By Michael Ormsbee, PhD, Florida State University

Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily

Food labels are an effective tool for helping us make healthier eating choices. How do you decipher a label? First, you must decide your total caloric intake, as labels are based on a 2,000 calorie intake. Professor Ormsbee explains.

How Much Food Should I Eat?

When it comes to reading food labels, there is no perfect formula, magic food group, or even a cursed aisle of the supermarket. Instead, there are poor options, better options, and the best options. The first question is often, “How much food should I eat, how many calories?”

The answer depends on who you are, how old you are, how big or small you are, how much muscle you have, what your gender is, and what weight goals you specifically have. These basic indicators will dictate the energy requirements of your body in general. Let’s visit them one by one.

First is age. At different stages in our lives, we have different energy demands—that is, different amounts of calories that we need to live optimally. 

Think of a child who is constantly growing and developing until the onset of puberty. In comparison to their size, a child will likely require more calories than an adult while they are growing so fast. 

During certain events, like pregnancy and breast-feeding, or recovery from injury or disease, we have increased energy demands, requiring a higher number of calories per day. If you become more sedentary as you age, you will require fewer calories. 

If you choose to maintain or increase activity as you age, your calorie intake will stay up. However, be careful here. Older adults often don’t eat enough calories due to a variety of factors, including a loss of appetite. Thus, based on which stage of life you are in, you will likely require varying amounts of calories.

Size and Caloric Needs

Next is body size. A larger person—we’re talking actual body size and not fat mass—is going to require more absolute energy each day than a smaller person, assuming equal activity levels. 

Think of it as a smaller engine versus a larger engine. The small engine just requires less fuel to continue revving compared to the large engine. 

A reasonable example is, again, an adult and a child. The child is growing and requires specific nutritional needs, but in absolute terms the adult needs more calories because they have a greater body area to support metabolically.

The third component to how much food we need is gender. Men tend to be larger than women.  Therefore, based on the previous principle of body size alone, men will often require greater calorie intake than women. 

However, a second factor is the amount of muscle mass that men carry compared to women on average. Though many examples exist where this is not the case, on average, men will have more muscle mass than women. 

Think of muscle mass as hungry tissue. Muscle tissue is highly metabolically active and demands a high-energy intake to keep us moving. With simple math, more muscle mass on your body frame equals more hungry tissue, which equals more food needed.

With these factors in mind, you have an idea of what your basic energy demands are. However, there’s more to the equation. 

Activity Level and Calories

What does your typical day look like? Are you sitting at a desk all day or are you training for a marathon? Or, like most people, are you somewhere in between? 

Your relative activity level determines the amount of food you need to eat every day. If you exercise a lot, you will probably need more food to refuel and recover. However, there are also times when you would not want to replenish your energy stores completely, and the food you require depends on your specific goals.

Are you trying to lose weight? Are you trying to put on five pounds (lb), or 2.25 kilograms (kg), of muscle mass? 

In both of these cases—losing or gaining—total caloric intake will be different, and so will the components of that calorie intake. Another area we cannot ignore is genetics. 

For example, do you have a tendency to gain weight or to lose weight easily? What is the influence of your family history? However, a lousy or a fantastic genetic predisposition must be massaged by the other factors that we can control. 

Overall, your individual characteristics, goals, training status, and even your genetics can influence your daily energy needs. In the research lab, using specialized equipment, and calculations, you can also determine your calorie needs.

On nutrition labels, certain nutrients are based on a 2,000-calorie diet, and by now you know that not everyone eats a 2,000-calorie diet. This number just reflects the average intake of an average-sized person to maintain weight, and serves as the most basic starting point for most people. Thus, determining your actual calorie intake is the first step in reading labels.

This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.

Michael Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University. He received his MS in Exercise Physiology from South Dakota State University and his PhD in Bioenergetics from East Carolina University.