05/26/2026
Losing weight rapidly yielded greater and more sustainable weight loss than gradual loss in a real-world, randomized controlled trial.
Previous studies conducted in academic centers, involving highly selected participants and using severe caloric restriction through meal replacements products, demonstrated that rapid weight loss (RWL) is superior to gradual approaches, Line Kristin Johnson, PhD, Vestfold Hospital Trust, Tønsberg, Norway, told Medscape Medical News.
“Our study was designed to evaluate whether [RWL] can be a safe and effective strategy for achieving weight reduction and preventing weight regain in a pragmatic, real-life setting” using conventional foods, she said.
Johnson presented the findings at the 33rd European Congress on Obesity (ECO) 2026.
Rapid weight loss proved more effective and sustainable than gradual loss in a real-world trial, achieving significant weight reduction and meeting clinical targets for reducing obesity-related health risks, challenging the belief that slow weight loss is superior.
A recent large population-based cohort study concluded that a BMI ≤ 27 and a waist to height ratio (WHtR) ≤ 0.53 after weight loss may represent clinically meaningful treatment targets for reducing the 10-year risk for obesity-related complications such as type 2 diabetes, hypertension, atherosclerotic cardiovascular disease, and hip/knee osteoarthritis, Johnson noted.
Therefore, her team aimed to assess the comparative effectiveness of an RWL program vs a gradual weight loss (GWL) program in achieving those treatment targets.
To do so, they conducted a 52-week randomized clinical trial — a collaboration between a European Association for the Study of Obesity Collaborating Centres for Obesity Management and a commercial weight-loss provider.
A total of 284 participants (90% women) were randomly assigned in a 1:1 ratio to either a 16-week food-based RWL or GWL program. Participants had a mean age of 48.1 years; weight, 102.4 kg (226 lb); height, 169 cm (5 ft 5 in); BMI, 35.8; waist circumference, 112.7 cm (44 in); and WHtR, 0.67.
The RWL program consisted of the following: weeks 1-8: < 1000 kcal/d; weeks 9-12: < 1300 kcal/d; and weeks 13-16: < 1500 kcal/d. The GWL program consisted of 16 weeks of 800-1000 kcal/d below the participant’s estimated total energy expenditure, calculated by estimating the individual’s resting energy expenditure and adjusted based on if they had low, medium, or high physical activity.
Both groups then followed 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 3 months followed by monthly meetings or individual contacts for the remaining 5 months of the study.
Food composition in both programs was based on current Norwegian dietary recommendations issued by the Norwegian Directorate of Health. Core recommendations included consuming healthy foods such as vegetables, fruits, whole grains, low-fat dairy products, fish, eggs, lean meat, and other protein-rich foods and limiting the intake of saturated fats and added sugars.
The primary outcome was 1-year percent total body weight loss (%TBWL). Post hoc exploratory outcomes were proportions of participants achieving a BMI ≤ 27 or a WHtR ≤ 0.53 after 1 year.
Both Succeed, but Faster Was Better
“In our study, both groups achieved favorable outcomes,” Johnson said. “The main difference between the two groups was the level of energy intake during the initial 16 weeks. An energy deficit remains the fundamental requirement for weight loss, regardless of the approach used — diet, medication, or surgery.”
During the initial 16 weeks, participants in the RWL group lost significantly more body weight than those in the GWL group, with mean %TBWLs of -12.9% and -8.1%, respectively.
At 1 year, the significant difference was maintained, with mean %TBWLs of -14.4% in the RWL group and -10.5% in the GWL group.
The proportion of participants achieving a BMI ≤ 27 was significantly higher in the RWL group than in the GWL group at both 16 weeks (13.8% vs 0.8%) and 1 year (28.3% vs 9.7%). Similarly, a higher proportion of patients achieved a WHtR ≤ 0.53 in the RWL group at 16 weeks (24.2% vs 8.9%) and at 1 year (33% vs 18.4%).
“These findings indicate that when provided within a controlled and professionally supervised setting, RWL may represent a more effective method for attaining anthropometric thresholds associated with reduced obesity-related health risks than GWL,” the authors concluded.
Summing up, Johnson said, “Our results clearly challenge the prevailing belief that slow and steady [GWL] is necessary to prevent weight regain and reduce obesity-related complications. By contrast, we show that [RWL] is not associated with weight regain and, more importantly, that a larger proportion of participants undergoing [RWL], compared with [GWL], achieved clinically meaningful treatment targets for reducing the 10-year risk of type 2 diabetes, hypertension, atherosclerotic cardiovascular disease, and hip/knee osteoarthritis.”
“In an era where medications and surgery dominate the headlines in obesity treatment...our study demonstrates that very good and sustained results can be achieved by using a structured dietary program combined with long-term follow-up not only in terms of weight reduction but also through lowering the risk of obesity-related complications,” she added. “This approach costs only a fraction of pharmacological and surgical treatments and is therefore more accessible to a large number of individuals struggling with obesity.”
Endocrinologist Priya Jaisinghani, MD, an obesity medicine specialist at NYU Langone Health in New York City who was not involved in the study, commented for Medscape Medical News. “We do not want to just focus on speed and quantity of weight loss but other quality metrics. We need more data on body composition changes (fat mass vs lean muscle mass loss), nutritional adequacy, metabolic adaptation, improvement or reversal of weight-related comorbidities, and the addition of obesity pharmacotherapy use, as well.”
Furthermore, she said, “Clinicians should individualize treatment. Not every patient is a candidate for aggressive caloric restriction. We must account for frailty, sarcopenia risk, eating disorder/disordered eating history, comorbidities, medications, nutritional adequacy, and psychosocial factors.”
In real-world practice, she noted, patients may not have access to weekly multidisciplinary visits, close monitoring, or long-term behavioral maintenance programs. In addition, the study cohort was mainly female, and the population may need to be more ethnically and geographically heterogenous to be more generalizable.
“Most importantly, obesity should be treated as a chronic disease requiring long-term management, not simply a short-term weight-loss intervention,” she said. “Behavioral support, physical activity, sleep, nutrition quality, and pharmacotherapy, if applicable, are some factors that may play a role in maintenance.”
The study was equally organized and funded by the Department of Endocrinology, Obesity and Nutrition at Vestfold Hospital Trust and Roede AS. Johnson declared employment at the Department of Endocrinology, Obesity and Nutrition at Vestfold Hospital Trust. Jaisinghani reported receiving fees from Eli Lilly, Novo Nordisk, Madrigal, Corcept, and Boehringer Ingelheim.
