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An unpublished conference abstract presented at the European Congress on Obesity 2026 looked at rapid versus gradual weight loss and the risk of obesity-related complications.
Dr Adam Collins, Associate Professor of Nutrition, University of Surrey, said:
“This is an interesting clinical trial of weight-loss programmes, with substantial numbers (almost all of which were women) assigned to one of the two intervention groups (rapid or gradual weight loss). It is not clear whether energy intakes were adjusted as participants lost weight, but the energy deficits prescribed in both groups would still exceed reductions in obligatory energy expenditure or additional metabolic adaptation, meaning all participants were still in a calorie deficit at the end of the initial 14-week intervention and would have definitely lost weight. However, the rapid weight loss group (RWL), were prescribed a far greater overall energy (calorie) deficit than the gradual weight loss (GWL) group. As a result, you would obviously expect the RWL to have lost more weight. Yet the most interesting aspect of this study is not the immediate results of the weight loss intervention, but their weight after 1 year. Demonstrating that the RWL group maintained this greater weight loss 1 year later (an additional 4 percent of body weight on average), with a higher proportion achieving the target BMI of 27 at follow-up.
“Although the study does not include measures of body composition or energy expenditure, it directly relates to the common concern that large energy deficits drive disproportionate losses of fat-free mass and greater metabolic slowdown, thereby increasing the risk of regain. From our own observations of participants following very low energy diets (<1000kcal/day), loss of lean mass is not inherently greater with rapid weight loss, aside from early changes driven largely by glycogen and associated water loss. Moreover, overall reductions in lean mass and metabolic rate (including metabolic adaptation) appear to scale with the total weight lost, not with the speed at which it is lost.
“The conclusion from this study is that for individuals with substantial weight to lose, prescribing bigger energy deficits for more rapid weight loss is not only effective but can be durable, provided it is appropriately managed and supported.”
Dr Dimitrios Koutoukidis, Associate Professor in Diet, Obesity, and Behavioural Sciences; and dietitian, University of Oxford, said:
“This study is consistent with previous evidence showing that people who achieve greater weight loss early in a structured programme are often more likely to maintain a larger weight loss in the longer term. Rapid weight loss as part of a supervised and structured programme is the strongest predictor of maintaining the weight loss in the long term. However, not all weight loss programmes work for everyone. A helpful message for people trying to lose weight is that if one approach does not work for them, they should not feel let down but may benefit from keep trying different evidence-based approaches until they find one they can follow successfully. These findings should be interpreted with some caution. The press release is based on limited data from a randomised trial in mainly female participants, and it is hard to judge the quality of the study fully because it is currently available only as a conference abstract rather than as a peer-reviewed journal article.”
Dr Marie Spreckley, Research Programme Manager, University of Cambridge, said:
“This is an important study because it challenges the longstanding assumption that gradual weight loss is superior for long-term outcomes. In this trial, participants undertaking a structured and professionally supervised rapid weight loss programme achieved greater 1-year weight loss and were more likely to reach clinically meaningful BMI and waist-to-height ratio targets associated with lower obesity-related risk.
“A particular strength of the study is that both groups received substantial ongoing behavioural and weight regain prevention support throughout the full 52 weeks. This strengthens confidence that the improved outcomes observed in the rapid weight loss group were not simply explained by differences in follow-up care. The findings also reinforce the importance of continued clinical and behavioural support during obesity treatment, regardless of the rate of weight loss itself.
“However, the results should be interpreted within the context of an intensive and highly supervised intervention involving frequent in-person contact and ongoing professional input. Outcomes achieved under these conditions may not fully reflect what is achievable in routine clinical care, where access to long-term multidisciplinary support is often more variable.
“Overall, this study adds to growing evidence that rapid weight loss, when delivered safely and appropriately within a structured programme, can be an effective obesity treatment strategy and should not automatically be considered less sustainable than gradual weight loss.”
‘Rapid versus Gradual Weight Loss for Reducing Risk of Obesity-Related Complications: A Treat-to-Target Analysis of an RCT’ by Line Kristin Johnson et al. was presented at ECO 2026 and the embargo lifted at 23:01 UK Time on Thursday the 14th of May 2026.
Declared interests
Dr Adam Collins: “No declarations of interest”
Dr Dimitrios Koutoukidis: I have been an investigator in independently funded trials where the weight loss programmes have been provided for free by commercial weight loss companies.
Dr Marie Spreckley: “No conflicts of interest to declare in relation to this study.”