The three major food groups are protein, carbohydrates, and fat. Fat may be the most misunderstood of our bodies’ trio of basic nutrients. Like protein and carbohydrates, it is made up of carbon, hydrogen, and oxygen, but in different proportions. These proportions make it easier to store. When fats are broken down in the body, they are joined with cholesterol and proteins to make new molecules called lipoproteins. Lipoproteins come in two principal types: high-density and low-density. Low-density lipoproteins, made of cholesterol, cholesteryl esters, phospholipids, triglycerides and protein, are known as the “bad” lipoproteins as they tend to form plaque deposits on the blood vessel walls.
Cholesterol, a distinct chemical structure, is not evil and is vital to a healthy life. Most cholesterol is locked up in the body’s cells doing its’ job while only about 7% floats in the blood stream. The healthy approach to cholesterol is to maintain it at a healthy level. One way to do this is to eat a lot of fiber from plants. Fiber contains no calories or vitamins but helps to lower cholesterol by slowing the rate sugar gets into the blood stream to be turned into fat.
The human body likes to hold onto fat, so it has a source of energy when it runs out of carbohydrates. Fat supplies energy and assists the body in absorbing the fat-soluble vitamins, A,D,E,and K. Fat is stored beneath the skin or around the belly. Fat is only stored if more fat is taken in than your body needs for energy. Fat (9 calories/gram) contributes more than twice as much energy as protein and carbohydrates (4 calories/gram).
Fat comes in several varieties. ‘Saturated” is a description of the chemistry of the bonds of carbon and hydrogen. Dietary fat contains varying proportions of three types: monounsaturated fat, polyunsaturated fat and saturated fat. Monounsaturated fat is the healthiest kind and is found in olives/olive oil, walnuts/walnut oil, peanuts/peanut butter and oil, cashews and canola oil. Polyunsaturated fat is found in corn, safflower, sunflower, soybean, and cotton seed oils. Saturated fats are mainly animal fats while vegetable fats tend to be unsaturated, but there are many exceptions.
Fats should make up less than 30% of the calories in your child’s diet with a third or less of those calories coming from saturated fats (10% or less).
Research shows that some sources of saturated fats don’t necessarily up the risk for heart disease. Sources such as whole-fat dairy, dark chocolate and unprocessed meats. The body needs unsaturated fats, both monounsaturated and polyunsaturated. While unsaturated fats are essential, you should not take too much of a good thing.
Many of the diets adults use to try to lose weight are low fat diets (under 20%). It has been found that they can be unhealthy. Children under 2 years should not be on low fat diets and after two years the focus should be on replacing unhealthy fats with healthy fats in the correct amount.
By Sally Robinson, MD
Keeping Kids Healthy
University of Texas Medical Branch (UTMB)
Published January 2026