I almost grabbed a 10 lb vest because I figured weight is weight. Then I found a study through the National Library of Medicine that changed my mind. Two groups wore weighted vests daily for three weeks. The group at 11% of their body weight lost significantly more body fat than the group at just 1%.
Same walk. Same duration. The only difference was how heavy the vest was.
Below 10% of your body weight, your body barely registers the load. You wear it for a month, nothing changes, and you blame the vest.
The vest wasn't the problem. The weight was.
Under 130 lb → 12 lb vest
130–175 lb → 16 lb vest
175–200 lb → 20 lb vest
200 lb+ → 30 lb vest
I went with the 20 lb. First walk with it on, I knew immediately I'd made the right call.