[prostoalex]

While you can control the input, the output gets harder - one cannot just simply double/triple their defecation rate, and exercise tends to work out an appetite.

http://well.blogs.nytimes.com/2014/11/12/exercising-but-gain...

Output is governed by hormones, and the only reliable hack for now seems to be significantly lowering insulin by switching to ketogenic diet (or a variation thereof, /r/zerocarb, /r/keto, Atkins, Dukan). I'd recommend this book https://en.wikipedia.org/wiki/Good_Calories,_Bad_Calories with understanding that a lot of nutrition and diet science is in very premature stage because of World War 2 and lack of funding thereafter.