol and high blood sugar (determined from blood glucose levels for fasted respondents or from glycated hemoglobin A1c from non-fasted respondents). Using the cut-offs outlined in Table 1, respondents were classified as having at least one risk factor or having no risk factors.Note 11

Table 1 Cut-offs for the health-related risk factors examined in this article
Table summary
This table displays the results of Table 1 Cut-offs for the health-related risk factors examined in this article Cut-off (appearing as column headers).
  Cut-offTable 1 Note 1
Risk factor Males Females
Large waist circumference ≥ 102 cm ≥ 88 cm
High blood pressure ≥130/85 mmHg ≥130/85 mmHg
High triglyceridesTable 1 Note 2Table 1 Note 3 ≥ 1.7 mmol/L ≥ 1.7 mmol/L
Low high-density lipoprotein cholesterolTable 1 Note 4 < 1.03 mmol/L < 1.3 mmol/L
High blood sugarTable 1 Note 5    
Glucose ≥ 5.6 mmol/L ≥ 5.6 mmol/L
Glycated hemoglobin A1c (HbA1c) ≥ 6.5 % ≥ 6.5 %

Definitions

Glucose is a type of sugar in the blood used as a source of energy for all body organs and functions.

Glycated hemoglobin A1c (or HbA1c) is an indicator of the average levels of sugar in the blood during the previous two to three months.

High-density lipoprotein (HDL) cholesterol is known as “good cholesterol” because it helps to remove cholesterol from the blood vessels for breakdown and disposal, preventing fatty build up.

Metabolic syndrome is a condition that increases a person’s relative risk of cardiovascular diseases and type 2 diabetes. Metabolic syndrome is present when a person has 3 or more of the health-related risk factors discussed in this article.Note 11

Triglycerides are a type of fat that the body uses to produce energy. They are the form in which most fat is stored in the body.

Janine Clarke and Shirley Bryan are analysts with the Health Statistics Division at Statistics Canada.

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Related material for this article

Additional information

For more statistics and analysis on the health of Canadians and the health care system, visit the Health in Canada module. This module is accessible from the Statistics Canada website, under Features.

Related tables

CANSIM Table 117-0007 Distribution of the household population by musculoskeletal fitness classification, by sex and age group
CANSIM Table 117-0005 Distribution of the household population by adult body mass index (BMI) – Health Canada (HC) classification, by sex and age group

Related articles

Aerobic fitness of Canadians, 2009 to 2011
Body composition of adults, 2012 and 2013
Metabolic syndrome in adults, 2012 and 2013

Data sources

Canadian Health Measure Survey (CHMS)

How to cite this article

Clarke, J. and S. Bryan. 2017. "Aerobic fitness, body mass index and health-related risk factors." Health at a Glance. Statistics Canada Catalogue no. 82-624-X.

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