Behaviour-change techniques

Behaviour-change techniques are techniques aimed at changing the way someone acts (and so, logically, their thinking patterns). In this case, the changes relate to dietary intake and eating behaviour, physical activity and sedentary behaviour.

Body mass index (BMI) z score

BMI z score is a measure of how many standard deviations a child or young person's BMI is above or below the average BMI for their age and gender. (This is based on a reference population known as a child growth reference.) For instance, a z score of 1.5 indicates that a child is 1.5 standard deviations above the average value, and a z score of -1.5 indicates a child is 1.5 standard deviations below the average value.

The advantage of using BMI z scores, instead of BMI, is that it allows direct comparison of BMI (and any changes in BMI) across different ages and by gender. This term is sometimes used interchangeably with 'BMI standard deviation score' (BMI SDS). See the National Obesity Observatory's simple guide to classifying body mass index in children.

Care is needed when interpreting BMI z scores using the UK 1990 centile charts for black, Asian and other minority ethnic groups. There is evidence to suggest that adults from these groups are at risk of obesity-associated conditions and diseases at a lower BMI than the white population. See NICE's guideline on obesity: identification, assessment and management. However, there are no growth reference charts for children from minority ethnic groups. (For more details on the differences in BMI thresholds as a trigger for disease among children in these groups, see the National Obesity Observatory's report on obesity and ethnicity.)

Body mass index (BMI)

Body mass index is defined as a person's weight in kilograms divided by the square of their height in metres and is reported in units of kg/m2. Specific cut-off points are used to assess whether a person is a healthy weight, underweight, overweight or obese. For children and young people these are related to age and gender.

Child and adolescent mental health services (CAMHS)

Child and adolescent mental health services are specialist mental health services for children and young people.

Clinical commissioning groups

Clinical commissioning groups (CCGs) are responsible for commissioning a range of healthcare services for children and adults. This includes specialist obesity services (sometimes called tier 3 services). The groups do not directly commission lifestyle weight management services (sometimes called tier 2 services). Rather, they work with local authorities to coordinate and integrate planning and commissioning through the health and wellbeing board.


Comorbidities are diseases or conditions that someone has in addition to the health problem being studied or treated. Some comorbidities, such as type 2 diabetes, are associated with being overweight or obese, because the risk of developing them increases with an increasing BMI.

Complex obesity

Complex obesity occurs when someone who is obese has additional and related diseases or conditions, for example, type 2 diabetes. It can also occur when obesity results from an underlying condition, for example, an endocrine disease or condition, or when it is associated with various syndromes (such as Prader-Willi syndrome). Complex obesity can occur regardless how obese the person is, although it is more likely as BMI increases.


Evaluation involves assessing whether an intervention is meeting its objectives. This might include outcomes (for example, effectiveness in terms of BMI z score reduction or value for money). It might also include evaluation of processes (for example, how successful recruitment is or how acceptable the intervention is to participants).

Health and wellbeing boards

Health and wellbeing boards are based in upper tier and unitary local authorities. They aim to improve health and care services and the health and wellbeing of local people. They bring together key commissioners in the locality, including representatives of clinical commissioning groups, public health, children's services and adult social services. They include at least 1 elected councillor and a representative of HealthWatch. The board develops a health and wellbeing strategy for the local area. This is based on an assessment of local needs, including a joint strategic needs assessment.

Joint strategic needs assessments (JSNAs)

Joint strategic needs assessments (JSNAs) identify the current and future health needs of a local population. They are used as the basis for the priorities and targets set.

Lifestyle weight management programmes

In this guidance, lifestyle weight management programmes refer to programmes that focus on diet, physical activity, behaviour change or any combination of these elements.

Lifestyle weight management services

In this guidance, lifestyle weight management services (sometimes called tier 2 services) refer to services that help people in a particular geographical location who are overweight or obese. The service can be made up of 1 or more lifestyle weight management programmes. The programmes are usually based in the community and may be run by the public, private or voluntary sector.

Local authority commissioners

Local authorities commission some public health services for children and young people aged 5 to 19 years. They have a mandatory responsibility to deliver the National Child Measurement Programme. They also commission non-mandatory services such as school nursing and community-based weight management services.


Monitoring involves routine collection, analysis and reporting of a set of data to assess the performance of a weight management programme according to the service specification and intended health outcomes.

National Child Measurement Programme

The National Child Measurement Programme (NCMP) measures the weight and height of children in reception class (aged 4 to 5) and Year 6 (aged 10 to 11). The aim is to assess the prevalence of obesity and overweight among children of primary school age, by local authority area. These data can be used at a national level to support local public health initiatives and inform local services for children.

NHS England

NHS England commissions primary care, clinical and specialised services. It also commissions public health services for children aged 0 to 5 years (including health visiting and much of the Healthy Child Programme). In 2015, the organisation's public health services transfer to local authorities.

Obesity care or weight management pathway

An obesity care or weight management pathway represents the various routes through local services that an individual child or young person might follow to help them manage their weight. A comprehensive obesity care or weight management pathway spans both prevention and treatment, offering services at different levels or 'tiers'. Children and young people may move between these services. In adult obesity care pathways, there may also be a further tier focusing on surgical treatment (sometimes called tier 4 services). Surgery is recommended for children and young people only in exceptional circumstances, see NICE's guideline on obesity prevention.

Physical activity

Physical activity includes the full range of human movement. It includes everyday activities such as walking or cycling for everyday journeys, active play, work-related activity, active recreation (such as working out in a gym), dancing, gardening or playing active games, as well as organised and competitive sport.

Positive parenting skills training

Positive parenting skills training is training for parents and carers that aims to improve children and young peoples' behaviour. It fosters effective boundary setting and the need to reward and praise children in a way that promotes positive relationships and self-esteem.

Providers of lifestyle weight management programmes

Providers of lifestyle weight management programmes are private, public or voluntary sector organisations offering lifestyle weight management services in the community or in (or via) primary care settings.

Public Health England

Public Health England is an executive agency of the Department of Health. It provides advice and expertise to local authorities, NHS England and clinical commissioning groups on the commissioning of public health services.

Rolling programmes

Rolling programmes are lifestyle weight management programmes that run on a continuous basis. Participants can start and end the programme at different points, covering the same material over the same number of weeks or months, but not necessarily in the same order. An advantage is that participants referred part way through a programme cycle do not have to wait for it to be completed and a new one to start before they join.

Sedentary behaviour

Sedentary behaviour describes activities that do not increase energy expenditure much above resting levels. Sedentary activities include sitting, lying down and sleeping. Associated activities, such as watching television, are also sedentary.

Specialist obesity services

In this guidance, specialist obesity services (sometimes called tier 3 services) usually refer to clinical treatments provided by specialist services. This may include the use of drugs. These services could be for children or young people with severe or complex obesity, or with other special needs.

Stimulus control

Stimulus control relates to the way someone's behaviour changes as a result of a particular trigger. For example, having the television on can encourage someone to sit and watch it (that is, adopt sedentary behaviour); turning it off could encourage them to do something that is more physically active. Or if a person trying to manage their weight finds it hard to resist high fat or sugary snacks, family members could be asked not to eat those snacks around that person.

Universal obesity prevention services

In this guidance, universal obesity prevention services (sometimes called tier 1 services) refer to activities to help prevent everyone, regardless of their weight, from becoming overweight or obese. These universal services help raise awareness of the importance of maintaining a healthy weight. They also develop and promote services, facilities and policies that enable children, young people and their families to eat more healthily and be more physically active. For example, by providing walking and cycling routes and safe areas for active play, or by working with caterers in schools, colleges and early years organisations to improve the food choices on offer.

UK 1990 centile charts

UK 1990 centile charts, also referred to as the British 1990 growth reference (UK90), are charts used for children aged 4 years and older to determine whether their BMI is appropriate for their age and gender. See the National Obesity Observatory's simple guide to classifying body mass index in children.