Navigating Your Diet: The Real Impact of a Calorie Deficit on Food Choices

Weight Loss & Diets | Written by Nathan Petitpas | Updated on 16 July 2024

A brunette woman with curly hair eats a slice of pepperoni pizza while wondering if she can eat anything on a calorie deficit or if it only matters that she counts calories.

You might hear that you can eat anything while on a calorie deficit, but it’s important not to accept this claim without skepticism.1 A balanced diet full of healthy fats, protein, and carbs (aka “macronutrients”) is crucial to maintaining healthy hormone levels, body tone, and energy levels while in a calorie deficit.

In other words, it may be possible for a person to eat anything they want while dieting, but it can cause health issues down the line and prove frustrating when the results are subpar.

What Foods Can Be Eaten on a Calorie Deficit?

Technically, anyone can eat any food on a calorie deficit. For example, Mark Haub, a professor of human nutrition from Kansas State University, lost 27 lbs in 10 weeks while eating nothing but Twinkies, Doritos, and Oreos.2

Haub’s experiment “proved” that it is possible to lose weight even while eating junk food. The only thing that mattered was that a person burned more calories than they ate — in other words, be in a calorie deficit.

Stories about this experiment — and the subsequent like that people can eat anything they want on a calorie deficit — spread like wildfire. Haub’s findings are encouraging for those looking to lose weight but find it challenging to stop eating junk food and sugar; it’s easy to see why this is the case.

But while it is possible for people to eat anything they want and lose weight on a calorie deficit, people who fill their daily calories with empty calories (sugary snacks, chips, and sodas) will not be as healthy or see the same type of results as folks who eat healthy, nutrient-rich foods.

Remember, a calorie deficit isn’t about what dieters can eat (if it was, everyone would eat french fries and lose weight) It’s about what dieters should eat to fuel their bodies and stay healthy and strong even as they burn body fat.

What to Eat While on a Calorie Deficit: Can You Really Eat Anything?

Technically, you can eat anything while on a calorie deficit, but it’s more important to consider what you should eat during this time.

Those looking to get fit should focus on eating clean, and this includes taking a look at macronutrients, or “macros,” during a calorie deficit. Macros are the three basic components in food that provide the body with the most energy. They include the following:3

  • Healthy Fats: The body needs both saturated and unsaturated fats to help with hormone production and brain development. People on a calorie deficit can get healthy fats by eating avocados, nuts and nut butter, fish, red meat, and full-fat dairy.
  • Protein: Protein is the building block for muscles — and it is essential to anyone’s diet, whether they’re building muscle or operating at a calorie deficit. Eating protein from foods like legumes, tofu, eggs, white meat poultry, salmon, pork, and plain yogurt can help maintain muscle tone and prevent muscle loss.
  • Carbohydrates: Carbs are the main source of energy for the body and brain. This makes them particularly important in a caloric deficit, as eating carbs can prevent a gym goer from feeling fatigued or low-energy throughout the day. Foods like vegetables (especially green peas, broccoli, corn, and spinach), fruits (like raspberries, apples, and oranges), whole grain bread and pasta, oats, and quinoa are packed with carbs.

Folks who want to lose weight must get enough macros in their diet to experience successful cutting phases because their bodies have everything they need to stay full and energized despite the calorie decrease. These nutrients also have significant benefits for muscle maintenance and overall health and wellness.

Why Can’t You Eat Anything or Whatever on a Calorie Deficit?

We’ve already talked about how people can lose weight by eating whatever they want as long as they maintain a calorie deficit. This challenges the claim that such a fitness strategy is misleading.

It’s a lie because the food people eat has a direct effect on their health. The human body is very complex, with countless processes constantly taking place to keep it running. Macronutrients play a major role in many bodily functions, which is why everyone (but especially fitness enthusiasts) needs them in large quantities. People who try to live at a calorie deficit but fill their diet with unhealthy foods lacking in nutrients are more likely to feel run down and worn out.

An Asian woman in an office and at her desk as she eats fried food with chop sticks and has a milkshake next to her.

Source: RyanKing999 via Canva.com4

Gym goers who don’t get enough protein will have a more difficult time building muscle tone (and if they go too long without protein, they may actually lose the muscle they’ve earned). Those whose diets are too low in fat can suffer from feelings of hunger during the day. And folks who don’t eat enough carbohydrates can experience symptoms like fatigue and constipation.

It’s also important to remember a calorie deficit is only part of the puzzle for successful weight loss. Metabolism is also a significant factor in the calories a person burns — and in many cases, metabolism is not in their control.

In fact, research shows that energy expenditure (the number of calories a body burns) drops by about 15% after a person loses weight.5 If the body is going to metabolize food more slowly, it is even more important to take in foods that actually benefit the body.

Minimum Threshold of Fats & Their Role in The Body

Weight loss beginners sometimes believe that cutting fat is the key to losing weight. After all, they aim to lose fat, so it seems logical to consume less of it.

Not exactly. Fat is actually a very important nutrient for the human body. It is an excellent source of energy. It helps the body absorb vitamins A, D, E, and K. Essential fatty acids even play a role in skin health, and a severe lack of fat can result in dry and itchy skin.6

But perhaps the most important element of fat is the way it affects brain development. Research from Acta Neurologica Taiwanica reports that the human brain is over 60% fat, and a diet rich in healthy fats (specifically omega-3 fatty acids) is essential for proper brain development and function.

Another study, published in Neurology, backs up this claim; researchers in this study found that participants who followed a Mediterranean diet (which contains many omega-3-rich foods like fish and nuts) had a lower risk for cognitive impairment.

With all this in mind, it is important that people who are trying to lose weight get enough healthy fats into their diet — even when they’re in a calorie deficit. According to most nutrition experts, the average person should get 20-35% of their daily calories from fats.7 However, some physique competitors may narrow down that range to 15-30% when they’re on a calorie deficit.8

Protein Requirements & Its Roles in Health

Every cell in the human body is made from protein, which is why it’s such an essential nutrient for muscle development and maintenance. Fitness and nutrition experts often emphasize the importance of protein, and for good reason: it aids in muscle building when consumed in excess calories and supports weight loss during a calorie deficit. This is why protein-rich meals such as chicken and rice are beneficial for weight loss.9

In addition to its aesthetic benefits (making folks leaner and more muscular), protein is hugely important for overall health. Protein helps support the body’s immune response, and it plays an important role in keratin formation, which is essential for healthy skin and hair.10

There is a wealth of research to show that a lack of protein can lead to uncomfortable symptoms and health conditions, including poor focus, food cravings, and wounds that are slow to heal.11

Research from Clinical Nutrition discovered that insufficient protein intake can have a marked effect on muscle strength and performance in elderly individuals — and while that study focused on the elderly, its results show just how valuable protein is for overall health and physical strength.

When a fitness enthusiast is in a calorie deficit, their body will burn anything it has stored to produce energy. This includes both fat and muscle. The best way to avoid this and maintain muscle mass is simply to eat enough protein.

Nutritionists recommend that people should get 10-35% of their daily calories from protein to meet their dietary needs. In the average person, that amounts to 0.7 to 1g of protein per pound of body weight.

However, research from the International Journal of Sports Nutrition and Exercise Metabolism found that those measurements were not enough for resistance-trained athletes like bodybuilders. Instead, they recommend that people who are used to weight training increase their protein macros to 1 to 1.4g of protein per pound, even during a cutting phase.

Understanding the Importance of Carbs While on a Calorie Deficit

Carbohydrates have gotten a bad reputation over the past several decades, with countless nutritionists and fad diet gurus demanding that people eliminate them from their diets. This is because the body breaks down carbohydrates and turns them into sugars — which, if left unused as energy, can be stored in the body as fat.12

Yet, many processed foods contain carbs, and therefore many people (even experts) believe that carbs make people fat.

A man is holding a cardboard box full of carb-rich french fries in his right hand, is eating a fry with his left hand, and has a face of uncertainty.

Source: SHOTPRIME via Canva.com13

The truth is a little more complicated than that. While it is true that processed foods can be bad for both a person’s health and waistline, carbs are not an “evil” food out to sabotage weight loss efforts. A study published in The Lancet even reported that low-carb diets (as well as high-carb diets) are associated with an increased risk of mortality.

In reality, carbs are a vital source of energy that everyone — but especially athletes and fitness buffs — need to have in their daily diet.

Research shows that eliminating carbohydrates can lead to uncomfortable symptoms like fatigue and constipation.14 This is why it’s recommended to get as much as 45-65% of daily calories from carbs. When someone is in a calorie deficit, it’s common for his or her carb intake to fall to the lower end, and carbs typically account for the calories left over after filling up on protein and fats.

However, not all carbs are created equal. While most people think of sweets, bread, chips, and pasta when they think of “carbohydrates,” there are plenty of fruits, vegetables, and grains that provide the body with healthy carbs.

For folks on a calorie deficit, this differentiation is crucial, as it can mean the difference between nutrient-rich, energy-dense meals that provide enough energy, or empty meals that leave people feeling hungry, sluggish, and unmotivated.

Can You Eat Junk Food Like Pizza, Sweets, Chips & McDonalds on a Calorie Deficit?

It should be evident that meeting macro requirements is crucial during a calorie deficit. Now, returning to the matter of whether you can eat anything on a calorie deficit, it’s also important to consider how a person meets their macro requirements.

It is possible to keep eating junk food and see results during a calorie deficit. In fact, people can eat nothing but junk food and see resulting in a calorie deficit (as evidenced by Mark Haub).

The common term used to describe this phenomenon is “IIFYM,” or “If it fits your macros.” Simply put, if someone on a diet is eating the appropriate amount of fats, protein, and carbohydrates and only eating enough calories to remain at a deficit, it doesn’t matter whether or not he or she eats burgers, ice cream, or donuts.15

“IIFYM” can be a comforting idea for people who find diets restrictive. They may not feel like they can resist their favorite sugary snacks for the time it takes to get a perfect body, so the knowledge that they can still indulge is a welcome relief.

However, if someone says that all foods that fit a person’s macros have the same nutritional value, run — that feeds into the big lie that people can eat anything on a calorie deficit without considering nutrients like vitamins, minerals, phytonutrients, and more.

Dieters who are serious about cutting body fat need to realize that their food is fuel. Just because a person can fill up on junk food during a calorie deficit doesn’t mean they should.

During a calorie deficit, the body is already producing less energy than it usually does, which can make even the healthiest fitness nut feel sluggish and tired.16 This is precisely why folks in a deficit should skip the sweets (maybe with a 21-day, no junk food challenge) and stick to healthy foods when they’re trying to cut calories.

For example, let’s compare the calories and macros in a cup of broccoli and one single donut.17,15

FoodBroccoli (1 cup)Glazed Donut
Fat (g)0.3g15 g
Protein (g)2.5g4 g
Carbohydrates (g)6g31 g

It’s clear that the donut contains much more calories and macronutrients — which means that one donut will bring someone in a deficit much closer to his or her nutritional limits for the day.

Gym goers who indulge in high-calorie sweets may find themselves eating less overall by the end of the day, which can result in less energy and greater cravings and hunger pains. If those same people eat healthier, nutrient-dense foods instead, they will be able to consume more and stay full and energized much longer.

How Many Calories Should You Eat on a Calorie Deficit?

The minimum thresholds for macros are a great way to ensure that a weight loss diet is on the right track. But of course, those thresholds are simply guidelines, designed to help as many people as possible.

No two bodies are exactly the same, and that means that a personalized diet plan is the best way to determine a person’s specific caloric needs.

The National Institute of Diabetes and Digestive and Kidney Issues offers this body weight planner tool to help people determine how many calories they should be eating. This tool is simple, intuitive, and can help anyone learn exactly how many calories they need to eat to meet their goals. To use the tool:

  1. Enter weight, sex, age, height, and activity level into the appropriate slots. Estimate your activity level by ranking your physical activity during work hours and off-hours as “very light,” “light,” “moderate,” or “heavy.”
  2. Enter your goal weight and the number of days in which you want to reach your goal. You can also use a calendar option to select the date by which you want to reach your goal.
  3. Calculate the percentage by which you plan to change your activity level. The tool offers a drop-down menu where you can add or remove physical activity from your routine.
  4. Finally, the tool will tell you how many calories you need to consume to maintain your current weight, reach your current goal, and maintain your goal once you get there.

Once gym goer determines their calorie needs for a cutting phase, they can figure out their macro thresholds. For example, if someone wanted to consume 1,200 calories each day, their macros may look like this:18

  • Fats: 240 calories (20% of total)
  • Protein: 420 calories (35% of total)
  • Carbs: 540 calories (45% of total)

Dieters who want to see results from their calorie deficit need to stick with this decreased intake for at least 2-3 weeks, then adjust their nutrition habits as needed.

The body needs time to adjust to this caloric decrease and start burning fat, which means it can take some time to see a drop on the scale. Don’t get too caught up with that number — it doesn’t tell the whole story of what’s going on in the body.

Tips to Eat Anything You Want in a Calorie Deficit

The response to whether you can eat anything on a calorie deficit isn’t simply “yes” or “no.” A more accurate answer would be, “Yes, but you should prioritize healthy foods.” That said, there is nothing wrong with someone indulging in a favorite treat every once in a while during a calorie deficit, as long as they meet their macros and stay within their calorie limits.

In fact, this might even make a dieter’s weight loss journey more manageable — and sticking with an effective routine is the most important part of any diet or fitness plan.

If a person wants to eat (mostly) anything they want while in a deficit, they’ll have to make sure they meet the following requirements:

  • They must meet the minimum macro thresholds for the day.
  • They must be in a caloric deficit (eating fewer calories than they’ve burned).
  • They must carefully consider their food choices and make sure they select healthier options most of the time.

Some people wonder if you can eat whatever you want if you work out. The answer is that weight loss primarily depends on creating a calorie deficit, with eating healthy foods being a secondary consideration. Plus, working out can allow you to eat more which in turn, means you might be able to eat a cookie or a few extra 100 calories while staying in a deficit.

Remember, food is meant to fuel the body and give it the energy it needs to get through the day. An occasional treat can be nice, but a healthy diet and proper nutrition will help people feel their best as they reach their weight loss goals.

Proper, balanced nutrition and regular movement can help anyone feel healthy, strong, and energized. People who persist will achieve their goals sooner than expected — and they will understand that while you can eat anything on a calorie deficit, it’s not advisable.


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15Cervoni MS, RD, CDCES, CDN, B. (2022, August 5). Broccoli Nutrition Facts and Health Benefits. Very Well Fit. Retrieved August 11, 2022, from <>

16Danahy, MS, RDN, A. (2020, November 13). How Many Calories Are in Glazed Doughnuts? Nutrients and More. Healthline. Retrieved August 11, 2022, from <>

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About the Author

Nathan Petitpas

Nathan has been a fitness enthusiast for the past 12 years and jumps between several types of training such as bodybuilding, powerlifting, cycling, gymnastics, and backcountry hiking. Due to the varying caloric needs of numerous sports, he has cycled between all types of diets and currently eats a whole food diet. In addition, Nathan lives with several injuries such as hip impingement, spondylolisthesis, and scoliosis, so he underwent self-rehabilitation and no longer lives with debilitating pain.