About 25 years ago I had an adult male (we will call him Jim) start classes. He is 6'5 and at the time weighed north of 400lbs. Over the course of 2-years he shed over 100lbs with no other lifestyle changes. Jim always lived a healthy lifestyle as far as food and consumption and had grown up in an active environment. Had you seen him working or been around him for any length of time before starting classes, you would not have thought of him as overweight, just very big and stocky. And strong.
Fast forward 2-years, Jim is still training and doing great. But Jim was always very stiff and never had a great stretch. Most of his movements look different, but man oh man are they strong and effective. His form and patterns are technically correct, but they look different since, in reality, everything Jim does looks different given his size.
Jim moved slower than average through the Gup belts of his own choice. He is a bit of a perfectionist. If you saw him today, (possessive) you may think he is not proficient, but you could not be farther from the truth.