Body habitus, or simply habitus, is a medical term for “physique” or “body type.” A wide range of factors can determine body type, and medical professionals often make a note of a patient's habitus on his or her chart as part of a general reference to provide information about the patient's history. Some studies also suggest that certain extremes in physique can be indicators of disease or may lead to certain illnesses.
There are three terms commonly used in reference to body habitus. A patient with an ectomorphic body type is said to be underweight, a patient with a mesomorphic body type is of normal weight, and a patient with an endomorphic body type is overweight. The thresholds of “underweight,” “normal,” and “overweight” have been adjusted on many occasions, and there is some conflict in the medical community about where the dividing lines should fall.
In terms of weight, a number of factors can influence physique. Genetics plays an important role, as do issues such as the balance of neurotransmitters in the brain, a person's level of activity, and their diet. While the news media often suggests that being extremely under or overweight can be dangerous, in-depth scientific research indicates that the situation is actually not this simplistic, and that while weight can play a role in health, weight and health are not directly correlated.
Other terms used in reference to body habitus may describe features such as musculature or strength, along with other characteristics of interest. As a general rule, any change in the physique can be a cause for concern. Many diseases cause patients to gain or lose weight, making changes in body size an indicator that a patient is experiencing a problem; AIDS, for example, is closely associated with emaciation. Patients may also embark on activities which change their body shape, such as when a patient becomes more athletic and develops increased musculature.
Many medications can induce changes in the body, especially if used in the long term. Steroids, for example, are infamous for causing a variety of changes. While these drugs are often associated with attempts to increase strength and musculature, they are also used in the treatment of a wide range of diseases. People who have taken steroids long-term for any reason often develop tell-tale physical signs, such as a distinctive “buffalo hump” on the upper back. Other medications can lead to decreased musculature, weight gain, and changes in the distribution of fat on the body.
Is Body Habitus Genetic?
Genetics can be fascinating, complex and baffling. Sometimes, uncovering genetic causes for certain traits is rather straightforward. On the other hand, it can seem like trying to find a needle in a haystack. While current evidence suggests that genetics contribute to about 80% of your body shape and weight, lifestyle factors can control how those genetics are expressed.
Genetics, Body Shape and Waist Size
Some genetics impact aspects of your body shape. Some people can more easily gain muscle mass because they inherited the trait for it. There's also a genetic component to inheriting an apple-shaped body, probably due to carrying more fat around the midsection. On the flip side, others are genetically predisposed to carry fat in the lower parts of their bodies — hence pear-shaped bodies.
There's more evidence that genes contributing to waist size can also play a role in addictive behaviors, including overeating. Historically, we've not had such ready access as we do now to foods high in calories and carbs but with low nutrient density. That could be one reason why obesity is becoming more widespread.
Genetics' Role in Somatotype
With that said, somatotypes are mostly inherited. In other words, the tendency to be an ecto-, meso- or endomorph comes from your parents' genes. Keep in mind, however, that having a particular body type doesn't automatically make you healthy or unhealthy. Endomorphs, for instance, aren't always obese. They do gain weight more easily, but they also have more muscle mass. Others have a combination of a couple of body types. You could be an endo-ectomorph with more fat around the weight but leaner and thinner in the hips and legs.
What Body Habitus Is Most Common?
There are three somatypes plus combination somatypes. Currently, research suggests that the endo-mesomorph somatotype is among the most common. Some estimates say that about half of the human population has this mixed body type, with a larger rounder upper half and a midsized lower half. As with any mixed somatotype, the endo-mesomorph experiences both the benefits and drawbacks to both base types. Gaining muscle may be easier for this individual. While losing fat is more challenging than for a pure mesomorph, they can still lose it with a little less effort than a pure endomorph.
Other mixed body types include the ecto-mesomorph. This somatotype may have a thinner and leaner upper body with a little more muscle mass in the lower body. Pear-shaped bodies may be more common in this mixed somatotype. Also, they may lose fat more quickly than a pure mesomorph yet gain muscle with less effort than a pure ectomorph.
Pure Somatotypes in the Adult Population
The next most common somatotypes include the endo-, meso- and ectomorph, in that exact order. These are the pure body types described by psychologist W.H. Sheldon during the 1940s. Considering these realities, much of the adult population is either struggling to build muscle or facing challenges while losing weight. None of these are personal failings. The key to doing what is advantageous for your body is understanding how it works when at its best and worst.
Ayurveda and Body Types
It's been argued that Sheldon created this somatotype system from a purely Western standpoint. Ayurvedic medicine, which originated on the Indian subcontinent, also has a body-type system. The vata body type is more slender, while those with kapha body types tend to be rounder and gain weight more easily. The pitta type is described as a medium build and can gain muscle more readily.
Can Body Habitus Change?
People can modify many aspects of their bodies. Weight, muscle mass and tone, dexterity, flexibility, endurance and strength are mostly within our control to develop. However, our basic somatotypes cannot change. An endomorph will always be an endomorph, regardless of how much weight is gained or lost. Ectomorphs remain ectomorphs, so matter how much muscle these individuals build. Similarly, certain aspects of these somatotypes also cannot be altered — bone structure or weight gain tendencies, for instance.
Hormones and Body Type
Sometimes, certain aspects of our metabolisms can change due to medical conditions, medications or other treatments. For example, many transgender men take testosterone to gain male secondary sex characteristics and feel more comfortable in their bodies. This testosterone therapy, even if started during one's middle age or senior years, shifts how body fat is distributed throughout the body. Fat may lessen around the hips and thighs but increase around the midsection. But people on gender-affirming or other hormone therapies cannot alter their basic somatotypes: They still have the same somatotypes they did before starting their therapies.