Revealing mistake: In Episode 2 during the scene when the king's son is born, it appears that the baby has been born for less than a few minutes, but when he is held up it is plain to see that his navel has healed instead of being freshly cut As It Should Be after the birth. (00:31:50)
Continuity mistake: When Buckingham is about to be arrested, the camera is looking directly at him. At this angle, his black fur collar is flipped up, covering the neck of his white shirt. When the scene changes to a wide shot behind him, the collar is folded down. (00:35:00 - 00:35:50)
Revealing mistake: The king arrives to see his first son. As the king gets off his horse and is greeted by a foot solider, you can see modern grey fencing behind him with green shrubbery growing around it.
Deliberate mistake: Around the 26 minute mark, when Charles Brandon joins Margaret for a game of cards during their voyage to Portugal, Margaret has a glass of wine (and later Brandon) in which the liquid is not sloshing around As It Should Be on a ship that is rocking and swaying the way it should. (00:26:10)
Revealing mistake: In the scene where the King's sister is throwing things at Charles in rage, she says "don't call me wife" and hurls a goblet at him and it hits the window behind him. A sound of breaking glass is heard, yet you can see the plastic 'window' flap and the 'glass' stays in tact. (00:38:50)
Revealing mistake: In the scene where the king and his entourage are walking through the crowd, someone in the crowd (right side) is wearing a watch on his left hand while applauding.
Answer: While he was obese for much of his life, Henry VIII didn't gain significant weight until after the death of Jane Seymour when he fell into a deep depression and succumbed to the pain of a leg injury he obtained from a jousting accident. He should've been heavier but he wasn't obese for his whole life, especially during his younger years. He was known to be 210 pounds, standing at 6'2", and to have a 32" inch waist for much of his life.