HOPEFULLY by weight you mean muscle mass. Real muscles are very tight/firm muscles; while bulky muscles can be loaded with fat and water, etc.. If your wanting bulk, then grains supply bulk. If you consume grains, the best way is to choose alkaline type RAW grains and chew them to a liquid along with muscle building exercises.
Yet this fall, I plan on putting the greatest muscle building book ever written on the Pro Sports folder. The author started in his 70's after being near dead and turned around in 2 years and won a muscle building contest and later in his years became extremely strong.
A male 6 foot tall is suggested to be 160#, based on that, you can judge if your on the thin side.