How Many Calories Should You Eat To Lose Weight?

A frequently asked question is, “How many calories should I eat a day to lose weight?”. The key principle behind losing weight is to burn more calories than you eat. First of all, let’s see what exactly calories are. Calories are a measure of energy, which our body uses to carry out its functions. Our body gets its energy, which is measured in calories, from the food that we eat. If we eat too few calories, the body would not be able to keep up with its demands. There is the risk of malnutrition, fatigue and deterioration of our body systems. On the other hand, if we consume too many calories, the body is not able to use all of it for energy, and thus just stores it as fat. If you haven’t reached your ideal weight yet and are looking to shed some pounds, you have to learn how many calories you should be consuming. However, in order to figure out how many calories to lose weight, you have to first understand how many calories you need to eat each day to maintain your weight.

The calories that your body requires per day are determined by your basal metabolic rate, or BMR. These are the calories that your body needs to survive and perform its natural processes such as food digestion, excretory processes, protecting you from the heat/cold, etc. These do not yet include other activities such as walking, running, and lifting weights. Active people require more calories than what the BMR dictates. Your BMR plus the calories that your body burns when you carry out your activities equal to your daily calorie needs.

Different formulas have been introduced to calculate the BMR. The most popular formula is known as the Harris-Benedict formula, where age, gender, height and current weight are taken into consideration:

• Women: BMR = (1.8 × height in centimeters) + (9.6 × weight in kilograms) – (4.7 × age in years) + 655
• Men: BMR = (5 × height in centimeters) + (13.7 × weight in kilograms) – (6.8 × age in years) + 66

Conversion:
1 inch = 2.54 cm
1 kilogram = 2.2 lbs

As an example, let’s compute the BMR of a 40 year old woman who is 5’5” (165 cm) tall and weighs 132 pounds (60 kg). The equation would be:

BMR = (1.8 × 165) + (9.6 × 60) – (4.7 × 40) + 655 = 1,340

This means that the woman’s body requires 1,340 calories a day to carry out its functions, for its organs to work properly. That’s too few calories, if you think about it, since the equation still doesn’t include her activity level.

Here are the equations used to calculate a person’s daily calorie needs based on his or her activity level:

• Sedentary people (often seated, with no actual exercise): 1.2 × BMR
• Lightly active people (exercise 1-3 times a week): 1.375 × BMR
• Moderately active people (exercise 4-5 times a week): 1.55 × BMR
• Highly active people (dabble in sports and exercise hard most days): 1.725 × BMR
• Extremely active people (exercise hard every day): 1.9 × BMR

So, let’s see how many calories are needed for the woman to perform her daily tasks. If she is only seated at work and is sedentary on most days, with extra activities that include walking, driving, writing and typing, we multiply her BMR (1,340) by 1.2 (sedentary activity level) and reach the figure 1,608. She needs 1,608 calories per day to keep her current weight. As her activity level changes, we adopt a different equation. Let’s say she starts exercising for 2 to 3 days a week, we then multiply her BMR (1,340) by 1.375 (lightly active) and reach 1,843 calories.

How Many Calories Should You Eat a Day to Lose Weight?

Now that you have the daily calorie needs figured out, how do you know how many calories you should eat per day to lose weight? To lose weight, it is typically recommended to consume about 15 to 20 percent less than your daily calorie needs (read about the best way to lose weight here). Therefore, the woman in our example would need to consume only 1,286 to 1,367 calories per day (sedentary) or 1,474 to 1,567 calories a day (lightly active) if she wants to lose weight.

However, many experts suggest not to eat fewer calories than your BMR. Rather, it is much safer to burn more calories through exercise. As a guide to minimum calorie consumption, the American College of Sports Medicine suggests that the daily calorie intake never drops below 1800 for adult men and 1200 for adult women.

As shown in the figures above, it is much easier to reach your goal of losing weight when you combine diet with exercise, than just through dieting alone (click here to read about exercise for weight loss).

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