Assessment of weight management interventions: the challenge of comparing apples and pears

Background
Obesity is an important public health problem. There is clear evidence that the rate of obesity has increased in recent years, and that obesity is associated with chronic health conditions, including diabetes. However, evidence is less clear for effective interventions to reduce bodyweight. It is crucial that we build up a strong knowledge base of effective interventions and that we encourage the discontinuation of ineffective interventions that waste public resources. As well as good quality academic intervention research, pragmatic assessments of ongoing weight management and obesity prevention programmes are urgently needed. However, this process is hampered by inconsistency in measurement. Research by public health practitioners in the UK suggests that although weight management interventions are being commissioned by various organisations, they are often poorly assessed, with inconsistent data being gathered for outputs, effects, and outcomes. The National Obesity Observatory set out to improve the assessment of weight management interventions through the development a standard evaluation framework that could be used to help assessors to obtain data that could be more easily compared with similar programmes.

Methods
The framework was developed in conjunction with leading academics and public health practitioners to ensure that the document was evidence-based and suitable for practical application by public health practitioners. Key criteria were developed and refined after consultation and testing with experts and the target audience.

Findings
We have published a standard evaluation framework for weight management interventions. This framework describes standards for a set of essential criteria for data to be obtained during assessment of weight management interventions, such as weight of participants before and after the intervention. Further desirable criteria are also listed that would improve the quality of any assessment, such as qualitative data for participants' perceptions of the intervention. A survey of key stakeholders registered with the National Obesity Observatory (n=175) showed that the framework had been used by three of four respondents. Discussions at training workshops, submitted case studies, and feedback from the Department of Health have shown the framework to be widely used and is mandatory for commissioning in some regions. We have now developed separate frameworks for physical activity and diet and nutrition interventions, which provide detailed guidance for measurement of key outcomes related to these determinants of obesity, with validated methods when possible.

Interpretation
Although the framework seems to have contributed to some systematic assessments of weight management interventions, some important challenges remain. Managers of obesity programmes in primary care trusts and local authorities continue to report that commissioners seem to be reluctant to allocate sufficient resources for assessment. A high demand for practical assessment support and training remains.