Macronutrients: How different proteins, carbs and fats work together to fuel your body and energize your brain.

Are you confused about which nutrient to pay attention to when reading nutrition labels? Should you choose low carb? Low-fat? High protein? Here’s a simple primer to help you.

Calories are good for us — yes, really!

While lights run on electricity and cars run mostly on gasoline, realize that the human body also needs fuel to stay alive and to function at our best. We get the fuel we need from food and drinks that contain calories. In fact, calories are simply a measurement of energy or fuel. There are only three nutrients that contain calories (proteins, carbohydrates and fats). These are referred to as “macronutrients” — the subject of this column.

Protein for muscles and more

Protein is concentrated in animal meat, eggs, milk, cheese, yogurt, beans and soybeans. While we often think of protein as a nutrient that helps us build muscle, it does way more. Protein is part of just about every cell in the human body. Antibodies, which fight infection, are proteins. So are the red blood cells that carry oxygen throughout the body and the insulin which regulates our blood glucose. Every day, one to two percent of these proteins break down and need to be replaced by new proteins. How much protein do we need? Because the human body can use only small amounts of protein at a time, it’s best to eat about 20-35g of protein at every meal to meet our nutrition needs. This amount of protein also helps us to feel full. Research indicates that higher amounts of protein at a time will not build more muscle or make us stronger.

Carbohydrates for energy

Carbohydrates are found in fruits and juices, milk products and grains such as wheat, oats and corn. Soda and sweets are also high in carbohydrates. The main function of carbohydrates is to provide fuel for the body — in the form of glucose. While the brain weighs in at just two percent of the body’s total weight, it requires about 500 calories of glucose every day. The nerves, bone marrow and red blood cells, which transport life-giving oxygen throughout our body, burn through another 200 calories of glucose each day. Our muscles use glucose to fuel activity, too. If you don’t eat adequate carbohydrates, the body simply converts the protein you eat (or the muscles in your body) into the required amount of glucose. So, be sure to select a couple of healthier carbs at every meal for efficient energy.

Fat for energy, too

While the brain, red blood cells, nerves and bone marrow require glucose as a fuel, the rest of the body is quite content to burn fat as fuel. In fact, about half of the fuel our body burns to stay alive is fat. Fat is found in so many foods, including meats, eggs, cheese, nuts, olives, ice cream and processed snack foods such as cookies, chips and crackers. Even if we don’t consciously add fat to the foods we eat, we’re probably getting adequate fat to meet our needs.

The good, bad and the ugly

While there are just three calorie-containing nutrients, some of the foods within each group are healthier than others. Healthier protein sources include lean meat, low-fat dairy products, beans and soy. The best carb choices are fresh fruits and vegetables, as well as whole grains such as whole wheat pasta and bread, quinoa and oatmeal. Since hardened fats such as butter can contribute to heart disease, it’s better to choose nuts, avocados, olive and canola oil and tub margarine as your fat options.

Putting it all together

While many people choose to focus on one nutrient, doing so will most likely change the amount of another nutrient. For example, low-carb foods tend to be higher in protein and fat. A low-fat food is often higher in carbs. So, remember that all three macronutrients are essential for life and well-being. At every meal select 20-35g of lean protein, add a couple of servings of a healthier carb, then select a small amount of the best fats.


Dr. Jo Lichten, Ph.D.,
is a nutritionist and registered dietitian living in Florida. As a frequent keynote speaker, she inspires busy people to stay healthy, sane and productive. Jo is the author of several books, including REBOOT – How to Power Up Your Energy, Focus, and Productivity. When she’s not traveling she and her husband enjoy kayaking, biking and surfing.