The goal of anyone who engages in resistance training is to gain added muscle mass and strength. While losing excess body fat mandates a reduction in total calorie intake to the extent that you are consuming fewer calories than you burn through physical activity, gaining muscle more often requires the consumption of added calories. Indeed, in the past, a popular bodybuilding nutrition technique involved what was called "bulking up." This involved eating a lot of food for purposes of gaining weight. With the added bodyweight came increased muscular strength and energy, which allowed you to train both harder and heavier. But back then, the weight gain was more or less indiscriminate. That is, the greatest concern was gaining enough weight to promote added muscle mass through lifting heavier weights. The composition of the weight gain that resulted wasn't of immediate concern. What that meant in practical terms was that if you gained enough weight, some gain of added body fat was inevitable. But it wasn't a great concern because the bulking up period, which lasted anywhere from 4 to 6 months, was followed by a "cutting phase." that featured fewer calories, increased aerobic exercise, and a faster training pace to meet the goal of removing any excess body fat that might have accumulated during the bulking phase. If things worked out right, you would wind up looking muscular and defined, as well as having larger muscles than previously thanks to the bulking phase.
These days, the bulking-up phase seems to have gone out of style. Most competitive bodybuilders appear to just gain a few pounds during the off-season. Their stated reason for this comparatively conservative off-season weight gain is that they don't want to put on excess body fat. That makes sense from a scientific point of view because of the biology of lipocytes or fat cells. While it was previously thought that body fat was added during three points in life, namely in the last trimester of pregnancy; during the first three years of life; and during adolescence, it's now known that new fat cells can be formed once a certain level of body fat is reached. What happens there is that the existing fat cells divide and form new fat cells, a process known as Hyperplasia. As noted in a recent article in Applied Metabolics some people think the same process can occur in muscle fibers, with new fibers being formed from existing fibers. While the evidence to prove that muscle hyperplasia exists is still debatable, the existence of fat cell hyperplasia is not. What does this have to do with gaining weight for bodybuilders? If you get fat enough during the off-season, there is a good chance that you can develop new fat cells through the hyperplasia process. The problem with that is that while you can reduce the size of fat cells through diet and exercise . . .