In several experiments, subjects were overfed to varying degrees in order to produce weight gain. Here are the results of these experiments

These studies have shown that when overfed, initial body fat level is also important:

Those with an initial body fat content of 10 kg (22 lbs) gained 70% lean mass, and 30% fat mass.

Those with an initial body fat content of 20 kg (44 lbs) gained 30% lean mass, and 70% fat mass.

Those with an initial body fat content of 40 kg (88 lbs) gained 20% lean mass, and 80% fat mass.

These striking differences in the ratio of LBM gained to fat gained illustrate the need to start an overeating phase while lean.

In the leanest subjects, there was a 2 1/3 pound muscle gain for every 1 pound of fat gained.

However, for the fatter subjects, 4 pounds of fat were gained for every 1 pound of muscle gained.