Cooking Meat: Muscle vs. Fat

Most people I know don’t buy cuts of meat they’re not familiar with because they have no idea how to cook it, so they stick with chicken breasts and ground beef because it’s all they know.

A few weeks ago I was on a late-night run to the grocery store with a roommate and I spontaneously decided to get a Boston butt roast. She looked at me like I was crazy and even said, “You are SO weird.” Over the next few months I’ll be breaking down some basics in cooking meat. My goal is to give you enough information to look at a “weird” cut of meat and be able to use your intuition and basic rules of thumb to cook your way around a question mark.

One simple rule of thumb when you’re decided what to do with a cut of meat is to consider the fat content of the cut. Lean cuts of meat have a low fat & collagen content, like chicken breast or a beef tenderloin. Cuts like a Boston butt roast, ribs, chicken thighs, or a pork shoulder have much more fat throughout.

Determining whether or not your meat is fatty or not, fortunately for us, is easy, as we can see the fat with the naked eye. You can look at a filet mignon and notice that there is not fat marbled throughout, rather than a Boston butt which totally marbled with fat.

You will often find that fatty cuts of meat are generally cheaper, while lean cuts of meat are generally more expensive.

An oversimplified rule of thumb:

Fatty: Low and Slow

Lean: Quick and Hot

There are exceptions to this rule, but I don’t believe you’ll have to worry about the majority of these exceptions on a daily basis. Just because it’s lean doesn’t mean you always have to cook it quickly. For example, shark steak is very tough and needs more than a quick sear.

Consider the shark: He’s one giant muscle! He’s fast and furious and constantly swimming, often times for very long distances. Those muscles are hard and tough and need a little longer to break down the fibers.

Now consider the cow: It pretty much stands all of its life and takes a stroll in a field on a good day. Some of its muscles which are needed to stand may be quite tough and fatty, or else it couldn’t hold up its massive body. But the filet mignon, for example, is located deep within the cow and although it is a muscle, it is not a weight bearing muscle. It is low in connective tissue and very tender. It’s dainty and puny, and doesn’t need much to cook it.

Basic food fact:

When fat is heated long or hot enough, it melts, or renders.

How much it melts depends on how much fat is on the cut, but when it melts, it lubricates the muscle fibers which keeps it moist. So a perfect steak will have just enough fat to melt in the grilling process to keep the muscles moist–rather than a cheap cut with no fat, which will be tough and dry.

Consider a beautiful salmon steak. 

You can see the thin rows of fat marbling throughout the fish. But because there are no high concentrations of fat in any particular area the fat easily renders under heat, causing the final product to be extraordinarily moist.

Most fish have muscle fibers that are also very short, unlike beef. The fibers aren’t held together by collagen which can be tough to cook down, rather, their connective tissue is myocammata and it breaks down much more easily.

Slow Twitch vs. Fast Twitch Muscles

Slow Twitch: Low and Slow

  • Dark meats (ex. Chicken thighs, ducks, geese, flank steak)
  • Slow and steady movement
  • Endurance muscles & ligaments (for flying and swimming)
  • More fat for more energy for the live animal
  • More fat and moisture when cooking
  • More flavor

Fast Twitch: Quick and Hot

  • Muscles for bursts of energy (ex. Chicken breast, small white fish)
  • Less moisture/fat (dries out easily when cooking)
  • Less flavorful

Some of you have probably put chicken breasts in a slow cooker and let it cook all day. Have you ever noticed that most of the time, slow cooked chicken breasts in liquid can often times taste dry? It’s because there is no fat in a chicken breast–there is nothing to render.

So how do I cook chicken breasts?

Quick and hot! If I’m cooking for myself especially where presentation is not key, I almost always cut the chicken into chunks. I then heat up a screaming hot nonstick pan and add a little oil or butter. When the oil is hot, hot, hot, drop the chicken in. Learn how to flip your food in a nonstick pan, because this is a perfect opportunity to use that skill. By flipping the chicken pieces in the pan, you can cook it quicker, easier and more even. Depending on the size of the pieces and the heat of the pan, this should not take more than 4-7 minutes.

How do I cook a big, fatty beef or pork roast?

Low and slow! You’ve got to give that fat time and heat to render (melt). I prefer to sear the roast on very high heat in a pan on the stove. Then, transfer it to a slow cooker with stock (and usually onions, garlic and salt), put the lid on and let it cook all day. Like you can see in my short ribs, those fatty cuts need time to break down.

About Ande Truman

Ande has made mistakes in the kitchen since she could reach the countertop. From a restaurant head cook, to cooking meals for friends, to her own solo plate, experimenting & learning drives her. She's also a freelance graphic & web designer, photo/videographer, guitar player and wanderlust-er. In her spare time, she works a full-time 8 to 5 cubicle job. She's the creator of Broke & Healthy.

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  1. […] *Side note: Why did I go with a fatty cut like a Boston Butt? Because roasts need fat if they’re going to cook all day. That fat is going to render down and moisturize the muscle around it. That’s what helps it fall apart after hours of cooking. More info about cooking muscle vs. fat.  […]