Yo-yo effect

Up to 80% of people who follow a strict weight loss diet end up regaining weight. Many of these people return to their starting weight within one or two years. The underlying causes of this yo-yo effect were previously ascribed to factors like lifestyle and living conditions. In addition to psychosocial factors, adipose tissue also increases the chance of future weight gain. Mariman's team examined the adipose tissue of people who gained weight after weight loss. An analysis of this tissue revealed that immune cells, more commonly known as white blood cells, also play a significant role.

White blood cells

We have known for some time now that white blood cells, or leukocytes, penetrate adipose tissue and make it more aggressive in people who are overweight. After weight loss, these leukocytes should become less active, and they do in some people. But in others, the leukocytes remain extremely active in the adipose tissue, as the Maastricht research team discovered. These people have a considerably higher risk of gaining weight in the future. ‘Follow-up research should reveal how this mechanism works,' says Mariman.

Stress in fat cells

Mariman suspects he knows why the predictive value of white blood cells can lead to weight gain. 'Fat cells play an important role in weight loss and weight gain. Fat cells release more than 500 different protein hormones. One of these important proteins is leptin, which supresses appetite and is also involved in inflammatory response. When someone loses weight, fat cells shrink and leptin levels decrease. Shrinking fat cells paired with a disrupted energy balance causes stress within the fat cells. The body may mistake this stress response for inflammation,' says Professor Mariman. 'That could explain why some people have increased white blood cell activity in adipose tissue after weight loss. This insight may help to minimise inflammatory response, thereby helping people control the yo-yo effect and maintain their goal weight.'