Clinical trial suggests rapid weight loss is more efficient and sustainable than a gradual approach

A clinical trial has found that rapid weight loss is more effective than gradual weight loss in terms of losing weight and keeping it off. The results were presented at the 2026 European Congress on Obesity (ECO) held May 12–15 in Istanbul, Türkiye. 

The findings contradict the common belief that rapid weight loss is unhealthy and increases the likelihood of weight regain.

Over 52 weeks, the research team assessed the effectiveness of a rapid weight loss program versus a gradual one. The investigator-initiated, randomized, clinical trial was in a partnership between the Department of Endocrinology, Obesity and Nutrition, Vestfold Hospital Trust, and Roede, a Norwegian provider of commercial weight-loss programs. 

Nutrition insight sits down with the study’s lead author, Dr. Line Kristin Johnson from the Vestfold Hospital Trust, Tønsberg, Norway, to discuss how these findings contradict common knowledge, and how nutrition and food-based interventions play a significant role in weight loss.

She tells us the findings are highly relevant in the era of GLP‑1 receptor agonists. “GLP‑1 drugs produce relatively rapid weight loss as they help people eat less, similar in scale to intensive dietary interventions. Importantly, this positions dietary programs as a complement or alternative to GLP‑1 therapies, especially where access, cost, or tolerability are limiting factors.”

“I believe it is important to bear in mind that, as GLP‑1 therapies reshape expectations, the nutrition field has a unique opportunity to deliver clinically meaningful results through structured, accessible, and widely applicable interventions.”

Sustainable weight loss

The study included 284 obese adults, of which 90% (257) were women. The participants were randomized into two groups. One group followed a 16-week food-based rapid weight loss program: eating 1,000 calories daily between week one and eight, 1,300 calories daily between week nine and 13, and 1,500 calories daily between week 13 and 16. 

The other group followed a 16-week food-based gradual weight loss program by cutting calories by approximately 800–1,000 per day, while the self-reported intake of this group was approximately 1,400 calories daily.

After the initial 16 weeks, the participants from both groups entered the same 36-week weight-regain prevention program.How many calories were burned was not calculated, but based on an estimate of the participants’ physical activity levels.

After the 16 weeks, the participants from both groups entered the same 36-week weight-regain prevention program: weekly weight-loss group sessions from week one to 16, followed by in-person group meetings every 14 days for the first three months, and then monthly meetings for the last five months. 

The participants were advised to increase their daily intake by 100–300 calories daily to stabilize their weight, which were later adjusted based on needs. The participants could choose if they wanted to maintain their current weight or keep losing weight, and most opted for the latter.

“The results demonstrate that individuals who lost weight rapidly did not regain more weight than those who lost gradually, when both groups received comparable follow-up care. In fact, on average, participants in both groups did not regain weight at all, but they continued to lose weight over time,” explains Johnson.

Weight maintenance support

The findings directly challenge the long-held assumption that gradual weight loss is inherently more sustainable, she says. “Traditionally, slower weight reduction has been thought to promote better behavioral adaptation and minimize weight regain.”

“However, our data suggests that a 16-week calorie-restrictive rapid weight loss program, when followed by a weight regain prevention program every other week (week 17–28) and monthly (week 28–52), does not result in greater weight regain, and may enable more individuals to achieve meaningful risk reduction targets.”

She argues these results could support a shift toward nutrition programs that emphasize an effective weight-loss phase followed by comprehensive behavioral support to prevent weight regain.

Total weight change during follow-up was similar between groups, indicating no inherent physiological “penalty” associated with rapid loss. Moreover, participants in the rapid weight-loss group achieved greater initial weight reduction, resulting in a larger net loss at follow-up.

“These findings suggest that rapid weight loss can be sustainable when delivered within a comprehensive weight-management framework that includes structured, frequent (every two weeks to monthly) maintenance support sessions.”

GLP-1 alternatives

Johnson also highlights what opportunities this study creates for commercial weight-management companies and functional ingredient suppliers targeting consumers who cannot access GLP-1 drugs or bariatric surgery. 

Johnson highlights what opportunities this study creates for commercial weight-management companies and functional ingredient suppliers.“These findings may still be valuable for informing the design of clinically guided rapid weight-loss programs for individuals seeking ‘GLP‑1–like’ results without pharmacological intervention.”

“Such approaches could also serve as a complement or alternative to GLP‑1 therapies, particularly in settings where access, cost, or tolerability present challenges.”

GLP-1 use is gaining popularity, expanding the market opportunity for complementary nutritional products. As the weight-loss drug interferes with hunger cues, leading users to eat less overall, experts have previously urged users to follow nutritional guidance to avoid micronutrient inefficiency, loss of lean muscle mass, and other potential long-term health impacts.

Nutrition Insight recently sat down with experts from Ingredion, Fonterra, and Carbery to explore new innovation opportunities for the nutrition industry as GLP-1’s are reshaping demands. Consumers seek more nutrient-dense products to fill the potential gap of eating sufficient protein, fiber, and vitamins as hunger decreases as a result of the medication. 

Nutritional strategies

Sticking to a nutritional strategy is crucial to maintain lost weight after discontinuing a diet, weight loss program, or weight loss medication. 

Johnson comments on which nutrients are most important in this stage of the weight loss journey. 

“Maintaining lean mass, satiety, and adherence during rapid calorie restriction depends on several core strategies,” she highlights. “I would highlight the importance of adequate protein intake, a high intake of dietary fiber, ensuring micronutrient and essential fatty acid adequacy, and structured meal planning.”

“In addition, aerobic physical activity and resistance training may be added to regulate appetite, improve sleep, and prevent muscle mass loss in the weight maintenance phase.”

She says there is no such thing as a “one-size-fits-all” approach in any context. However, regardless of the strategy chosen, achieving a calorie deficit is essential for weight loss.

“With rising obesity-related health care costs, clinically supervised rapid weight-loss programs could become an increasingly important component of population health strategies,” says Johnson.

“Potential developments may include greater integration into primary care and community health systems. While I am cautious about speculating on the role of the nutrition industry, one possible avenue could be the delivery of models that combine in-person care with digital and remote support solutions.”