by University of Gothenburg

Credit: RDNE Stock project from Pexels

Having lost a great deal of weight appears to offer some protection against ill health even for those who have regained some of their weight loss. This is shown in a study at the University of Gothenburg of people who have undergone weight-loss surgery.

The study, published in The Lancet Region Health—Europe, focuses on the health consequences of regaining some weight following significant weight loss, an area in which scientific knowledge is described as extremely limited.

The study analyzed mortality, cardiovascular disease, cancer, and microvascular disease, which affects the body’s smallest blood vessels, in people who had initially lost a great deal of weight and then regained a substantial amount.

The study included 1,346 participants from the SOS (Swedish Obese Subjects) study at the University of Gothenburg, the world’s most comprehensive study of the long-term effects of bariatric surgery compared to conventional obesity treatment. Additional health data on the participants were retrieved from several national registries held by Sweden’s National Board of Health and Welfare.

Same cancer risk and life expectancy

One year after surgery, the participants had lost an average of about 30 kilograms. Four years after the procedure, just over half of them had regained at least 20% of the weight lost during the first year.

Changes in body mass index, both absolute (A) and relative (B), over 20 years following bariatric surgery for the weight regain and weight maintenance groups. Credit: The Lancet Regional Health – Europe (2025). DOI: 10.1016/j.lanepe.2025.101261

Accordingly, the researchers compared two groups: one in which the participants had regained at least 20% of their earlier weight loss, and one in which the participants had maintained their lower weight or gained only a little.

In terms of cancer risk and life expectancy, no differences were found between the groups. Cancer incidence and mortality remained at the same levels regardless of partial weight regain. However, differences were observed regarding microvascular disease, with those who regained weight being at greater risk. The incidence rate was 11.0 per 1,000 person-years, as compared to 8.7 in the group that maintained their lower weight.

A similar pattern, albeit less distinct, was seen for cardiovascular diseases (heart attack, stroke, and heart failure combined). The incidence rate was 15.7 per 1,000 person-years in those who had regained a lot of weight, as compared to 13.0 in the group who had maintained their lower weight.

Long-lasting positive effects

One of the lead researchers behind the study is Kajsa Sjöholm, an associate professor at the Department of Molecular and Clinical Medicine at Sahlgrenska Academy at the University of Gothenburg:

“Until now, the effects of weight regain following major weight loss on long-term health and mortality have remained unknown. What we’re now seeing is that even those who regain some of their weight loss experience long-lasting positive effects with the same life expectancy as those who maintain their lower weight,” she says.

“As for cardiovascular disease, we see that weight regain worsens the risk factors, underlining the need for patients to receive effective support to prevent significant weight gain. Weight regain also leads to other challenges that can reduce quality of life, such as hip and knee pain and the stigma associated with obesity,” says Sjöholm.

More information: Lena M.S. Carlsson et al, Health outcomes and their association with weight regain after substantial weight loss in Sweden: a prospective cohort study, The Lancet Regional Health – Europe (2025). DOI: 10.1016/j.lanepe.2025.101261

Provided by University of Gothenburg

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