Last Updated on October 6, 2025 by Kayla
Losing weight is one thing. Keeping it off is another challenge entirely. Most of us have experienced the frustration: the scale goes down for a while, but sustaining those results can feel like an uphill battle.
Ever wonder why weight regain feels inevitable? The “gravistat” hypothesis may explain it—and might motivate you to wear a ruck or weighted vest for more than just walks!
The Gravistat Hypothesis
Similar to how a thermostat controls temperature, imagine your body’s “gravistat” as a control for weight.
When you lose weight, your bones and other cells “sense” the change and trigger compensatory mechanisms—like increased appetite and lower energy expenditure—to push your weight back to its previous set point.
In other words, your body actively works to resist weight loss, making it difficult to maintain long-term. A recent study put this theory to the test.
The Study: Medifast vs Medifast + Weighted Vest
Older adults with obesity were assigned to one of two groups: a low-calorie diet (Medifast) or Medifast + weighted vest for 6 months.
Vest users were asked to wear the vest for up to 10 hours during the most active part of their day; the average daily vest use was approximately 6 hours. The amount of weight worn matched the amount of body weight lost.
Here’s what they found:
- Both groups lost ~23 pounds and similar amounts of muscle.
- Diet-only group: regained almost all the lost weight over 2 years.
- Diet + vest group: regained only about half the weight and preserved resting metabolic rate (RMR).
So what does this study tell us?
Wearing a weighted vest seemed to offset the drop in metabolism that usually follows weight loss, supporting the gravistat hypothesis.
While the study isn’t perfect, it shows an important principle: strategies that protect metabolism make weight maintenance easier.
Want to learn more?
I recently appeared on two podcasts, sharing about the benefits of rucking for women. We discuss sustainable nutrition strategies as well as the differences and advantages of wearing a weighted vest versus a rucksack. Learn more and listen here:
- Learning to Glow: Rucking for Women’s Strength, Energy, and Longevity with Kayla Girgen
- The Bomb Life: Shut the Ruck Up! Walking to Build Real Strength with Kayla Girgen
If you haven’t already, be sure to pre-order Ruck Fit: Build Strength and Endurance by Walking with Weight, which will be released January 2026!
Helping women lose weight without eating “perfect.” Learn how to balance blood sugar, build strength & overcome all-or-nothing thinking! Apply to learn more!
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