So, the most likely cause? A cascade of failures. Obesity stressed his heart and organs. Diabetes damaged his blood vessels and immune system, making that leg infection worse. The infection got into his bloodstream (sepsis). And on top of all that, he probably had morbid obesity-related heart failure. His mechanics just gave out.
The official record from 1547 just says he “departed this life.” Very polite. Very Tudor. But the true story is a traffic jam of bad decisions and stubbornness. He was fifty-five years old, which is honestly not that old. You probably know people in their fifties who run marathons.
Next time you’re tempted to skip a walk just to finish a bag of chips, remember the king in the jeweled codpiece. He had absolute power, a palace full of chefs, and a personal physician. And he still got his cause of death handed to him by a bad leg and a binge-eating habit. If it can happen to a Tudor king, it can happen to any of us. So maybe go drink a glass of water. Henry would definitely not approve.