The latest weight loss hack is not a pill or a diet, but rather a clever trick that plays with gravity itself.

Researchers are investigating the ‘gravitostat theory,’ which proposes that the body possesses an internal scale that detects weight. By using a weighted vest to add external weight, individuals can potentially convince the body to adjust its metabolism to burn more fat.

This idea, made popular by a fictional anime hero from Dragon Ball who trained under extreme gravity to grow stronger, is now receiving scientific support.

Recent studies have indicated that bones act as weight sensors. When they perceive an increased load, they notify the brain to initiate metabolic shifts that may lead to fat reduction.

In a self-experiment detailed in his new book, Pull: How Gravity Shapes Your Body, Steadies the Mind, and Guides Our Health, Dr. Brennan Spiegel wore a weighted vest and ankle weights totaling 40lbs for eight weeks without altering his diet or exercise routine.

By donning a weighted vest, Spiegel, who is the director of health services research at Cedars-Sinai Medical Center in Los Angeles, claimed he enhanced the gravitational force on his body, leading it to believe he was heavier. This activated a biological response that aided in weight loss without needing to use a treadmill.

He remarked, ‘This is believed to induce changes in appetite, metabolism, and even the amount of fat stored in the body. It’s like having a hidden weight-loss coach inside your bones.’

The results were striking: he lost weight and significantly improved his cardiovascular fitness, as the heart and lungs had to adapt to the increased demand. He also saw a significant reduction in chronic neck pain. 

In a self-experiment, Dr Brennan Spiegel (pictured) wore 40lbs of weights for eight weeks. By tricking his body into feeling heavier, he triggered a biological response that led to weight loss without dieting or extra cardio

This approach, often referred to as ‘rucking’ when done with a backpack, transforms everyday activities into low-impact, resilience-boosting, strength-building exercises by harnessing gravity.

Spiegel, who runs regularly and is not overweight, said: ‘One unexpected outcome was my weight. Without trying to lose weight, I found myself 4lbs lighter by the experiment’s end. Without running or changing my diet, this was an unexpected bonus.

‘After eight weeks… I emerged stronger and fitter, with diminished pain and better gravity resilience.’

His experience aligned with formal studies, including one from the University of Gothenburg published in 2020. 

In that trial, adults with obesity wore a vest corresponding to 11 percent of their body weight for at least eight hours per day for three weeks, while a comparison group of obese people wore a vest corresponding to one percent of their body weight.

After just three weeks, the group wearing the heavier vests lost an average of about 3lbs (1.38 kg), and reduced their body fat mass by over four percent.

In contrast, the weight loss in the light-vest group was not statistically significant.

Scientists proposed a gravitostat system where the bones in the lower limbs sense how much weight they are carrying. 

When they detect a heavier load, such as when wearing a weighted vest, they send signals to the brain, which then triggers the body to lose fat mass and return to a manageable total weight.

Added weight increases the body’s energy expenditure because the muscles must work harder to move the greater mass against the pull of gravity. 

This is especially true for movements against gravity, such as standing up or walking uphill, where the energy cost is directly proportional to one’s total mass.

Scientists believe leg bones sense when the body is carrying extra weight and signal the brain to shed fat to lighten the load (stock image)

Spiegel said in his book: ‘By understanding and leveraging the gravitostat, we can develop new strategies for weight management and overall health. 

‘My own experience with a weighted vest aligns with this theory, showing how gravity and mechanical loading can influence our bodies in surprising ways.’

During Spiegel’s self-experiment, his back was the first to protest under the added weight, while the ankle weights made his calves and thighs tire with every step. 

By the end of the day, his feet were cramped while his heart beat faster than usual. He also developed a subtle headache, particularly in the back of his head.

After a difficult start, his body began to adapt, however. The initial aches, soreness and headaches faded and gave way to newfound strength and resilience. His chronic neck pain improved, leaving him feeling more ‘vibrant.’

He said: ‘To quantify the effects, I turned to some good old-fashioned number crunching.’

For two months, Spiegel tracked key metrics, including his maximum squat count, recovery time after climbing 50 stairs, and his VO2 max, the body’s peak oxygen use during intense exercise, during a one-mile run. 

Pull by Dr Brennan Spiegel argues that gravity is a crucial, overlooked force shaping people’s physical and mental health

This data-driven approach, which he called ‘Operation Gravitate,’ provided clear, quantifiable evidence of his progress.

The data showed dramatic improvement. 

Initially, 73 squats spiked his heart rate to 124 beats per minute (BPM), with a slow recovery. 

After eight weeks, Spiegel could perform over 200 squats with a lower peak heart rate (115 BPM) and a recovery time cut in half. 

A lower heart rate during exercise means the body has become a more efficient, powerful, and resilient machine. It can do more work with less effort and recover from stress much faster. 

Similarly, he went from being winded after climbing stairs to finishing with controlled breathing and no need to rest.

Weighted vests are not without risks, however. 

The primary danger of weighted vests is the compressive stress placed on bones and joints, unlike the intermittent load of weightlifting, which can lead to overuse injuries.

The added load particularly stresses the spine, knees, hips, and ankles, risking new injuries like plantar fasciitis or aggravating conditions like arthritis. It can also magnify postural imbalances and is risky for those with osteoporosis or heart conditions. 

To start, experts recommend a very light weight, around five percent of body weight, for short, dedicated exercise sessions, not daily chores. The focus must be on maintaining good form; if the vest causes hunching or alters your gait, it is too heavy.

Spiegel’s discovery explains the science behind a powerful real-world weight management tool, ‘rucking,’ or walking with a weighted backpack.

This military-born practice is effective because it directly engages the body’s gravitostat, turning a simple walk into a potent metabolic workout.