In my experience, I have never seen an INTP with what could be called a "large build." A) INTPs have one of the fastest metabolisms of all the types, B) they are thin-boned and, C) they tend to dislike physical exercise, although as Yellow said, they are not necessarily averse to all forms of physical activity as long as there's a cerebral component to it. If you violate any of those three characteristics, and you otherwise don't have a preexisting condition, be it genetic or disease, then 99% probability you are not INTP. It's just not possible. [Human constitutions, like psychological types, tend to occur in discrete clusters. An INTP will never be endomorphic, because then they wouldn't be INTP. The psychological type/body constitution develop together, never separately. If INTPs do gain weight, it will be around the midsection, but even then, it's not going to change the overall thin look.
Sensors are always bound to be more more well-enveloped, whether in muscle or fat. I can tell who is an ISTP in my CS class now simply by looking at which dudes check sports stats on their laptops. Inevitably, all of them have an overall more developed musculature. They actually enjoy sports/exercise, and they're able to actually put on a decent amount of muscle mass if desired. It's tremendously difficult for an INTP to do the same.