How Many Calories Should I Eat to Lose Weight?

Karen Buzby, RD, LDN, member of the Penn Metabolic and Bariatric Surgery team, discusses calorie needs, and how many calories you need to lose weight.

Many people want to know: "How many calories should I eat to lose weight?"

Any discussion of weight loss needs to start with understanding calorie intake and energy expenditure or physical activity. Weight loss is the result of eating fewer calories than your body needs or burns.

To lose weight you need to consistently reduce the number of calories in the food you eat and the beverages you drink.

For example, deceasing calorie intake by 500 calories a day for one week should result in a one pound weight loss, (500 calories/day x 7 days = 3,500 calories/week; 3,500 calories = one pound).

Write or Record It

Start recording what and how much you eat over several days. To determine your calorie intake use an online or smart phone calorie counting application, such as MyFitnessPal.com, LoseIt.com, or the Super Tracker on ChooseMyPlate.gov. Using a book on the calorie content of food or referring to the calories/serving on the nutrition facts label on food products can also provide the information needed to track calories.

Compare What You Eat vs. What You Need

Next, compare the number of calories you are eating to the number of calories your body needs to maintain your current weight. Calorie needs can be estimated using an equation that predicts an individual’s resting energy expenditure (REE). This is the amount of energy needed to maintain our basic body functions such as heartbeat, breathing, muscle tone, body temperature, and nerve function. Factors that influence REE are age, gender, height and weight.

The online applications mentioned above will calculate your energy requirements. To do it yourself - get your calculator out!

To determine your REE, you need to calculate your weight in kilograms (kg).

To determine your weight in kilograms, divide your weight in pounds by 2.2.

Then determine your height in centimeters (cm) by multiplying  your height in inches by 2.54.

The most commonly used prediction equation is the Mifflin – St. Jeor. (1)

For Men, REE = [ 10 x weight in kg] +[6.25 x height in cm] – [5 x age in years] + 5

For Women, REE = [10 x weight in kg]+ [6.25 x height in cm] – [5 x age in years ] - 161

Usually the REE is multiplied by an activity factor to estimate your total energy expenditure.

• If you are sedentary or have low activity (walking less than 2.2 miles/day) use the calculated REE for your calorie goal. 
• If you are active (walking about 7 miles a day) multiply the REE by a factor of 1.3.

To figure out your daily calorie goal for a weight loss of 1 pound per week, subtract 500 calories from your REE.

Find Other Ways To Decrease Calorie Intake

Increasing daily activities (for example taking the stairs instead of an elevator, raking leaves, pushing a stroller) or starting an exercise program (dedicating 30 to 60 minutes a day 5 days a week to moderately intense activity), will help burn more calories and help prevent weight gain. Limiting calorie intake and increasing activity is a winning combination for anyone who wants to lose weight and keep it off.

Lose Weight at Penn Medicine

Penn can help you lose weight.

Learn about medical weight loss in Philadelphia, and the Penn Bariatric and Metabolic Surgery Program at a free information session about weight-loss surgery in Philadelphia.

There, you will hear about your weight-loss surgery options, and how Penn can help you lose weight and get healthy for good.

Register for a free information session today.

1. Mifflin, MD, St Jeor, ST, Hill, LA et al. A new predictive equation for resting energy expenditure in healthy individuals. AmJ Clin Nutr 51: 241-247, 1990.