Table 8.

Core and optional outcome and definition/instrument sets

Core Outcome Set
Process Outcomes
Item	Definition	Instrument/Measurement/Presentation to be Used/Reported (Baseline)	Instrument/Measurement/ Presentation to be Used/Reported (Follow‐up)
Age	How old participants are/the age (in years) of participants	Mean age of participants in years % of participants in age bands (16‐24, 25‐34 , 35‐44, 45‐54, 55‐64, 65‐74, 75+ y)
Gendera	How participants identify themselves with regard to being male, female, or nonbinary/third gender	% of male, female, or other participants
Ethnicitya	The social group with common national and cultural tradition that participants identify as belonging to, eg, white/white British, Asian/Asian British, black/African/Caribbean/black British	% of participants identifying as being white, black, Asian, or Minority Ethnicities
Deprivation categorya	A measure of the level of poverty in the area in which the participant lives	Scotland—% of participants in each Scottish Index of Mass Deprivation (SIMD) quintile England—% of participants in each English Index of Mass Deprivation (EIMD) quintile Wales—% of participants in each Welsh Index of Mass Deprivation (WIMD) quintile Northern Ireland—% of participants in each Northern Ireland Multiple Deprivation Measure (NIMDM) decile
Physical disabilitya	Whether participants have a recognised physical disadvantage or disability
Learning disabilitya	Whether participants have a recognised mental/cognitive disadvantage or disability
Formally diagnosed with a mental health conditiona	Whether participants have a current mental health condition as diagnosed by a GP or health professional	% of participants answering yes
Referral to specialist services (real world services only)	Whether a participant has been referred to a specialist management service (tier 3 or 4) by a GP or tier 2 weight management service after failing to lose the required amount of weight via a lifestyle weight management programme or due to a condition needing specialist input.		% of participants
Repeat referrals (real world evaluations only)	Whether a participant has been referred to the weight management service on more than one occasion.		% of participants previously referred to the service, not necessarily having attended any sessions) % of participants answering yes, having previously attended at least 1 weight management session
Attendance	How many people attended the weight management service		Mean % of core/mandatory sessions attended by participants
Completion	How many people finished the weight management programme		% of participants who attended 80% of possible/core/mandatory sessions
Reason for dropout	Why those participants who did not complete the programme failed to do so.		% of participants who dropped out due to: Dissatisfaction with the intervention (unrelated to weight loss) Poor weight loss Illness/ hospitalisation Pregnancy Change in personal circumstances/social reason Moving from the geographical area Any other reason Unknown reason
Core Outcome Set
Outcomes
Item	Definition	Instrument/Measurement/Presentation to be Used/Reported (Baseline)	Instrument/Measurement/ Presentation to be Used/Reported (Follow‐up)
Weight	The measurement of how heavy a participant is in kilograms (kg) or stones and pounds	Mean weight of participants in kg	Mean change in participants' weight in kg Mean % weight change of participants % of participants achieving ≥5% weight loss % of participants achieving ≥10% weight loss
Body mass index (BMI)	An approximate measure of whether a participant is overweight or underweight, calculated by dividing their weight in kilograms by the square of their height in metres	Mean BMI of participants % of participants in BMI categories <25, 25‐29.9, 30‐34.9, 35‐39.9, 40‐49.9, 50‐59.9, ≥60	mean change in participants' BMI
Diabetes status	Whether a participant has diabetes, a condition, which occurs when the body does not produce enough insulin to function properly, or the body's cells do not react to insulin. This means glucose stays in the blood and isn't used as fuel for energy. Type 2 diabetes is often associated with obesity and an increased risk of developing cardiovascular disease.	% of participants with type 2 diabetes mellitus (based on self‐report, case record, or blood test)	Mean change in HbA1c levels of those participants with T2DM
Quality of life (QoL) score	A measure of the general well‐being of participants.	Mean EQ‐5D‐5L scores of participants	Mean change in EQ‐5D‐5L scores of participants
Learning disability QoL score	A measure of the general well‐being of participants with a learning disability.	Mean Personal Wellbeing Index‐Intellectual Disability (PWI‐ID) score(s) of participants	Mean change in PWI‐ID score(s) of participants
Adverse events/unintended consequences	Whether participants suffered any unfortunate side effects as a result of attending the weight loss service.		Number of participants experiencing a worsening of a pre‐existing medical condition, such as An undiagnosed eating disorder Other pre‐existing medical conditions Number of participants sustaining an injury during a physical activity session run by the weight management service
Participant satisfaction	How happy/satisfied participants were with the weight loss service.   **In this instance, the weight management service should select the questionnaire/method they feel is most appropriate for their use.**		Comments and scores indicate that neither of the suggested instruments for measuring patient satisfaction is ideal. Therefore, it is proposed that no instrument is selected. The two options below will be given as suggestions but other methods could be used. Mean Outcomes and Experiences Questionnaire (OEQ) score adapted to suit weight management services Mean NHS Friends and Family Test (FFT) score
Cost effectiveness	The value for money of the weight management service in terms of long term economic benefits to the NHS.		The Public Health England Weight Management Economic Assessment Tool: http://webarchive.nationalarchives.gov.uk/20170110165804/http://www.noo.org.uk/visualisation/economic_asessment_tool
Guidance for Presentation of Results (Core Outcome Set)
Item	Definition	Presentation to be Used
Presentation of results	Which participants' outcomes to include in reporting	Report outcomes for all participants attending >1 active weight loss session(s) and therefore having weight change data (does not include introductory sessions/information sessions about the service) Report outcomes for all participants completing the programme
12‐mo follow‐up	Reporting outcomes 12 mo after starting the weight loss programme
24‐mo follow‐up	Reporting outcomes 24 mo after starting the weight loss programme
Missing data	How to deal with participants with missing weight data (usually because they have dropped out of the programme)	baseline observation carried forward (BOCF) and last observation carried forward (LOCF) for data at <12 months   BOCF for data at ≥12 months
Optional Outcome Set
Process Outcomes
Item	Definition	Instrument/Measurement/Presentation to be Used/Reported (Baseline)	Instrument/Measurement/Presentation to be Used/Reported (Follow‐up)
Reach (% eligible population who are referred to/take up weight management service)	The percentage of the eligible population (people who are overweight or obese within that particular geographical area) referred to the weight management service.		For a specific population subgroup of concern, what % of that population has been referred to/ attended the weight management service. Local data (eg, Quality and Outcomes Framework) can be used to obtain prevalence rates. Population subgroups of interest: Age <30 Male People with T2DM Other subgroups
Representativeness (how similar the people attending the service are to the local eligible population)	How representative of the entire eligible population (people with body mass in the overweight or obese range within that particular geographical area) the people attending the weight management service are.		Based on age of participants Based on sex of participants Based on BMI of participants Based on deprivation category of participants Based on ethnicity of participants Based on diabetes status of participants Based on the geographical spread of the home addresses of participants
Referral to linked services	The number of participants referred to services linked to weight management services		% of participants referred to smoking cessation services, mental health services, alcohol services etc
Sources of referral	Where participants received their referral to the weight management service	% of participants receiving their referral from each possible source dependent on service, eg, from primary care, from secondary care, self‐referral, from allied health professionals, from pharmacy, from tier 3 weight management services, from tier 4 weight management services
Mobility issues	Whether participants are unable to move with ease and without restriction. Being overweight has been associated with restricted mobility.	% of participants who have difficulty accessing certain weight loss service venues and have impaired ability to exercise
Optional Outcome Set
Outcomes
High blood pressure	Whether a participant has high blood pressure. High blood pressure increases the risk of developing cardiovascular disease.	% of participants with high blood pressure based on patient report/medication/case notes % of participants with high blood pressure based on blood pressure readings	Change in % of individuals with blood pressure above current recommended treatment thresholds (ie, normotensive or adequately treated)
Blood pressure	The pressure of blood in the arteries, the vessels that carry blood from the heart to the rest of the body. A certain amount of pressure is required to get the blood around the body but consistently high blood pressure increases the risk of cardiovascular disease.	Mean systolic and diastolic blood pressure of participants	Change in mean systolic and diastolic blood pressure of participants
Cardiovascular risk	A measure of how likely participants are to develop cardiovascular disease, including heart disease and stroke	% of participants with previous cardiovascular disease (CVD), including myocardial infarction, stroke, transient ischaemic attack (TIA), angina, and peripheral vascular disease % of participants with high CVD risk (previous CVD or a high cardiovascular risk score—N.B. information on blood pressure and lipids would be required to calculate the risk score) % of participants with a high cardiovascular risk score (primary prevention/not those with previous cardiovascular disease) mean CVD risk score of participants (primary prevention/not those with previous cardiovascular disease)	% of participants with a high cardiovascular risk score (primary prevention/not those with previous cardiovascular disease) change in mean cardiovascular risk score of participants (primary prevention/not those with previous cardiovascular disease)
High cholesterol/ lipids	A measure of whether a participant has an abnormal amount of fat and/or cholesterol, known as lipids, in their blood (also called dyslipidaemia). Being overweight can increase the likelihood of developing dyslipidaemia. Dyslipidaemia is associated with increased risk of developing cardiovascular disease.	% of participants with high cholesterol/lipids based on self‐report /case records Mean total cholesterol/ high density lipoprotein/ triglycerides of participants as obtained via blood test	Mean change in total cholesterol/ high density lipoprotein/ triglycerides of participants as obtained via blood test
High future risk of diabetes (impaired fasting glucose, impaired glucose tolerance, raised HbA1c levels, previous gestational diabetes)	Whether measures of the amount of glucose in a participant's blood suggests he/she is likely to develop type 2 diabetes in the future.	% of participants with a medical record of high diabetes risk (HDR) as determined by measuring HbA1c/fasting glucose/Oral Glucose Tolerance Test (OGTT) (either measured during intervention or in medical records)	% of all participants with HDR as determined by measuring HbA1c/fasting glucose/OGTT (either measured during intervention or in medical records) % of those participants identified as having HDR at baseline who still have HDR (as determined by measuring HbA1c/fasting glucose/OGTT) , normoglycemia or type 2 diabetes
Overall measure of comorbidity	Measure of the presence of additional diseases or disorders co‐occurring with obesity/being overweight	Mean Edmonton Obesity Staging System (EOSS) score	Mean change in EOSS score
Depression	Whether a participant suffers from a mental illness characterised by a profound and persistent feeling of sadness or despair and/or a loss of interest in things that once were pleasurable.	% of participants with depression based on patient report/medication/case notes % of participants on medication for depression Mean Patient Health Questionnaire‐9 (PHQ‐9) score of participants	Change in % of all participants on medication for depression Change in % of those patients identified as having depression at baseline on medication for depression Mean change in PHQ‐9 questionnaire score of participants
Self‐confidence and self‐esteem	How participants feel about their own abilities and worth	Mean Warwick‐Edinburgh Mental Well‐being Scale (WEMWBS) score	Mean change in WEMWBS score
Importance of weight loss	How important participants feel it is for them to lose weight	Mean Dieting Readiness Scale score(s)
Disordered eating	Whether participants have disturbed and unhealthy eating patterns that can include restrictive dieting, compulsive eating or skipping meals. Disordered eating can include behaviours, which reflect many but not all of the symptoms of feeding and eating disorders such as anorexia nervosa, bulimia nervosa, and binge eating disorder.	% of participants with disordered eating (defined as per service)	Change in % of participants with disordered eating (defined as per service)
Prescription of anti‐obesity medication	The number of participants taking drugs to help reduce or control their weight	% of participants on any anti‐obesity medication (total and by class/medication)	Change in % of participants on anti‐obesity medication (total and by class/medication)
Guidance For Presentation of Results (Optional Outcome Set)
3‐mo follow‐up	Reporting outcomes 3 mo after starting the weight loss programme
6‐mo follow‐up	Reporting outcomes 6 mo after starting of the weight loss programme
18‐mo follow‐up	Reporting outcomes 18 mo after starting the weight loss programme

Note. The expert group agreed on a final core outcome and corresponding definition/instrument set consisting of 24 items. Twelve of these items were designated as processes, eight were designated as outcomes, and four were designated as guidance for presentation of results. Experts agreed on an optional outcome set consisting of 19 items; five processes, 11 outcomes, and three items relating to presentation of results.

^aThese items are considered “protected characteristics” and therefore, in keeping with government guidelines, have been included in our core outcome set. These items are more relevant for real world services which are required to report such items to higher authorities. As such, these items are only core or mandatory for reporting when required in real life.