Nutrient supplementation alone will not have a big impact on increasing lean mass. You may be able to reduce body fat which will increase the percentage of lean mass with nutritional supplementation alone. A stimulus to build muscle mass, such as resistance training, will be needed to actually add lean mass of any significant amount. Even with regular resistance training and healthy diet, increases in lean mass are not generally rapid (may take several months).

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Exercise and body building (non-aerobic exercises) with a suitable diet can help us gain weight. "L-Carnitine" and "Wey Protein" are the most popular supplement for gaining lean body mass.

A healthy brain tends to auto-regulate body composition through a broad range of caloric intake. Sugar, HFCS, high glycemic carbohydrates especially from grains and excessive omega 6 fatty acids are the primary components of processed food. These dietary elements also tend to be obesogenic and they are also known to adversely affect brain function.

Eating a healthy, whole foods diet and avoiding processed food is the best way to maintain a healthy body composition. Strength training will tend to enhance lean body mass.

Callisthenics is a good form of exercises that helps to stimulate lean muscle growth, results can be moderately rapid if put in combination with a healthy diet and sufficient sleep, as it allows the body to recover.