These enzymes included the lipase inhibitor associated with a reduction in lipid absorption for the treatment of obesity, inhibition of the carbohydrate-digesting enzymes, α-glucosidase and α-amylase, as an approach to control diabetes, and inhibition of the neurotransmitter-degrading enzymes, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), as well as the amyloid precursor protein (APP)-degrading enzyme β-secretase (BACE-1), in Alzheimer’s disease (AD). Here, APP is linked to obesity due to melanocortin 4 receptor deficiency.