Body size

A healthy body size is recognised as important for good health and wellbeing. Evidence shows that obese children and adults are at greater risk of short- and long-term health consequences (see Annual Update of Key Results 2013/14: New Zealand Health Survey).

Body mass index (BMI) provides a useful population-level indicator of excess body weight. It is a measure of weight adjusted for height, and is calculated by dividing weight in kilograms by the square of height in metres (kg/m2). This measure is used internationally to classify underweight, overweight and obesity. It should be noted that BMI is a crude measure, and does not distinguish between weight associated with muscle and weight associated with fat. However, it is considered to be a good estimate of increased risk of health conditions associated with obesity (see Global Database on Body Mass Index, World Health Organization).

From July 2012, the New Zealand Health Survey measured height using a laser meter, replacing the stadiometers used in the 2006/07 and 2011/12 surveys. Refer to the Indicator Interpretation Guide 2013/14: New Zealand Health Survey for more details.

Table 13: International BMI cut-off points for adults aged 18 years and over [1]
Classification BMI score (kg/m2) Risk of health conditions
Underweight <18.50 Low risk
Normal range 18.50–24.99 Average risk
Overweight 25.00–29.99 Increased risk
Obese ≥ 30.00 Substantially increased risk

Details on the classification of overweight and obesity in children under 18 years can be found in Cole et al’s Establishing a standard definition for child overweight and obesity worldwide: international survey and Body mass index cut offs to define thinness in children and adolescents: international survey.

There is an association between BMI and health risk (see Body mass index and cardiovascular disease in the Asia-Pacific Region: an overview of 33 cohorts involving 310 000 participants, Asia Pacific Cohort Studies Collaboration), and therefore data on BMI distribution, as well as BMI cut-offs, is useful. For this reason, this chart book presents data on mean BMI and mean waist measurement (cm) as well as the prevalence of overweight and obesity.

Indicator Māori Non-Māori
Males Females Total Males Females Total
Table 14: Body size indicators, children aged 5–14 years, by gender, Māori and non-Māori, 2013/14 [2]
Overweight, 5–14 years, percent, 2013/14 28.8
(24.0–34.1)
29.2
(24.6–34.3)
29.0
(25.3–33.0)
18.9
(16.1–22.1)
23.4
(19.7–27.5)
21.1
(18.7–23.7)
Obese, 5–14 years, percent, 2013/14 18.1
(14.0–23.1)
17.7
(13.1–23.4)
17.9
(14.5–21.9)
7.8
(5.8–10.4)
9.1
(7.0–11.7)
8.4
(6.8–10.4)
Mean BMI score, 5–14 years, 2013/14 19.5
(19.1–20.0)
19.3
(18.9–19.7)
19.4
(19.1–19.7)
18.3
(18.0–18.5)
18.4
(18.1–18.6)
18.3
(18.1–18.5)

Māori children were more likely to be overweight than non-Māori children (RR 1.38, CI 1.15–1.65). Māori children were more than twice as likely to be obese as non-Māori children (RR 2.13, CI 1.58–2.87). Māori children had a slightly higher mean BMI score than non-Māori children (RR 1.06, CI 1.04–1.09).

Indicator Māori Non-Māori
Males Females Total Males Females Total
Table 15: Body size indicators, adults aged 15 and over, by gender, Māori and non-Māori, 2013/14 [2]
Overweight, 15+ years, percent, 2013/14 33.4
(30.0–37.0)
27.6
(24.0–31.4)
30.4
(27.8–33.0)
39.2
(37.3–41.3)
28.2
(26.6–29.9)
33.6
(32.3–34.9)
Obese, 15+ years, percent, 2013/14 42.0
(38.2–45.8)
47.2
(43.8–50.6)
44.7
(42.1–47.3)
24.7
(22.8–26.6)
24.7
(23.0–26.6)
24.7
(23.6–25.9)
Mean BMI score, 15+ years, 2013/14 29.8
(29.2–30.3)
30.6
(30.1–31.1)
30.2
(29.8–30.6)
27.2
(27.0–27.5)
26.9
(26.6–27.2)
27.1
(26.9–27.2)
Mean waist measurement (cm), 15+ years, 2013/14 99.1
(97.7–100.5)
94.0
(92.7–95.4)
96.4
(95.4–97.4)
93.7
(93.0–94.4)
84.4
(83.7–85.0)
88.9
(88.5–89.4)

Māori adults were less likely than non-Māori adults to be overweight (RR 0.89, CI 0.82–0.96). However, Māori adults were more than 1.5 times as likely to be obese as non-Māori adults (RR 1.76, CI 1.65–1.87). Māori adults had higher mean BMI scores (RR 1.11, CI 1.10–1.13) and mean waist measurements (RR 1.08, CI 1.07–1.09) than non-Māori adults.


1. Note: Risk only includes health conditions associated with increasing BMI.

Source: WHO 2007


2. Notes:

Source: 2013/14 New Zealand Health Survey, Ministry of Health

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