Can you provide me with a basic understanding of carbs, fats, and proteins?

– Mandeep P.


Carbohydrate, fat, and protein are the three macronutrients (needed in large quantities) that give us energy. Alcohol also provides calories but is not a nutrient. Water is the other macronutrient but is calorie-free.

Carbohydrates are compounds that are predominantly used for energy in the body to fuel our brain, nervous system, organs, metabolic processes, and muscles. We get 4 calories per gram from carbohydrate molecules that reach our cells. Some carbohydrates aren’t even digested or absorbed – namely dietary fiber. It is specifically identified on a food’s Nutrition Facts panel, as are sugars. Carbohydrates can be simple or complex in structure. Simple carbohydrates are single or double sugar units, while complex carbohydrates are starchy. Sugars are naturally found in fruits, milk and yogurt, some vegetables, but can be added to just about any packaged or processed food. Starches include foods like potatoes, pasta, bread, rice, corn and cereal grains.

Fats that we eat are triglyceride compounds, the same type we store in our bodies. We get 9 calories per gram of fat, making fat the most energy-rich macronutrient. In addition to long-term energy, we use fat for insulation and protecting our internal organs. Each triglyceride has 3 fatty acid strands. Some of the bonds in a fatty acid are doubled-up making them unsaturated. Mono-(single) and poly-(multiple) unsaturated fats are healthier for us than saturated fat. Trans fat is produced unintentionally when in food processing, and unsaturated fat (typically plant oil) is hydrogenated to become solid. These are the worst fats that negatively impact health, even more so than saturated fat. The highest sources of beneficial unsaturated fats are fatty fish and plant foods like nuts, olives, and avocados.

Proteins are chains of nitrogen-containing amino acids that we break down and reuse to form our own protein in cell membranes, antibodies, and enzymes. These are functions neither fats nor carbohydrates can perform, and we don’t have amino acid reserves, so it’s important to get enough protein. We get 4 calories per gram of protein. Some of the amino acids we can’t form ourselves and so are considered essential to our bodies. Protein sources with the most essential amino acids include eggs, poultry, beef, pork, and dairy products. With an adequate amount of a wide variety of legumes, vegetables, whole grains, nuts and seeds, vegans can get enough essential amino acids from plant foods alone.

Did you know?… If you eat too many calories from any energy source, your body can convert it to stored fat.

– Debbie J., MS, RD

This article should not replace any exercise program or restrictions, any dietary supplements or restrictions, or any other medical recommendations from your primary care physician. Before starting any exercise program or diet, make sure it is approved by your doctor.

Some questions have been edited for length and/or clarity.

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