ESPE Yearbook of Paediatric Endocrinology

To read the full abstract: EClinicalMedicine. 2020 Apr 30;22:100338. doi: 10.1016/j.eclinm.2020.100338.

The gravitostat hypothesis was only recently proposed based on studies in rodents showing that the addition of external weights to the body limits the rate of weight gain, independent of leptin signalling. In rodents, this was achieved by inserting weighted balloons into the abdominal cavity (1).

This randomised controlled trial now tested the same hypothesis in human obese adults (n =72), mean age ~50 years, who were assigned to wear a heavy (11% of body weight) or light (1% of body weight) weighted vest for 8 hours each day for 3 weeks. Those who wore the heavy vest lost more body weight than in the light vest group (mean relative difference: -1.4%, 95% CI: -2.0 to -0.8; P =1.5×10−5). Furthermore, changes were seen in fat mass (-4.0%, -6.5 to -1.5; P =1.9×10−3) but not in fat-free mass (0.4%, -1.47 to 2.34; P =0.65).

From a clinical perspective, this seems to be a remarkably simple intervention to recommend. All those in the heavy vest group managed to wear this for at least 6 h per day, except for one person who managed on average 5.99 h/day) and there was no difference between groups in the % time spent standing. Non-serious musculoskeletal adverse events were more common in the heavy vest group (20%; 1 arthralgia, 2 myalgia, 2 pain in lower leg, 2 swelling of ankle and/or foot) than in the light vest group (2.7%; 1 myalgia), but it is possible that these are only short-term effects.

From a biological perspective, this concept is fascinating. It suggests that the homeostatic regulation of body weight involves not just the established system of hormonal feedback from adipose accumulation (e.g. leptin), but also a mechanical sensing of body weight that does not discriminate between endogenous and external loads. How this operates is yet unclear. The previous rodent studies documented no change in energy expenditure but reduced food intakes (1); no such difference was reported here in humans, although the measures of self-reported food intake are much more noisy than animal experimental conditions.

Reference:

1. Jansson JO et al. Body weight homeostat that regulates fat mass independently of leptin in rats and mice. Proc Natl Acad Sci USA. 2018; 115: 427–432.