Understanding Calories – How Many Calories Should I Eat to Lose Weight?

Why is it so difficult to lose weight? That’s a question asked by millions of people around the world every day. It can seem like a riddle – especially when you consider how many different diets and workout plans there are…

And a big part of the mystery involves calories – the units of heat that measure how much energy we use to burn the food we eat.

Some diets insist on calorie counting and other focus more on macros – how many grams of carbohydrate you’re eating, for example. Calorie consumption and burning is a topic that’s been around for a long time and yet still doesn’t get the attention it deserves.

So, let’s talk about it. How many calories should you eat to lose weight – and how do you figure it out?

How many calories do I need to burn in a day to lose weight?

What Is A Calorie?

A calorie is a unit of heat. While we tend to associate them with foods and beverages, the truth is that anything that contains heat has calories.

To make matters a bit confusing, there are two types of calories. They are:

  1. A small calorie (cal), which is the amount of energy needed to raise the temperature of one gram of water by one degree Celsius; and
  2. A large calorie (kcal), which is the amount of energy needed to raise the temperature of one kilogram of water by one degree Celsius.

Large calories are sometimes referred to as kilocalories because they contain 1,000 small calories. However, the calorie counts on the sides of food packages are kilocalories.

Confusing, right? It means that your 100-calorie snack pack has 100 kilocalories and 100,000 calories!

For the purposes of this article, we’ll use the word “calorie” to refer to large calories. That’s the way most of us think of them, anyway.

How Many Calories Do We Need?

The key to figuring out how many calories you need to lose weight is understanding, first, how many calories you need to maintain your weight. There are two calculations to do to help you determine what your body needs.

Basal Metabolic Rate

The first calculation you must complete is your basal metabolic rate, or BMR. Your BMR is the number of calories your body needs to function. The word “basal” means base, so when we talk about functioning we mean the bare minimum required to keep your heart beating and your blood flowing and your bodily functions working.

How to calculate Basal Metabolic Rate

The calculation for BMR is not a complicated one. Here’s how to calculate your BMR. (It’s different for men and women, so choose accordingly.) To do the calculation, you’ll need to know:

  • What is your current weight in pounds
  • Your height in inches
  • How old you are in years

If you’re a man, this is the formula:

66 + (6.23 x weight in pounds) + (12.7 x height in inches) – (6.8 x age in years)

That means that for a 180-pound man who is six feet tall and 50 years old, the BMR would be:

66 + (6.23 x 180) + (12.7 x 72) – 6.8 x 50) OR: 66 + 1,121.4 + 914.4 – 340 = 1,761.80

For women, the formula is:

655 + (4.35 x weight in pounds) + (4.7 x height in inches) – (4.7 x age in years)

If you’re a 140-pound woman who is 5’5” tall and 35 years old, the BMR would be:

655 + (4.35 x 140) + (4.7 x 65) – (4.7 x 35) OR: 655 + 609 + 305.5 – 164.50 = 1,405

Once you have calculated your basal metabolic rate, you can move on to the next step.

Total Daily Energy Expenditure

Your basal metabolic rate only takes into consideration the energy, in calories, required to keep your body functioning and keep you alive. It doesn’t take into consideration your activity level – and that’s something that makes a big difference when you’re trying to determine how many calories to eat to lose weight.

That brings us to your Total Daily Energy Expenditure or TDEE. The TDEE starts with the BMR and multiples it by a factor determined by your activity level.

How can I reduce my stomach fat?

The TDEE uses something known as the Katch-McArdle multiplier to estimate the thermal effects of exercise. To begin, choose your activity level from the following options:

  • Sedentary – little to no exercise + a desk job = 1.2
  • Lightly active – light exercise one to three days/week) = 1.375
  • Moderately active – moderate exercise three to five days/week = 1.55
  • Very active – heavy exercise six to seven days/week = 1.725
  • Extremely active (very heavy exercise, hard labor job and/or training 2x/day = 1.9

Now, let’s use the BMRs we calculated before to arrive at the TDEE for our two examples.

  • If the 50-year-old man gets moderate exercise by visiting the gym three days per week, his TDEE would be (1761.80 x 1.55) or 2,730.79
  • If the 35-year old woman is an exercise buff and very active, her TDEE would be (1.405 x 1.725) or 2,423.63

As you can see, her high activity level puts their TDEEs closer to each other than they would be if they had the same level of activity. For comparison, if they both had moderate activity, his TDEE would stay the same and hers would drop to 2,177.75.

Your TDEE tells you how many calories you burn per day, on average. In other words, it’s the number of calories you would need to maintain your current weight at your current activity level. If your activity level dropped or you gained or lost weight, you would need to recalculate both your BMR and your TDEE.

How Many Calories to Lose Weight?

Once you have your TDEE calculated, you can use it to figure out how many calories to eat a day to lose weight.

The only way to lose weight is to create a calorie deficit. A deficit is a difference between your TDEE and the number of calories you take in – or, to put it another way, the difference between the calories you take in and the number of calories you burn.

When you take in fewer calories than you burn,  you have a calorie deficit. When you take in more, you have a calorie surplus.

To lose one pound of body weight, you must take in 3,500 fewer calories than you burn.

how many calories to lose a pound a day

Most experts recommend losing no more than two pounds a week. If you wanted to lose one pound a week, you would need to create a 500-calorie deficit each day. For a two-pound-a-week loss, you’d need a 1,000-calorie daily deficit.

Our 35-year-old woman has a TDEE of 2,423.63. She would need to take in:

  • 1,923.63 calories per day to lose one pound a week
  • 1,423.63 calories per day to lose two pounds a week

All in all, it’s a simple calculation. However, there are some other factors to be aware of.

Non-Caloric Factors in Weight Loss

If you’ve struggled to lose weight, you know that sometimes eating the right amount of calories isn’t enough to help you shed those excess pounds. After calculating your TDEE and estimating the number of calories you need to lose weight, keep in mind that other factors may be at play. For example:

  • Food sensitivities and allergies can play a role. For example, some people don’t react well to sugar, which is highly addictive and can be inflammatory. They may need to eliminate added sugar from their diets to lose weight.
  • Hormonal changes can also impact your ability to lose weight. Even though your age is factored into your TDEE, a woman in menopause may need to create a larger calorie deficit to lose weight than a woman who’s still in her reproductive years.
  • Stress can have a big impact on your appetite and your body’s ability to burn calories. In times of extreme stress, your body focuses its energy on the functions needed for “fight or flight” and may slow your metabolism accordingly.
  • Insomnia and sleep deprivation can both slow your weight loss. It’s very important to create and stick to a sleep schedule.
  • There’s evidence to show that using sugar substitutes can lead to weight gain, which is an argument for cutting out diet soda and sticking to water, seltzer, and other unsweetened drinks.
  • Genetic factors may also play a role. Someone who has a genetic predisposition to diabetes, for example, will need to be especially careful with carbohydrate and sugar intake to lose weight.
  • Certain diseases can impact your ability to lose weight. Thyroid conditions, for example, can cause problems at both ends of the spectrum – causing some people to gain weight and others to have difficulty gaining weight.
  • Some prescription medications have been linked to weight gain and/or difficulty losing weight. For example, weight gain is a side effect of many antidepressant medications. Other medications may cause you to retain water or cause bloating.

How do you navigate these factors? We recommend starting with your TDEE and figuring out how large a calorie deficit you want to create.

Then, track your calories and adjust your daily caloric intake and diet as needed. It may take some time to figure out the right calorie count and food combinations for your body, but it will be worth the time you spend when you start to lose weight and regain your health.