Meat contains millions of coiled and tightly packed protein molecules. The protein is what holds meat together and gives it a firm, springy texture. Protein strands also trap moisture in the meat, with most meat made up of around 75 percent water, note the Exploratorium's Science of Cooking guides. When heated, the protein break apart and contracts. This forces water out of the meat, shrinking the overall size and reducing the weight. This is why your grilled pork chop weighs less than the raw, water-rich version.

Dry cooking methods cause meat to shrink more than "wet" cooking methods. For example, when beef chunks are stewed, the surrounding broth keeps the meat moist. But roasting, barbecuing or smoking meat can trigger faster shrinking unless you replace the juices or take steps to keep meat moist. For example, when roasting a ham joint, expect it to shrink by around 25 percent in weight.

Meats of different types and cuts shrink at different rates. The general rule is that the leaner the cut, the less the meat will shrink. This is because the cut contains less water and fat. According to statistics from the U.S. Department of Agriculture, beef sirloin shrinks by around 16 percent when cooked, while brisket shrinks by around 30 percent. A broiled chicken wing may lose only around 14 percent of its weight, while a whole roast chicken may shrink by almost 40 percent. Cured roast ham may shrink by 8 percent, while a grilled pork patty could lose around 30 percent of its weight.

Even when cooking meat using dry methods, you can reduce the amount of shrinkage. For example, ground beef patties will quickly lose moisture and fat when cooked at high temperatures. A moderate temperature helps them to retain moisture and weight. When barbecuing or roasting, drizzle juices over the meat regularly. Using olive oil or another type of fat on the meat also helps to keep water inside.