Can you gain body fat on 5000 calories a day for 21 days?

Stupid question?  People gain weight all the time on seven-day cruises, where news articles have told us that the typical weight gain for passengers on a seven day trip is 1 lb per day.  But what if the macro ingredients of those calories were low carb high fat (LCHF-10% carbohydrates, 50% fat and 40% protein).  Sam Feltham did this last Spring.  He gained about 1 kg but lost 3 cm from his waist.

Fat in the absence of carbohydrate is not the devil.  The devil is in the carbs.

The Battle of the Diets: Stanford Professor reports that the result of his research on diets was a bitter pill

Standford nutritionist and vegetarian, Christopher Gardner, says that his research showing low carb diets as the most effective for losing weight and controlling lipid markers says that it was a bitter pill to swallow.