A trend that's been picking up some steam in the fitness marketing industry is the theory of three different body types: the mesomorph, ectomorph, and endomorph. As the story goes, we are predisposed to align with one of these body types, which I'll briefly describe:
Mesomorph - The 'ideal' body type, the mesomorph is an athletic build with broad shoulders, a narrow waist, considerable lean mass and low bodyfat. This type of person will be on the covers of fitness magazines.
Ectomorph - A more gangly physique, an ectomorph more closely resembles Shaggy from Scooby Doo. Tall with long limbs, low bodyfat, and not too much muscle. Some may call this type of person 'sinewy'.
Endomorph - Stout is a good word to describe this group. Higher bodyfat with a (possibly) considerable amount of muscle. Endomorphs aren't necessarily short, but the proportion of their bodies can depict them as such. Linebackers will often fall into this category.
So, the question is, are we really destined to fall into one of these categories? Further, can our choices allow us to jump from one body type to another? Interestingly, this body type classification is often used when discussing our natural tendancies, and which direction our body would take us if we didn't put it through any intense conditioning. There are certainly a few factors here that we can't control that lend credence to the concept. To name a few, we have:
- Bone structure - Yes, it is indeed possible to be 'big boned', as well as medium boned, and small boned. This is best seen in places such as the wrist and ankle, where body fat is usually minimal and a good marker for bone size. There are a few ideal weight calculators out there that take bone size into consideration
- Height - In the same topic as bone structure, our height would seem like the attribute pertaining most to our body composition. Although I disagree that it is a huge factor, it can still influence our body type. Take a 6'2" person with an arm circumference of 15" and compare it with a 5'8" person with the same arm circumference. Proportionally, the shorter person will seem to have very large arms and could be considered a mesomorph. The tall person's arms will seem considerably smaller and could still fit in to the ectomorph category. For a tall person, the muscle must cover a greater area, so gaining visible mass requires a higher caloric intake than a short person. A number of pro bodybuilders hover around 5'8", since their mass gains are most noticable.
- Muscle Fiber Types - The body is composed of both slow-twitch and fast-twitch muscle fibers. The slow twitch are used for endurance activities, such as running, cycling, and so forth, while the fast-twitch fibers are most used during quick bouts of heavy lifting. We are born with a set amount of fibers and some of us will have a higher ratio of one fiber type to another. Generally, those with more fast-twitch fibers will be more adept at weight lifting, and those with more slow-twitch fibers at endurance activities. While not directly responsible for our body type, our fiber amount and ratio can influence the activities we pursue, so as an example, an ectomorph is more likely to have a high ratio of slow-twitch fibers.
It certainly seems that there's some genetics at play when discussing body types. However, the whole concept of the mesomorph, ectomorph, and endomorph is purely appearance-based. Through a rigorous routine, an ectomorph can appear to be a mesomorph, combining a high-calorie diet and mass-gaining exercise. So is this person no longer an ectomorph? At that point it seems irrelevant since the definitions are quite arbitrary. Overall I'd say not to put too much stock into evaluating your own body type, but knowing your genetic qualities can be useful in setting more realistic goals. Don't feel that your fate is sealed because you seem to fit in one of these categories.