Losing weight is relatively simple; keeping it off long term is the challenge. The maintenance of lost weight has become one of the most arduous and enduring problems in the area of weight control, and is one with which researchers and practitioners continue to grapple. Behavioural treatment, whatever the dietary make-up, consistently elicits modest short term weight loss; however, weight is more often than not regained over time. This body of work explores this conundrum, in the workplace and in the dietitian clinic settings. Gaps highlighted in the literature gave rise to a series of studies with several novel elements that become the starting point for New Zealand-based evidence, and that contribute important findings to the limited international research in this field.

The first of two studies in the workplace was formative and explored the weight loss and maintenance experiences of New Zealand employees, as well as their ideas for an ideal workplace-based programme. These findings assisted with determining the design and contents of a novel ‘small-changes’ weight loss and maintenance intervention. The small-changes approach focuses on promoting small alterations in lifestyle behaviour, which when compared with severe, restrictive regimes, is proposed to result in better adherence to newly formed habits, giving rise to sustained behaviour change. While initially intended as a prevention strategy for population weight gain, the approach has been used in this study as the underpinning treatment strategy for sustained weight loss, which is as yet uninvestigated in the workplace setting. The workplace is an ideal setting for such interventions; if improvements in health–and in particular productivity–outcomes are shown, employers are likely to commit funds for on-going work. The workplace, which has a strong social support element, can then become a sustainable business setting for the delivery of health promotion, independent of public health funding. Using a quasi-experimental design, the second study investigated the efficacy of a 12-week small-changes weight loss intervention, with and without a 9-month maintenance component, on weight, health and productivity outcomes in two workplaces (n=102). Relative to a prior usual-care brief intervention evaluated after 12 months, the small-changes programme showed beneficial weight loss. For small-changes interventions, weight was reduced at 12 weeks and kept off at 12 months, regardless of maintenance. Mean 12-month weight losses were modest (-3.5% ± SD range 5.6-5.8%), with approximately one-third of participants losing and maintaining a clinically meaningful amount of weight (i.e., ≥5%). Some improvements in health outcomes were shown, and at an individual level weight change was associated with at most only small improvements or small reductions in productivity. Further research on productivity outcomes in relation to weight change is warranted; however, the need for a universal measure of productivity is critical if these complex relationships are to be investigated in future trials.

The research direction of this body of work subsequently shifted from the workplace to the dietitian clinic setting. The shift came about after comparison of workplace findings with those from other settings, which revealed a lack of international evidence on the treatment efficacy for the dietetic profession, one which is well known for its association with weight loss treatment. This important literature gap prompted a two-part investigation into the consultancy practices and client weight loss and maintenance outcomes of private practice dietitians. The first component of the study was novel for the New Zealand setting. Findings showed that dietitians (n=37) favoured a flexible, small-changes consultancy approach over structured calorie / portion-prescription for weight loss treatment with their clients, who were predominantly female, middle-aged and of New Zealand / European ethnicity. The subsequent component of the study was novel on an international level and revealed that private practice dietitians in New Zealand were successful in achieving and sustaining clinically meaningful weight loss in approximately one-third of their clients. There was little effect of consultation approach on weight loss; however, dietitians that offered a fixed-term course of treatment were able to achieve 38% greater client retention than those offering their services by flexible treatment. Females were more successful in losing weight and maintaining lost weight than males, highlighting that alternative treatment strategies may be needed for males. Due to the lack of client follow-up beyond the time spent in the clinic, longer term weight loss outcomes are unknown. These findings make an important contribution to the overall body of knowledge of individual treatment efficacy for weight loss and maintenance as well as for the dietetic profession itself.

Finally, weight loss outcomes from the workplace and dietitian clinic settings described were compared with those from other weight loss treatments using cost-effectiveness, treatment efficacy and benefit vs harm as comparison metrics. Using a common unit of dollars per kilogram of weight loss, the cost of losing weight in New Zealand was able to be appraised. Findings showed that 12 months of behavioural weight loss treatment was more cost-effective (i.e., $145-241/kg) with less risk of harm than other treatments, such as the similarly effective, but more costly pharmaceutical option ($514-786/kg). Bariatric surgery was less cost-effective ($771-2667/kg); however, for the refractory case of severe obesity with associated co-morbidities, the benefits of this type of treatment may outweigh the high financial one-off treatment cost and associated risk of harm.

In light of the diverse application of data analysis methods (i.e., completers or intention-to-treat) to weight loss outcomes in the studies reviewed, and the associated quandary regarding preferred usage, the data throughout this body of work were expressed using several alternative approaches. In addition to mean weight loss outcomes, findings have been presented as proportions of individuals achieving clinically meaningful weight loss, and interpreted using the evidence-based medical tools, numbers needed to treat (NNT) and numbers needed to harm (NNH). The inclusion of these approaches may allow for a greater depth of meaning about treatment at an individual level.

Taken together, behavioural weight loss treatment by workplace programme or dietitian clinic care are relatively cost-effective compared with other treatments, and are subject to minimal harm (i.e., a one-in-four to one-in-eight chance of gaining weight). The benefit is one in every three individuals undergoing such treatment experience clinically meaningful short to medium term weight loss.