How many calories should you eat for weight loss? The 1200 calorie rule and why it's meant to be broken. Picture of grocery bag full of food spilled over

Best Calories for Weight Loss?

adaptation calorie deficit calorie intake dieting evidence based fat loss how to diet weight loss May 12, 2023

“The secret to losing weight is to eat 1,200 calories a day.”

Hang around the dieting world for a day, and you’ll see this magic number of calories you should eat for weight loss. 

But, if you hang around the science-based fitness world for a day, you’ll see that this number is frequently listed as the “what not to do” dieting advice. 

So why do so many people think that eating 1,200 calories a day is the best way to lose weight, “get a summer body,” or otherwise achieve our fitness goals?


Determining Calories for Weight Loss


What if I told you that this calorie rule started in the early 1900s?

In 1918, Dr. Lulu Hunt Peters first popularized the idea of calorie counting and seeing food as not just food but a number of calories. 

In her best-selling book, Diet & Health: With Key to the Calories, she first assumed that all women seek to lose weight, and to do so, all they must do is stick to a 1,200-calorie diet. 

Better yet, she placed a moral purpose behind this. She argued that eating so little supported the food rationing efforts around the time of WWI. 

In other words, eating 1,200 calories a day was patriotic. (what?? I know.)

Are you catching this?

Society is still hung up on a dieting strategy that was taught over 100 years ago!

This so-called key to weight loss was developed before we understood the nature of human metabolism (a somewhat important piece of the puzzle).

Now, she didn’t get it all wrong. In her book, Dr. Lulu Hunt Peters described the human body as “fireless ovens” (a hint at metabolism) and explained how exercise played a role in the calories in vs. calories out game. 

But she definitely missed some crucial components of fat loss and overall health. Though, in her defense, none of this was discovered yet. 


How Many Calories Do You Need?


We’ve learned a lot in the last 100+ years about dieting, weight loss, fat loss, and our overall health. Possibly the biggest lesson we’ve learned is that caloric needs vary from person to person. 

So if you have a fat loss goal, you will have to figure out what your caloric needs are, and then you can create a calorie deficit from there. 


Basal Metabolic Rate (BMR)

The first step to determining how many calories you need to eat daily, regardless of your fitness goals, is figuring out your basal metabolic rate, also known as BMR. 

Your BMR is the number of calories your body uses to maintain vital processes, such as breathing, heart rate, and brain function. 

Your BMR does not include any additional movement or intentional exercise.

As a 5’7”, 145-pound, 30-year-old, my BMR is around 1,450 calories, meaning 1,200 calories is less than what my body needs to function optimally. 

Your BMR will look entirely different. 


Calculate Your BMR

The calculation for BMR is slightly different for women and men. 


If you’re a woman, you can determine your BMR using this formula:

655 + (9.6 x weight in kg) + (1.8 x height in cm) - (4.7 x age in years)


If you’re a man, you can determine your BMR using this formula:

66 + (13.7 x weight in kg) + (5 x height in cm) - (6.8 x age in years)


Keep in mind that things like daily activity, exercise, digestion, body composition, sleep, stress, food composition, and water intake all play a role in your daily calorie expenditure, which is not reflected in this number!


How Your Metabolism Plays a Role


We’ve learned a lot since the days of Dr. Lulu Hunt Peters. 

One of the most important things to understand about how many calories you need is something called adaptive thermogenesis. This is just a fancy way to say your body is very smart and your metabolism adapts to what you give it. 

It doesn’t matter if you could lose weight on 2,000 calories a day. If you consistently consume 1,200 calories a day, your body will adapt to lower calories through adaptive thermogenesis. 

You won’t notice it, but your body will divert energy away from “less necessary” things like fidgeting, blinking, reduction in body temperature, and slowed cognitive functioning. 

This adaptation is your body’s way of focusing on keeping you alive and is exactly why you eventually plateau after lowering your calories during a diet. 

You will, to some degree, have to keep lowering your calories or increasing your calorie expenditure while you’re dieting. Please seek a professional to help you do this in order to get the most effective (and safest!) results.

It’s also why immediately jumping to 1,200 calories isn’t the move you want to make for successful and sustainable fat loss


How Psychology Affects Your Calorie Goals


If you find yourself constantly self-sabotaging and battling with issues of self-control, the issue might not be you. The thing that’s holding you back from achieving your fat loss goals is your restrictive diet. 

Adhering to a 1,200-calorie diet is not easy from a psychological perspective. 

Previous research provides evidence that the more restrictive you are, the more likely you are to fail. 

When you follow a restrictive diet, you may feel deprived of certain foods that you enjoy or that you’re used to eating. This can lead to feelings of frustration and boredom with your new restrictive diet and then feeling guilty when you deviate from the plan.

Following a restrictive diet can also cause you to develop an all-or-nothing mindset. This means that if you slip up or deviate from the plan, you may feel like you've "ruined" the entire day or week, leading you to completely abandon your fat loss goals.


How to Achieve Your Fitness Goals


What we’ve learned since the days of Dr. Lulu Hunt Peters is that health, fitness, and fat loss are all individualized processes. 

Yes, there are some rules that generally apply (such as you need a calorie deficit to achieve fat loss), but there are also exceptions to rules based on individual circumstances, such as hormonal activity and other factors. 

If you have a fat loss goal, you can start by first checking if you’re ready to diet based on your current health and lifestyle. 

If you are ready to diet, the next steps would be to set some starting calorie goals–and better yet, set macronutrient targets (e.g., protein, carbs, and fats).

At KJO Coaching, we love tracking macros to monitor adherence to a calorie deficit. We’ve even created a free macro tracking quickstart guide that can teach you the basics of tracking macros and how to use macros to reach your fitness goals

Access the free guide here!

Throughout your fat loss journey, you’ll also want to ensure you’re embracing a growth mindset, paying attention to your biofeedback, managing stress, and moving your body sufficiently so you can continue to see progress. 

If that sounds like a lot to handle, we can help!

We specialize in helping busy, high-achieving women like you prioritize themselves and achieve their fitness goals without restriction. 

Our team of coaches will help you optimize your health inside and out so you can achieve and maintain your fitness goals for life. 

Click here to learn more about how we can help you reach your fitness goals!

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Hi, I'm Kasey!

I coach, mentor, write, and teach with one main focus: Build strong bodies and healthy lifestyles, starting with your mindset.


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