I'm with Crankin. 
Your brother can't count on a change, though it may help to change his diet there are no guarantees.  I eat a relatively low fat diet with very little meat.  High fat, low fat, high carb, low carb,  it doesn't seem to effect my cholesterol levels much at all.  I still have to take the drugs.  Even when I went ultra low fat my cholesterol levels didn't drop enough to drop the meds.  
My BP is high.  Exercise made no difference at all.  I eat a low salt diet.  It is a big enough problem that I think I am going to have to change my BP meds as the old ones are not working quite as well as they once did.  And this is exercising more than I have ever exercised in my life and this is being thinner than I have been since 1980.  My sister is a hair taller than I am and weighs almost twice what I weigh.  Her BP is low.
				
			 
			
		 
			
				
			
			
				Trek Madone 4.7 WSD
Cannondale Quick4
1969 Schwinn Collegiate, original owner
Terry Classic
 Richard Feynman: “The first principle is that you must not fool yourself and you are the easiest person to fool.”