Losing weight can improve blood pressure, blood sugar and reduce joint pain.

Weight loss comes with an unintended consequence, however — bone loss. For older adults especially, shedding pounds also means losing bone mineral density (BMD), raising the risk of fractures and disability.

When we carry extra body weight our skeleton adapts to support it. But when that weight disappears, bones experience less mechanical stress, and the body responds by reducing bone density.

Why is bone density affected by weight loss? Our bones respond to the loads placed upon them. When we carry extra body weight our skeleton adapts to support it with added bone density. But when that weight disappears and bones experience less mechanical stress, the body, ever efficient, responds by reducing bone density.

Researchers at Wake Forest University in North Carolina had found that wearing a vest that replaces the pounds lost essentially “tricks” the body into sensing that the load is still there. Weighted vests can help bone health by making up for the weight lost.

Replacing that weight with a weighted vest can preserve muscle and bone and help prevent the metabolic slowdown that accompanies weight loss — both of which are critical as we age.

The study used data from the university's INVEST in Bone Health randomized controlled trial. That larger trial, led by colleague Kristen Beavers, PhD, examined whether wearing a weighted vest could help preserve bone mineral density during a year-long weight-loss program in older adults.

In a recent follow-up study, participants were randomly assigned to one of three groups to better zero-in on what was behind the improvement. The three groups included:

  • A weight-loss only group
  • A weight-loss plus resistance-training group
  • A weight-loss plus weighted-vest group

People in the vest group were instructed to wear the vest at least eight hours a day, with the weight gradually increased to match the pounds they had lost.

Using activity-tracking technology, researchers also carefully monitored how much time participants spent upright — standing or stepping. This detail turned out to be crucial.

People in the weighted-vest group who spent more time upright experienced positive changes in bone mineral density. In other words, standing and wearing the vest appeared to stimulate bone preservation, and possibly growth.

In contrast, among those who lost weight and did not wear a weighted vest, spending more time upright was actually associated with negative changes in bone mineral density. Without the added load, simply moving more did not protect bone during weight loss.

Meanwhile, in the group combining weight loss and resistance training, time spent upright didn't influence bone mineral density. Resistance training itself likely provided enough mechanical stimulus to support one's bone health, regardless of standing time.

The takeaway is this: The vest works but only if you're using it while upright and active.

Lead author of the current study, Jason Fanning, PhD, an associate professor of health and exercise science at Wake Forest, explained in a media release, “If we're going to be putting vests on people, we need to train those people to be up and moving. A vest can be a great tool. But, like any tool, it's not going to do the work for you.”

That statement underscores the study's most important message, which is that passive use of a weighted vest isn't enough. Sitting for hours in a weighted vest won't deliver the same benefit as wearing it while standing, walking or performing daily tasks.

Sitting for hours in a weighted vest won't deliver the same benefit as wearing it while standing, walking or performing daily tasks.

For older adults trying to lose weight safely, this finding is particularly meaningful. Age-related bone loss already increases fracture risk. And with weight-loss-related bone decline, vulnerability rises further. A simple non-pharmocological tool like a weighted vest could offer protection, especially for individuals who may not be able to engage in high-intensity resistance training.

The bone-density improvements seen in active vest wearers were promising enough that the researchers are designing a new study to determine whether intentionally encouraging more movement can further boost the vest's effectiveness.

In the meantime, this study reminds us that our bodies are built for motion. The vest may supply the weight, but it's movement that makes it effective medicine.

The study is published in Frontiers in Aging.