The primary endpoint of the study was to demonstrate significantly greater "excess weight loss" (EWL) in the VBLOC treatment group compared to the control after 12 months.
EWL was calculated as a percentage equal to total weight loss in the trial (the numerator) divided by the difference in baseline weight and "ideal weight" using a BMI of 25 (the denominator.)
Initial EMPOWER study results were first reported in 2009 and published fully in
three years later. The EWL for VBLOC-treated patients was 17% compared to 16% for control patients. Clearly, there was no statistically significant difference at all in excess weight loss between the two groups.
EnteroMedics has never disclosed or published actual numerical weight loss data from the EMPOWER study. However, if I use the same 5' 4" woman weighing 240 pounds as a typical patient, a 17% EWL translates into weight loss of 16 pounds, or 6.7% from baseline. That's slightly better than what you'd expect to see from Arena's Belviq but less than Vivus' Qsymia.
The sham device's 16% EWL translated into 15 pounds of weight loss, or 6.3%. [Using our typical female patient as an example, once again.]
EnteroMedics blamed the negative results on the unexpectedly high weight loss in the control group. Somehow, the low-intensity electrical signal of the control VBLOC devices contributed to weight loss, the company said.
Better performance (higher EWL scores) was also correlated directly with increased device usage in both the treated and control patients. Patients who used the active VBLOC device for more than 12 hours per day reported an EWL of 30% compared to 22% for patients using their control devices for more than 12 hours.
EnteroMedics' explanation for the negative EMPOWER study results don't fully gibe with the published data. At various times during the study, control patients lost more weight than actively treated patients. This is particularly true for patients who were more compliant (VBLOC use greater than 9 hours per day) and in patients who lost the most weight.
For instance, 30% EWL was achieved by 28% of VBLOC patients but 37% of control patients. At 35% EWL, the trend reverts back to VBLOC's advantage (23% vs. 20% of patients -- still close.) The same percentage of VBLOC and control patients (18%) achieved 40% EWL.
Looking at the published EMPOWER data, not only was the control VBLOC device active but at multiple times during the study, it was superior to the fully operational (and presumably more effective) VBLOC device. EnteroMedics has never offered an explanation for these data.
A more plausible, logical explanation for the negative EMPOWER results: VBLOC doesn't induce weight loss. Instead, patients who enrolled in the study lost weight through a mixture of placebo effect, adherence to healthier diet and more exercise.
Obese patients willing to have a device surgically implanted are going to be motivated to lose weight -- and they did just that in equal amounts in the treated and control arms of the study overall.