When you cook a steak, it will naturally shrink. This is because the muscle fibers in the steak contract as they are heated. The amount that a steak shrinks will depend on its size and thickness. A 6 oz steak will typically shrink by about 25%. So, if you start with a 6 oz steak, you can expect it to weigh about 4.5 oz after cooking. The best way to prevent your steak from shrinking too much is to cook it on low heat. This will give the steak time to slowly cook through without the muscle fibers contracting too much. If you cook your steak on high heat, it will cook faster but will also shrink more. cook your steak on low heat. This will give the steak time to slowly cook through without the muscle fibers contracting too much. If you cook your steak on high heat, it will cook faster but will also shrink more.