For years, doctors and dietitians have been repeating the same advice: weight loss should be slow, gradual and steady, to avoid regaining it. But a new Norwegian study, presented at the European Congress on Obesity (ECO) in Istanbul, is challenging this decades-old belief.
According to researchers, rapid weight loss not only brings better results in a shorter time, but also seems to help maintain them in the longer term.
The research was conducted by Line Kristin Johnson and her team from the Department of Endocrinology, Obesity and Nutrition at Vestfold Hospital Trust in Tønsberg, Norway. The authors argue that the idea that “slower weight loss is better” has been based largely on limited or observational studies, while randomized clinical trials have been scarce.
The study was also based on the results of an Italian study published in 2025, according to which achieving a BMI below 27 and a waist-to-height ratio below 0.53 significantly reduces the 10-year risk of type 2 diabetes, hypertension, and cardiovascular disease.
To understand which method works best, researchers followed 284 adults with obesity and a BMI over 30 for 52 weeks. Participants were divided into two groups.
The first group followed a more aggressive regimen: less than 1,000 calories per day during the first few weeks, with a gradual increase in calories by the end of the 16-week program. The second group followed a more traditional and moderate approach, with a lower calorie deficit.
After four months, the results were clear. The rapid weight loss group lost an average of 12.9% of their body weight, while the gradual group only lost 8.1%.
But what surprised the researchers was that the difference remained noticeable even after a year. Participants who had lost weight quickly maintained better results: 14.4% weight loss versus 10.5% in the gradual group.
Clinical outcomes were also more positive. Nearly a third of participants in the first group achieved a BMI below 27 after one year, compared with less than 10% in the second group.
After the initial phase, both groups followed the same weight maintenance program, with professional consultation and support. The diet used was based on regular food and healthy dietary recommendations: vegetables, fruits, whole grains, fish, lean meats, and a reduction in sugars and saturated fats.
The authors emphasize that rapid weight loss should be achieved in controlled conditions and under professional supervision, but according to them, the results clearly challenge the traditional belief that slow diets are necessarily more sustainable.
"Our results show that rapid weight loss is not associated with greater weight regain and, instead, helps more people achieve clinically important goals for reducing the risk of diabetes, hypertension and cardiovascular disease," Johnson said during the study presentation.
