Isoleucine (symbol Ile or I) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH+3 form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a hydrocarbon side chain, classifying it as a non-polar, uncharged (at physiological pH), aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it, and must be ingested in our diet. Isoleucine is synthesized from pyruvate employing leucine biosynthesis enzymes in other organisms such as bacteria. 

Weight Loss Whilst Maintaining Muscle Mass

A large number of studies have been carried out to prove this fact. Research at University of Illinois on weight loss was conducted. A group was given 10 grams of Leucine per day with 125 grams of protein daily. It was made sure that every single diet has at least 2.5 grams of Leucine content in that. The study results were that higher levels of Leucine helped to lower the weight without muscle breakdown
 

Cholesterol Regulation

"Medicine & Science in Sports & Exercise" conducted a study on rats in May 2009. The study showed that rats that were supplemented with Leucine had increased blood levels of high-density lipoprotein cholesterol (good cholesterol).Rats who were consuming high fat foods were subjected to changes occurring due to Leucine .