New research presented at the European Congress on Obesity (ECO 2026) in Istanbul, Turkey, shows that rapid weight loss (RWL) is much more effective than gradual weight loss (GWL) in both achieving higher weight loss and also sustained weight loss at one year.
The study was led by Dr. Line Kristin Johnson, Department of Endocrinology, Obesity and Nutrition, Vestfold Hospital Trust, Tønsberg, Norway, and colleagues. The Center is a collaborating center with the European Association for the Study of Obesity (EASO) (EASO-COM-Center), which leads obesity advocacy and education efforts in Europe and organizes ECO.
There exist long?standing beliefs suggesting that rapid weight loss (RWL) is unhealthy and that losing weight very quickly increases the likelihood of weight regain. However, these concerns are largely based on observational data, historical assumptions, or small, methodologically limited studies.
Overall, the scientific evidence directly supporting these claims is limited and inconsistent, and high?quality randomized controlled trial evidence is relatively sparse.
A recent large population-based cohort study, concluded that a body-mass index (BMI) of ?27 kg/m² and a waist-to-height ratio (WHtR) of ?0.53 after weight loss may represent clinically meaningful treatment targets for reducing the 10-year risk of obesity-related complications (type 2 diabetes, hypertension, atherosclerotic cardiovascular disease, and hip/knee osteoarthritis).
In this new study, the authors aimed to assess the comparative effectiveness of a RWL program versus a GWL program in achieving these treatment targets.
This 52-week investigator-initiated, randomized clinical trial was conducted as a collaboration between the Department of Endocrinology, Obesity and Nutrition, Vestfold Hospital Trust and Roede AS, one of Norway’s leading and most established providers of commercial weight- loss programs.
A total of 284 adults with obesity (BMI ?30) (257, 90% women) were randomized (1:1) to either a 16-week food-based RWL-program (weeks 1–8:
Estimated energy expenditure was calculated by estimating the participants’ resting energy expenditure and adjusted based on whether they had low, medium or high physical activity.
Following the initial weight loss phase, participants in both groups entered an identical 36-week weight-regain prevention program.
The interventions included weekly in-person weight-loss group sessions from week 1 to week 16, and thereafter, in-person group meetings every 14 days for the first three months, followed by monthly meetings or individual contacts via webinars, video or telephone for the remaining five months of the study.
In these sessions, participants were advised to increase their daily energy intake by 100–300 kcal during the first month, until weight stability was achieved.
Thereafter, daily energy intake was adjusted as needed in response to any concomitant weight changes throughout the eight?month weight?maintenance phase. Participants were free to decide whether they wished to maintain their weight or pursue further weight loss. The majority opted for additional weight reduction following the initial 16?week period.
The food composition in both programs was based on current Norwegian dietary recommendations issued by the Norwegian Directorate of Health. Core recommendations included consumption of healthy foods such as vegetables, fruits, whole grains, low?fat dairy products, fish, eggs, lean meat, and other protein?rich foods, while limiting the intake of saturated fats and added sugars.
The primary outcome was one-year percent total body weight loss (%TBWL), and the proportion of participants achieving a BMI of ?27 kg/m² or a WHtR ?0.53 after one year, were exploratory outcomes.
Of the 284 participants, 142 were randomized to the RWL and 142 to the GWL program. At baseline, in the RWL group, the mean age was 48.5 years, body weight 102.4 kg, height 169 cm, BMI 35.8 kg/m², waist circumference 112.5 cm, and WHtR 0.67. Corresponding values in the GWL group were 47.7 years, 103.0 kg, 168 cm, 36.5 kg/m², 112.8 cm, and 0.67.
During the initial 16 weeks, participants in the RWL group lost significantly more body weight than those in the GWL group, with mean %TBWL of -12.9% and -8.1%, respectively, corresponding to a between-group difference of -4.8%.
At one year, the significant difference was maintained, with mean %TBWL of -14.4% in the RWL group and -10.5 in the GWL group, corresponding to a between-group difference of -3.9 percentage points.
The proportion of participants achieving a BMI ?27 kg/m² was significantly higher in the RWL group than in the GWL group at both 16 weeks (13.8% vs. 0.8%) and one year (28.3% vs. 9.7%). Similarly, a higher proportion achieved WHtR ?0.53 in the RWL group at 16 weeks (24.2% vs. 8.9%) and at one year (33.0% vs. 18.4%).
The authors conclude, “Among adults with obesity, participation in a structured rapid weight loss program resulted in significantly greater weight loss at one year, and higher rates of achieving clinically meaningful BMI and WHtR targets compared with a gradual weight loss approach.
“These findings indicate that, when provided within a controlled and professionally supervised setting, rapid weight loss may represent a more effective method than gradual weight loss for reaching key body weight targets associated with reduced obesity-related health risks.”
Dr. Johnson adds, “Our results clearly challenge the prevailing belief that slow and steady gradual weight loss is necessary to prevent weight regain and reduce obesity-related complications.
“By contrast, we show that rapid weight loss is not associated with weight regain, and, more importantly, that a larger proportion of participants undergoing rapid weight loss—compared with gradual weight loss—achieved clinically meaningful treatment targets for reducing the 10-year risk of type 2 diabetes, hypertension, atherosclerotic cardiovascular disease, and hip/knee osteoarthritis.
“These findings are particularly relevant given the urgent need for effective weight-loss and weight?maintenance strategies. As many individuals with obesity cannot access or afford medical or surgical treatments, our results support the potential of effective, commercially available weight?reduction programs to help reduce the growing burden on public health care systems.”
Key medical concepts
Provided by
European Association for the Study of Obesity
The content is provided for information purposes only.