Why We Need Carbohydrates, Fat, & Protein In Our Diet

Why Our Bodies Need Carbs, Fat, & ProteinWhy Our Bodies Need Carbs, Fat, & Protein

The cover of TIME magazine on March 26, 1984 entitled CHOLESTEROL And Now The Bad News…. and Dr. Robert Atkins’ book Dr. Atkins New Diet Revolution published in the 1990s are two symbols of the low fat and low carbohydrate crazes that hit the United States during that time. The theories that lowering your fat and/or carbs can help one lose weight and reduce chronic disease, especially heart disease, spawned cookbooks, diets, and foods that are still seen in bookstores and grocery stores around the country. This is even after TIME magazine came out with a cover in 1999 entitled CHOLESTEROL…And Now the Good News stating that the science was wrong about fat. In all of this hoopla, what got lost was that our cells and bodies need some fat and carbohydrates to function well. We just need to make sure that we eat healthy versions of them and in moderation. So I thought I would discuss why our body needs carbohydrates and fat, alongside why we also need protein in our diet.

Glucose, a monosaccharide is the major source of energy for both plants and animals. Plants produce glucose during photosynthesis and store it as either cellulose or starch. We cannot digest or use the energy from cellulose, but cellulose is nevertheless essential in our diet because it exercises our digestive tract, keeping it clean and healthy. The glucose our bodies use as energy comes mostly from starchy plants, including potatoes, rice, and wheat. The starch in these plants is broken down by enzymes called amylases that are present in our saliva and digestive tract. Our cells then convert the glucose into ATP through a process called cellular respiration, and the ATP is used directly by our bodies to fuel its activities. (As an analogy, think of crude oil that is extracted from the earth through oil wells as glucose and the gasoline that is pumped into our cars, generated from the crude oil, as ATP.) The glucose our bodies do not use is stored as glycogen in muscle and the liver to be converted to ATP when needed; and when present in great excess, our bodies convert glucose into the storage form fat with the help of insulin. This is why it is important to avoid eating tons of carbs and, if we do, to eat whole grains and healthy carbs like brown rice and fruit that have fiber. These foods take longer to digest and do not result in high blood sugar levels to stimulate their conversion to fat. Beyond its role as an energy source, our cells also link glucose to proteins that are involved with the adhesion of cells to each other. Think leaky gut.

Good sources of carbohydrates: Quinoa, barley, bulgur wheat, sweet potatoes, legumes, fruit, oats, and popcorn.

In the beginning of time when we did not have vending machines and convenience stores at every corner, fat helped keep us alive during the cold, lean winter months. Although some think fat is not necessary anymore because food is available throughout the year, fat still does a lot of good. In addition to providing energy and insulating us in times of low consumption and cold weather, fat, also called lipids, make up the membranes that surround our cells, protect our internal organs from physical harm, and they are used to make many steroids and hormones that are essential to our biology. When eating fat, the preference should be to eat unsaturated fats like olive oil. However, that does not mean we cannot eat butter, which is a saturated fat, once in awhile…everything in moderation.

Good sources of fats: Avocado, almonds, walnuts, peanut butter, canola oil, olive oil, olives, salmon, and flaxseeds.

Cells make up tissues, which make up organs, which make up our body. There are about 200 different types of cells and in total there are approximately 37 trillion cells in the human body. It is important that cells know what they are doing so they, and therefore we, stay healthy. DNA holds all of the information of the cell and that information is converted into protein, which actually gets the work done. One of the ways I describe it to my students when I teach Cell Biology is that DNA is the foreman who stays in his office managing the plant and proteins are the workers making the product. Protein controls how our cells communicate with each other, how they stay attached to each other, and via antibodies how we defend ourselves in times of infection. Our protein hemoglobin stores and carries oxygen through our blood and enzymes are proteins that make reactions happen. Additionally, we can thank the structure of our hair, nails, muscle, skin, cartilage, and ligaments to protein. Proteins are made up of chains of amino acids and some are non-essential (meaning our body produces them) and others are essential (meaning we need to obtain them from our diet because our body cannot produce them), which is why it is important to eat protein. However, although we need to eat protein, as Americans we tend to eat more protein than we need (average steak served in a restaurant is 8 oz when we should be eating no more than 3 or 4 oz.).

Good sources of protein: Nuts, peanut butter, grains like quinoa and millet, chicken, turkey, meat, fish, eggs, tofu, beans, lentils, seeds, and dairy.

So next time you walk by a low fat or low carb item in the food store, ask yourself if it is a healthy choice and whether a better option would be to eat real food. Especially when you consider the sugar and chemicals added to make these products “tasty” to eat.

First Photo from TIME Magazine, March 26, 1984. Cover Credit: Andrew Unangst
Second Photo from TIME Magazine, September 6, 1999. Cover Credit: Andrew Unangst



  1. Really informative post! I’ve seen a lot of research out there about how important it is to get enough carbs, and as someone who’s struggled with disordered eating in the past, I’m a big believer in advocating for a balanced diet with plenty of all three macronutrients.


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