Jakob Bellman – Health Effects of Weight-Loading in Obesity

Opponent and examining committee

Opponent: Professor Tommy Olsson, Department of Public Health and Clinical Medicine, Umeå University, Umeå

Examining committee: Professor Lars Westberg (chair), Professor Robert Jan Brummer (ÖrU) and Associate Professor Rauni Rossi Norrlund

Good to know

The disputation is held in English

Welcome to attend online via streaming, via Zoom Webinar: link to be announced

Chairperson of the disputation: Professor Eric Hanse

Less fat and more muscle – with a weighted vest

Obesity is one of the major public health challenges of our time and raises the risk of type 2 diabetes, cardiovascular disease, fatty liver disease, and several cancers. It is increasingly clear that health depends not only on how much a person weighs, but on body composition – the balance between fat mass and lean mass.

Modern anti-obesity medications and bariatric surgery reduce body weight effectively, but they generally reduce fat mass and lean mass together. At the same time, sedentary living has substantially reduced the mechanical load carried by the human skeleton compared with the conditions under which our physiology evolved.

This thesis asks what happens when part of that load is restored. In the main clinical trial, adults with obesity were randomly assigned to wear either a heavy weighted vest, corresponding to about eleven percent of body weight, or a light control vest, for roughly eight hours a day over five weeks. The heavier vest reduced fat mass and waist circumference and increased lean mass. The central effect was therefore an improved balance between fat and lean mass – a better body composition. The changes occurred even though participants spent more time sedentary, and without any measurable change in energy expenditure.

Three further studies examined what happens in the tissues themselves. PET imaging showed increased glucose uptake in muscle, bone, and bone marrow of the loaded legs. Cardiac workload rose while the vest was worn, and the effects on autonomic regulation were largely confined to the hours of loading. An experimental animal study argued against altered fluid or salt balance as an explanation.

Together, these findings suggest that weight-loading acts as an independent physiological signal that can shift the balance between fat and lean mass. Weighted vests may therefore complement existing obesity treatments and inform future strategies focused on improving body composition rather than reducing body weight alone.