Samwise and Mordor

According to my sources: How Long Does It Take to Walk from the Shire to Mordor? | Hiking Middle-Earth

It took about six months and almost 1800 miles to get from the shire to mordor.

Part of the time the hobbits enjoyed relatively good food, but as they journeyed they came to basically only eat lambas bread. Frodo is said to weigh virtually nothing when picked up, by the time they reached Mt doom.

Therefore I ask why in Peter Jackson's movie trilogy is Sam still so heavy by the time they get there? Am I being unreasonable to think hiking 10 miles a day for six months on rations should have had Sam fit and trim?

Well, he was carrying the soil from Galadriel so maybe that caused HIM to grow. But then again, if we're talking movie only - he just had some hair iirc....