Scottish Health Survey 2017 - volume one: main report
Presents results for the Scottish Health Survey 2017, providing information on the health and factors relating to health of people living in Scotland.
8. Obesity
Diana Bardsley
Summary
- Around two thirds (65%) of adults were overweight or obese (BMI of 25 kg/m² or greater). This has remained stable since 2008 (fluctuating between 64% and 65%).
- Levels of obesity, including morbid obesity (BMI of 30 kg/m² or greater), among all adults remained at 29%, unchanged since 2015. This is significantly higher than in 2003 (24%).
- In 2016/2017, the proportion of men and women with a raised waist circumference (men: larger than 102 cm, women: larger than 88cm) had increased since 2003. For women the increase was more profound, from 39% in 2003 to 54% in 2016/2017 (an increase of 16 percentage points), whereas for men the increase was from 28% in 2003 to 38% in 2016/2017 (an increase of 10 percentage points).
- Health risk based on BMI and waist circumference increased with age for both men and women.
- Prevalence of children at risk of obesity in 2017 was 13%, with levels showing a steady decline since 2014 (16-17% between 2003 and 2014), this is largely due to the decline in prevalence among boys from 20% in 2012 to 12% in 2017.
- In 2017, the proportion of children of a healthy weight decreased with age; with children aged 2-6 being the most likely to fall within the healthy weight range (78%), compared with 66% of children aged 12-15.
8.1 Introduction
Worldwide obesity has nearly tripled since 1975. In 2016, 39% of adults aged 18 and over across the world were overweight, with 13% considered obese. Once considered a high-income country problem, overweight and obesity are now also on the rise in low and middle-income countries. Globally, there are more people who are obese than are underweight, and the majority of the world's population live in countries where overweight and obesity kills more people than underweight[1].
Overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health[1],[2]. Raised BMI is a major risk factor for non-communicable diseases such as cardiovascular disease, diabetes, musculoskeletal disorders and a range of cancers[1]. Obesity has been found to be the second biggest preventable cause of cancer[3]. There is also evidence suggesting a link between overweight and obesity in midlife and dementia in late life[4],[5],[6].
The impact of overweight and obesity upon quality of life and health is felt across the life course. Childhood obesity is associated with a higher chance of adult obesity as well as premature death, disability, diabetes, cardiovascular disease, osteoarthritis and some cancers[1],[7],[8],[9]. In addition to increased future risks, obese children can experience an increased risk of fractures, hypertension, type 2 diabetes, asthma as well as negative psychological effects during the childhood years[1],[10],[11].
Scotland has one of the worst obesity records among OECD countries. Various studies have attempted to estimate the costs to the NHS in Scotland of overweight and obesity combined, with suggested figures ranging between £363 and £600 million (the majority of these costs are incurred as a result of associated conditions such as cardiovascular disease and Type 2 diabetes, rather than direct costs of treating or managing overweight and obesity). The latest estimate of the total (direct and indirect) costs of overweight and obesity to Scottish society, including labour market related costs such as lost productivity, have been put at £0.9-4.6 billion[12].
Due to the considerable individual, social, and economic consequences of obesity, it remains a key priority and a major challenge for both government and public health professionals.
8.1.1 Policy background
In July this year, the Scottish Government published A Healthier Future – Scotland's Diet and Healthy Weight Delivery Plan[13]. The overall aims of the plan are to create a Scotland 'where everyone eats well and has a healthy weight'. There is a significant emphasis on the early years with an ambition to halve childhood obesity by 2030. There is also an aim to significantly reduce health inequalities through both population measures as well as a number of targeted approaches for the most at risk families and individuals. There is recognition that overweight and obesity is a complex issue and is associated with a number of other health behaviours such as physical activity, diet and smoking. As part of a joined up approach to public health it is stated that this plan should be considered alongside A More Active Scotland: Scotland's Physical Activity Delivery Plan[14] and other strategies focussing on Alcohol Prevention, Substance Use and Tobacco Control.
Specifically there are five key outcomes in the diet and healthy weight plan:
- Children have the best start in life – they eat well and have a healthy weight
- The food environment supports healthier choices
- People have access to effective weight management services
- Leaders across all sectors promote healthy weight and diet
- Diet-related health inequalities are reduced
Reducing overweight and obesity prevalence also contributes to the new NPF outcome that 'we are healthy and active'[15]. There is a related indicator to monitor the proportion of healthy weight adults of which SHeS is the official source used to monitor progress.
The recently published Programme for Government 2017-18 also sets out the Scottish Government's intention to progress measures limiting the marketing of products high in fat, sugar and salt[16].
8.1.2 Reporting on obesity in the Scottish Health Survey (SHeS)
The anthropometric measures presented in this chapter focus on measurements relevant to adult and child obesity. Height, weight and waist measurements have been collected during the survey interview every year since its inception in 1995. SHeS is one of a small number of surveys that collects height, weight and waist measures rather than using self-reported measures, which are known to be less accurate[17],[18]. Height and weight are used to calculate Body Mass Index (BMI), the primary measure of obesity used in the SHeS series. Adults' and children's trends in BMI are examined in this chapter, as are trends in adult waist circumference and health risks categories associated with BMI and waist measurements.
Supplementary tables are available on the Scottish Government SHeS website[19].
8.1.3 Comparability with other UK statistics
Adult obesity is defined consistently in the Scottish Health Survey and the other health surveys within the UK using BMI classifications. Height and weight measurements are self-reported in the National Survey for Wales and are therefore not directly comparable with equivalent statistics in Scotland, England and Northern Ireland, where direct measurements are taken. Sampling methodologies differ between the surveys. Of the four UK health surveys, the Scottish Health Survey and Health Survey for England are the most closely aligned.
8.2 Methods and Definitions
8.2.1 Methods
Height
Height was measured using a portable stadiometer with a sliding head plate, base plate and four connecting rods marked with a metric measuring scale. Participants were asked to remove shoes. One measurement was taken, with the participant stretching to the maximum height and the head positioned in the Frankfort plane[20]. If the reading was between two millimetres it was recorded to the nearest even millimetre. No measurement was taken from participants who were pregnant, aged under 2, or unsteady on their feet.
Weight
Weight was measured using either Seca or Tanita electronic scales, both of which use a digital display. Participants were asked to remove shoes and any bulky clothing. A single measurement was recorded to the nearest 100g. A weight measurement was not collected from participants who were pregnant, aged under 2 years, or unsteady on their feet. Due to the scale limits, when using a Tanita scale those who weighed more than 130 kg were asked for an estimate of their weight, with estimates required for those weighing more than 200 kg if Seca scales were being used. These estimated weights were included in the analysis presented in this chapter.
In the analysis of height and weight, data from those who were considered by the interviewer to have unreliable measurements, for example those who had excessive clothing on, were excluded.
Waist
Since 2012, specially trained interviewers have taken waist measurements from respondents. These interviewers followed a different protocol for taking the measurements than the nurses who previously took the measurements (see below for details). Results in this chapter are calibrated to allow the comparison of interviewer measurements with those previously taken by nurses.
Waist circumference is now defined as around the navel or tummy button. Waist was measured using a tape with an insertion buckle at one end. Interviewers took each measurement twice, using the same tape, and recorded readings. If the reading fell between two millimetres the reading was taken to the nearest even millimetre. Those participants whose two waist measurements differed by more than 3 cm had a third measurement taken. The mean of the two valid measurements (the two out of the three measurements that were the closest to each other, if there were three measurements) was used in the analysis presented in this chapter. Participants were excluded if they reported that they were pregnant, had a colostomy or ileostomy, or were unable to stand. All those with measurements considered unreliable by the interviewer, for example due to excessive clothing or movement, were excluded from the analysis presented in this chapter.
8.2.2 Definitions
Body Mass Index (BMI)
Body Mass Index (BMI) is a widely accepted measure that allows for differences in weight due to height. It is defined as weight (kg)/square of height (m2). This has been used as a measure of obesity in SHeS since its inception in 1995. BMI was calculated from valid measures collected by the interviewer.
Adult BMI classification
Based on their BMI, adult participants were classified into the following groups based on the World Health Organisation (WHO) classification[21]:
| BMI (kg/m2) | Description |
|---|---|
| Less than 18.5 | Underweight |
| 18.5 to less than 25 | Normal |
| 25 to less than 30 | Overweight, excluding obese |
| 30 to less than 40 | Obese, excluding morbidly obese |
| 40+ | Morbidly obese |
In this chapter, both mean BMI and prevalence for the five categories outlined in the table above are presented for adults. Although obesity has the greatest ill-health and mortality consequences, overweight is also a major public health concern, not least because overweight people are at high risk of becoming obese. Being underweight can also have negative health consequences.
Child BMI classification
BMI is defined for children in the same way as it is for adults: weight (kg)/square of height (m2). The International Obesity Task Force concluded that BMI is a reasonable measure of adiposity in children[22] and it is the key measure of overweight and obesity for children used in the SHeS series.
Despite the relatively wide acceptance of the use of BMI as an adiposity indicator, the establishment of an agreed specific obesity and overweight classification system for children and young people remains challenging. Constant changes in body composition during growth mean that the relationship between weight-for-height and adiposity during childhood and adolescence is age-dependent, and this relationship is further complicated by both ethnicity and gender[23].
The classification of children's BMI used in this chapter, set out below, has been derived from BMI percentiles of the UK 1990 reference curves[24],[25] (referred to as the national BMI percentiles classification); these have been used in each SHeS to date. The national BMI percentiles classification has been shown to be reasonably sensitive (i.e. not classifying obese children as non-obese) and specific (i.e. not classifying non-obese children as obese)[26],[27]. SIGN recommends that these reference curves and thresholds should be used for population surveillance in Scotland. The 85th / 95th percentile cut-off points are commonly accepted thresholds used to analyse overweight and obesity in children. These thresholds have previously been used to describe childhood overweight and obesity prevalence trends in the UK[28],[29],[30],[31].
| Percentile cut-off | Description |
|---|---|
| At or below 2nd percentile | At risk of underweight |
| Above 2nd percentile and below 85th percentile | Healthy weight |
| At or above 85th percentile and below 95th percentile | At risk of overweight |
| At or above 95th percentile | At risk of obesity |
SHeS uses a method developed by ISD Scotland to plot the exact ages of the children in the sample against the reference population data[32]. While children's exact age was used to calculate the BMI grouping prevalence rates (based on the interview date and the date of birth), results are presented using grouped ages based on age at last birthday.
As noted in the introduction to this chapter, one of the Scottish Government's national indicators relates to healthy weight in both children and adults, defined as neither underweight nor overweight or obese[33]. The presented data for children have been categorised to show the total proportions that are: healthy weight, at risk of overweight, at risk of obesity, and at risk of underweight.
Raised waist circumference (WC)
BMI has some limitations and does not, for example, distinguish between mass due to body fat and mass due to muscular physique[34]. Nor does it take account of the distribution of fat in the body. It has therefore been suggested that waist circumference (WC) may be a better means of identifying those with a health risk than BMI[35],[36],[37].
In accordance with the definition of abdominal obesity used by the National Institutes of Health (USA) ATP (Adult Treatment Panel) III, a raised WC is defined as more than 102 cm for men and more than 88 cm for women[38]. Following the protocol introduced to SHeS in 2012, described in Section 8.2.1, the equivalent cut-offs on SHeS are 102.75cm for men and 91.35cm for women[39].
These thresholds help identify people at risk of metabolic syndrome. Abdominal obesity is reported as more highly correlated with metabolic risk factors (high levels of triglycerides, low HDL-cholesterol) than elevated BMI. It has recently been shown that these levels correspond fairly closely to the 95th percentile of waist circumference for healthy people, indicating that few healthy people have a waist circumference above these thresholds[40].
Combined assessment of health risk from obesity
The SIGN guideline on obesity cites the WHO's recommendation that an individual's risk of conditions such as type 2 diabetes and CVD is better estimated using a combination of both BMI and waist circumference (WC) than using either measure on their own[41].
The classification categories suggested by SIGN[42] are set out in the following table. BMI, derived from height and weight data collected in the main interview, in combination with waist measurements collected in the biological module have been used to estimate the proportion of adults who fall into each of the risk categories. This combined classification designates those with a raised WC as 'very high' WC, while those towards the upper end of the 'not raised' WC range are designated 'high' WC. As the table indicates, the health risk is similar for adults with very high WC and class I obesity and for adults with high WC and class II obesity. The SIGN guidance notes that increased WC can be a marker for disease even among people of normal weight. The analysis presented in this chapter classifies people with normal weight and a very high WC as at increased risk of disease.
Assessment of health risk from obesity
| BMI Classification | 'High' WC Men WC 94-102cm Women WC 80-88cm |
'Very high' WC Men WC >102cm Women WC >88cm |
|---|---|---|
| Normal weight (BMI 18.5 - <25(kg/m2)) | - | - |
| Overweight (BMI 25 - <30(kg/m2)) | Increased | High |
| Obese | ||
| I - Mild (BMI 30 - <35(kg/m2)) | High | Very high |
| II - Moderate (BMI 35 - <40(kg/m2)) | Very high | Very high |
| III - Extreme (BMI 40+(kg/m2)) | Extremely high | Extremely high |
Source: based on Table 3, P11, in SIGN 115[43].
8.3 Adult Overweight and Obesity Prevalence
8.3.1 Trends in overweight including obesity prevalence since 2003
Adult overweight, including obesity (BMI of 25 kg/m² or greater) prevalence remained at 65% in 2017. As shown in figure 8A, the longer trend for overweight including obesity showed a significant increase between 2003 and 2008, when prevalence increased from 62% to 65%. Since 2008, prevalence has stabilised, fluctuating between 64% and 65%.
The trend pattern in overweight, including obesity for men was similar to that of all adults. As shown in Figure 8A, prevalence of overweight, including obesity rose amongst men between 2003 and 2008 (from 65% to 68%), and has remained steady since, with 67% of men in 2017 overweight including obese.
Prevalence of overweight, including obesity among women was consistently lower over the time period than among men, ranging from 60% to 63% with no clear pattern of increase or decline.
Figure 8A, Table 8.1
8.3.2 Trends in obesity prevalence since 2003
Prevalence of obesity, including morbid obesity (BMI of 30 kg/m² or greater), among all adults remained at 29% in 2017, unchanged since 2015, although significantly higher than in 2003 (24%). A similar pattern was found for men and women.
There has been little difference in the prevalence of obesity, including morbid obesity, between men and women in Scotland, since 2003.
8.3.3 Trends in mean adult BMI since 2003
Mean BMI has shown a general slight upward trend since 2003, and was highest since the start of the time series in both 2016 and 2017 (increasing from 27.1kg/m² in 2003 to 27.7kg/m² in 2016 and 2017). The trend in mean BMI for women was largely in line with that of all adults, for men mean BMI increased up to 2009 but has changed little since. Table 8.1
8.3.4 Adult BMI in 2017, by age and sex
In 2017, 33% of adults were in the healthy weight category. Women were significantly more likely than men to be in the healthy weight range (35% of women compared with 31% of men). This difference was largely due to the significant difference in the overweight category (BMI of 25 kg/m² to less than 30 kg/m²) of 7 percentage points between men 40%) and women (33%) whilst there was no significant difference between men and women in the obese category of BMI of 30 kg/m² or more (27% and 30% respectively).
In 2017, as in previous years, overweight and obesity prevalence and mean BMI varied significantly with age. Overweight including obesity prevalence (BMI of 25 kg/m² or over) increased with age (from 36% of those aged 16-24 to 78% of those aged 65-74) before dropping among those aged 75 and over (68%). A similar pattern was observed for prevalence of obesity including morbid obesity (BMI of 30 kg/m² or over) which increased from 14% among those aged 16-24 to 37% among those aged 65-74 before declining to 28% of those aged 75 and over.
The association between overweight including obesity (BMI of 25 kg/m² and over) and age followed a similar pattern to that of all adults for both men and women (Figures 8B and 8C).
However the patterns in obesity (BMI of 30 kg/m² or more) by age were significantly different for men and women, as shown in Figures 8B and 8C. Among men, prevalence of obesity markedly increased up to age 45-54 (from 11% to 36%), and then stabilised up to age 65-74 (ranging from 36% to 37%) before dropping to 34% among those aged 75 and over. Among women obesity prevalence increased more sharply at an earlier age, with the largest increase between age groups 25-34 and 35-44 (from 24% to 36%); prevalence then stabilised between ages 35-44 and 65-74 (ranging from 34% to 37%) before declining to 24% among those aged 75 and over.
There was a strong association between mean BMI and age for all adults. Mean BMI increased as age increased, before decreasing amongst people aged 75 or over. A similar pattern was found for men and women. Figures 8B and 8C, Table 8.2
8.4 Child Overweight and Obesity Prevalence
8.4.1 Trends in child healthy weight, overweight and obesity prevalence since 1998
In 2017, the proportion of children aged between 2 and 15 in the 'healthy weight' range was 72%, remaining at a similar level since 2015. The longer-term trend in the prevalence of children in the 'healthy weight' range has fluctuated since the beginning of the time series in 1998, with the lowest prevalence occurring in 2011 (65%) and the highest in 2015 and 2017 (both 72%).
The pattern over time was significantly different for boys and girls. There is some indication of a general trend of increasing prevalence of healthy weight in boys. In 2017 three quarters (75%) of boys were within the healthy weight range; this is the highest percentage since data collection began in 1998. Although this change over time for boys is statistically significant, there has been fluctuation over the time series so it will be important to monitor these figures next year to establish whether the indicated trend continues.
As shown in Figure 8D, there was no significant change in the prevalence of healthy weight for girls in 2017, with 69% of girls falling into within the healthy weight range. Following the trend for all children, healthy weight prevalence amongst girls has remained relatively steady since 1998.
Prevalence of children at risk of obesity in 2017 was the lowest recorded since time series began, at 13%. The percentage of children at risk of obesity has shown a steady decline since 2014 (with prevalence from 2003 to 2014 steady between 16-17%) to 15% in 2015, 14% in 2016 to 13% in 2017. The decline among all children in prevalence of risk of obesity has largely been driven by the decline in prevalence among boys from a peak of 20% in 2011 and 2012 to 12% in 2017. Figure 8D, Table 8.3
8.4.2 Child BMI categories in 2017, by age and sex
As in previous years, prevalence of healthy weight amongst children significantly decreased with age, with children aged 2-6 being the most likely to fall within the healthy weight range (78%, compared with 66% of children aged 12-15). The effect of age on prevalence of healthy weight was most profound amongst girls, with 76% of 2-6 year olds falling into the healthy weight range compared with 59% of 12-15 year olds; a difference of 17 percentage points (figures for boys were 79% and 70%, respectively, a difference of 9 percentage points). Table 8.4
8.5 Waist Circumference and Disease Risk (Based on BMI And Waist Circumference)
8.5.1 Trends in mean and raised waist circumference since 2003
Waist circumferences of adults aged 16 and over, on average, have increased since 2003 (men: 95.3cm in 2003 compared with 98.1cm in 2016/2017, women: 86.3cm in 2003, compared with 90.5cm in 2016/2017) using nurse equivalent measures. For both men and women, there was no significant increase in waist circumference between 2014/2015 and 2016/2017 using nurse equivalent measures.
As shown in Figure 8E, the proportion of men and women with a raised waist circumference continues to follow an upward trend. The proportion of men aged 16 and over with a raised waist circumference increased from 28% in 2003 to 38% in 2016/2017. The increase in raised waist circumference was more profound for women, increasing from 39% in 2003 to 54% in 2016/2017. For both men and women, the proportion of those aged 16 and over with a raised waist circumference in 2016/2017 was the highest since data was first collected for all adults in 2003. Figure 8E, Table 8.5
8.5.2 Body Mass Index (BMI) and waist circumference, 2016/2017 (combined)
Overall, 69% of women and 58% of men had at least an increased health risk based on their BMI and waist circumference in 2016/2017, with little change since 2014/2015[44]. Women were more likely than men to be categorised as 'high risk or above' (57% of women, compared with 42% of men).
As shown in Figures 8F and 8G, health risk increased with age for both men and women. Those aged 16-24 were least likely to have increased risk (24% of men and 41% of women), whilst those aged 65-74 were the most likely (78% of men and 83% of women).
Figures 8F and 8G, Table 8.6
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