>if we could use leptin to increase dieting efficacy

it's called a refeed and bodybuilders have been doing it for decades to drop fat while maintaining muscle mass, you don't need leptin injections

some recent studies have backed up the bro science as well

>The researchers reported that 19 participants in the continuous diet group completed the study and lost an average of 9.1 kg furthermore, 17 participants in the intermittent diet group completed the study and lost an average of 14.1 kg (4).Hence, the authors concluded that greater weight and fat loss was achieved in the intermittent diet group (4)