Hypertrophy is triggered by resistance training, but it doesn’t end there. Muscle growth requires proper stimulus, proper nutrition (macro-nutrient and caloric surplus) and rest (sleep, non-training days) to happen.  I think you get the idea: You eat, you sleep, and you train for bodybuilding. Have I ever seen that somewhere?

But bodybuilding isn’t just about building muscle! It’s also about revealing it. As we have learned, growing muscle takes proper nutrition, which involves a caloric surplus. When a person wants to build muscle they need to eat more energy than they spend, hence having leftover to add lean tissue on their frame. However, science has not yet come to a clear consensus on the exact caloric surplus needed to put on lean tissue exclusively. Meaning that ­— as far as we know — with any surplus, eventually comes fat gain. *Gasp* ...Oh, no!  And thus we encounter:  Bulking and cutting. Bulking is performed when one aims to build muscle.

So yes, bulking is a hypertrophy-oriented phase, meaning, muscle gain is prioritized. However, as we have also established, with such comes the inevitable fat gain, or “getting too soft” in bodybuilding lingo. “But bodybuilders are shredded!” you may think. Well, yes, they are, because after they’re done building their muscles they often lose the fat. This is called “cutting” or “prep” for builders in preparation for a bodybuilding show where they need to drop body fat.
Some people see this pattern of dieting and think of “yo-yo dieting”. And although it is a close concept, it doesn’t cover the entire picture.

However, how lean is too lean?

Each sex has different minimum body fat % requirements for correct physiological function. Yet, these are, again, minimums. Aka, the slippery edge that risks long-term health problems. For the past century, the Zeitgeist has glorified "skinnier" bodies. And before I get into anything further, let me make something abundantly clear:

I am not talking about you

I am talking about "averages". If you're skinny and healthy, good for you (and the same for the opposite situation). But research shows that the average human body performs best within these guidelines.

Ok, with that out of the way

"No way body fat has a function, if everyone is telling me I need to get abs, like yersterday!"

As stated by the Nutrition Source:

Body fat regulates essential bodily functions including energy storage, body temperature, and hormone production. It releases hormones like leptin to control appetite and satiety, adiponectin to improve insulin sensitivity, and others that affect metabolism, inflammation, and reproductive health. Body fat also provides insulation and protection for organs.

So yes, there's such a thing as being too lean, because when you get to that point, then all of those functions get compromised.

Each sex has different essential body fat percentages, with males ranging from 5% to 10%, and females from 10% to 14% That's a considerable deviation in terms of lbs of fat, so while someone may feel great at 12%, their neighbor may not.

Bodybuilders are expected to walk along this thinly defined line of leanness, constantly risking their reproductive, and overal physiolgical health for the sake of the sport. There's something to say about this dedication, but also, a question to ask: why are we subjecting these athletes to limits that are unquestionably damaging, especially for females? But this craze doesn't only affect bodybuilders, it affects the general population at large.

Dipping below essential bodyfat is already a concern with bodybuilders, but nobody seems to address the fact that steep caloric restrictions for long periods of time is the primary cause of amenorrhea, and not the body fat percentage. And the general population is more and more drawn to caloric restrictive diets every time.

So before you start to go cutting your calories without really knowing what you're doing, please check out the people on my resources page (especially Lyle) so you don't regret it later.