As difficult as it may be to lose unwanted body fat, many find that keeping it off long-term is even more challenging. Our bodies interpret a decline in fat stores as a threat to survival and have evolved several mechanisms to prevent further weight loss. Multiple neural and endocrine signals kick in with a vengeance to increase appetite, decrease our desire for physical activity, and increase metabolic efficiency. These negative feedback signals become stronger in proportion with the degree of weight loss and can make it very difficult to continue losing weight or even maintain the fat loss that you’ve already achieved.
But might there be a way to trick the body into turning off these compensatory mechanisms? A fairly recent theory suggests that the addition of external weight—for instance, in the form of a weighted vest—might help to dampen the body’s perception of weight loss, thus mitigating the powerful signals driving weight regain. This possibility was recently put to the test in a study using weighted vests in obese individuals undergoing weight loss.1 Does this added, artificial “body weight” impact weight loss maintenance?
The “gravitostat” hypothesis
The motivation behind the current study lies in a relatively new theory known as the “gravitostat” hypothesis.2 This theory posits that weight loss is sensed by bone cells in the lower extremities as a reduction in gravitational loading—in essence, less body weight means less force transmitted to the ground. These cells then signal to the brain, which responds by increasing appetite and decreasing energy expenditure to prevent further decreases in body weight.
If true, this hypothesis would suggest that we might be able to trick the body into thinking it hasn’t lost significant amounts of its energy reserves simply by adding external weight in order to make up for the gravitational difference caused by the loss of fat. Without the loss of gravitational load, we might at least partially block the regulatory mechanisms designed to promote weight regain. Or so goes the theory.
What they did
To assess this intriguing implication of the gravitostat hypothesis, researchers DeLong et al. investigated the effect of weighted vests on weight loss maintenance in older (65–79 years), sedentary adults with obesity (BMI>30). Participants were randomized to either a weight loss only group (WL, n=17) or weight loss plus daily use of a weighted vest (WL+WV, n=20) for a period of six months. During this time, all participants also followed a very low-calorie diet of ~1100-1300 kcal/day to induce weight loss. WL+WV subjects were instructed to wear the vest up to 10 hours per day (minimum: 5 hours/day) and record daily use in a journal. The weight of the vest was increased each week to compensate for weight loss, up to a maximum of 15% of the individual’s starting body weight.
Body mass, estimated resting metabolic rate (RMR), and body composition were assessed at baseline and at the end of the 6-month intervention, as well as 18 months after cessation of both calorie restriction and the use of the weighted vest (i.e., 24 months from the study start).
What they found
The WL and WL+WV groups lost statistically equivalent amounts of weight by the end of the 6-month weight-loss phase, with an average change of -10.3 kg (-22.7 lbs; 95% CI: -13.7, -6.8 kg) and -11.2 kg (-24.7 lbs; 95% CI: -14.6, -7.7 kg) in body weight for the two groups, respectively. Both groups also lost similar amounts of lean mass, with average changes of -2.8 kg (-6.2 lbs; 95% CI: -3.8, -1.8 kg) and -3.0 kg (-6.6 lbs; 95% CI: -4.0, -1.9 kg), respectively. Thus, the use of a weighted vest during active weight loss did not appear to have a substantial impact on body composition changes experienced during calorie restriction.
However, by 24 months (18 months after the end of calorie restriction and vest use), a significant divergence was observed between groups. While the WL group had regained all lost bodyweight (+0.9 kg/2 lbs from baseline; 95% CI: -3.9, 5.8 kg), the WL+WV group had only regained slightly more than half of the lost weight (-4.8 kg/-10.6 lbs from baseline; 95% CI: -9.6, 0.1 kg).
Perhaps most strikingly, despite the equivalent weight loss during the diet phase, RMR after 6 months of diet declined by just -16 cal/day in the WL+WV group (95% CI: -100.8, 68.2), compared to a drop of -238 cal/day in the WL group (95% CI: -321.9, -153.0). RMR is highly dependent on total body mass, with muscle tissue consuming far more energy than adipose tissue even at rest, so any amount of weight loss—whether primarily due to fat loss or lean mass loss—is generally accompanied by a corresponding decrease in RMR. The fact that RMR did not decrease in the WL+WV group, despite a 25-lb drop in total body weight, is therefore quite remarkable. This indicates that the addition of the weighted vest did indeed offset the reduction in resting energy expenditure typically seen with loss of fat mass.
By 18 months post-diet, RMR had returned to near-baseline in both groups, -9.4 cal/day and -3.5 cal/day for WL and WL+WV, respectively. This was to be expected for the WL group, as they had regained their baseline weight by this timepoint, but is more surprising in the WL+WV group, which remained reduced in weight. (It bears note, however, that all 24-month follow-up data are from subjects who voluntarily returned for testing, which was only around half of the original subjects in each group.)
Not a smoking gun for a “gravitostat”
The much smaller decline in RMR at 6 months in the WL+WV group—and the fact that this group experienced less weight regain after cessation of calorie restriction—would seem to suggest that the addition of external weight prevented or mitigated the strong compensatory responses that typically accompany weight loss. In other words, DeLong et al.’s results appear to support the gravitostat hypothesis, but a closer look leaves significant room for doubt.
The fact that the use of a weighted vest almost entirely suppressed diet-induced reductions in RMR is significant, but we must keep in mind that both groups lost similar amounts of total body weight and lean mass. This means that although the WL+WV group may not have shown increased metabolic efficiency in RMR, they must have experienced some other shift in the balance of “calories in” vs. “calories out” that would prevent them from losing more weight than the WL group. One possibility is that they simply ate more. While the authors prescribed a uniform level of calorie intake for both groups, they don’t indicate that they monitored dietary compliance throughout the study, so the WL+WV group may very well have deviated from the protocol and eaten more than the WL group, which might suggest that they experienced more of a compensatory increase in appetite.
But it’s also possible that the WL+WV group did indeed experience a drop in energy expenditure—it just wasn’t apparent in RMR. RMR is an estimate of how much energy the body consumes at rest to support basic metabolic functions, but it does not include the energy expended for exercise or basic physical activities of daily life. Techniques that can estimate total daily energy expenditure were not employed in this study, so we cannot know whether participants in the WL+WV group may have demonstrated greater metabolic efficiency during activity, thus reducing their total energy demand. Likewise, the requirement for wearing a weighted vest may have led this group to drastically reduce their physical activity due to the added strain caused by the weight, and this, too, could easily contribute to an overall reduction in energy needs without necessarily necessitating a reduction in RMR. In all, the limited metrics in this study mean that we can only speculate on the causes of such large differences in RMR without associated differences in weight changes.
But what can we make of the fact that the WL+WV group only regained about half the weight that was lost after the diet phase ended, compared to full weight regain in the WL group? It’s worth reiterating that the 24-month sampling only included about half of the original study participants, so it is possible that the observed difference in weight regain, or lack of a difference in RMR at 24 months, would look quite different with a full study sample. Yet even beyond this concern, these results still don’t quite add up.
If participants stopped wearing weighted vests after six months but remained weight-reduced, what would stop the body from sensing deloading during the post-intervention stage? The authors propose no mechanistic explanation as to how the effects of the weighted vests might persist for over a year after cessation of use. A more plausible explanation could be that participants’ choices with respect to calorie intake and activity level during and after the intervention may have been biased by the knowledge of the group they were in. After all, this study could not be conducted in a blinded manner, and neither diet nor physical activity was monitored. It’s entirely possible that those who knew they were in a group that “should” keep weight off were biased toward choices that made that very outcome more likely.
All together, these results remain inconclusive due to potential confounding variables, and they aren’t fully consistent with what we would expect with the gravitostat hypothesis. So although they may provide some interesting fodder for future study, they are hardly a smoking gun to validate this new-kid-on-the-block theory about body weight regulation.
The bottom line
The shortcomings of this study prevent us from concluding that weighted vest use can help with maintenance of fat loss or avoidance of weight loss-attributed declines in RMR, though they should not be taken as a reason to discount the many other potential benefits of weighted vests. Much like ruck sacks, these products can serve as conditioning tools for both aerobic and anaerobic training, for strengthening upper back musculature and improving postural control, and as weight loss aids by increasing energy expenditure.
But when it comes to providing validation for any potential “gravitostat” mechanism for body weight regulation, this study adds very little to the limited body of evidence that preceded it. At present, the alternative “lipostat” model—which maintains that the body defends a certain level of fat mass, rather than gravitational force—is more established and has far more support. (For those interested, this model was discussed in greater depth in my previous podcast interviews with Drs. Rudy Leibel and Stephan Guyenet.) Yet we know that the human body often has multiple, overlapping pathways for accomplishing vital goals such as the avoidance of starvation, and future research may indeed uncover a role for a “gravitostat” in conjunction with other weight regulation mechanisms.
Until then, whether you’re trying to lose weight or merely add a little extra to your training routine, weighted vests remain a valuable tool for improving body composition and achieving fitness goals—whether through a gravitostat mechanism or otherwise.
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References
- DeLong C, Nicklas BJ, Beavers DP, Fanning J, Beavers KM. Does weighted vest use during weight loss influence long-term weight loss maintenance? A pilot study in older adults living with obesity and osteoarthritis. Int J Obes (Lond). Published online May 11, 2025:1-4. doi:10.1038/s41366-025-01795-5
- Jansson JO, Palsdottir V, Hägg DA, et al. Body weight homeostat that regulates fat mass independently of leptin in rats and mice. Proc Natl Acad Sci U S A. 2018;115(2):427-432. doi:10.1073/pnas.1715687114
