If you want to lose or gain weight, then you may have seen or heard the terms “surplus” and “deficit”.
The primary difference between a calorie surplus and a calorie deficit is their impact on body weight. Calorie surplus means eating more calories than needed, leading to weight gain. Calorie deficit means eating fewer calories than required, resulting in weight loss
While there are differences between these two calorie approaches, most people will eventually spend some point in both phases to optimize lean muscle growth and reduce body fat.
So it’s helpful to understand what they are and how to implement them correctly.
- A calorie surplus and a calorie deficit will have opposing effects on your weight, metabolism, hormones, performance, and energy levels.
- An optimal calorie deficit should be around 500 calories a day, which may result in losing 0.42-0.82% of body weight per week.
- An ideal calorie surplus should be 10-20% above maintenance calories, where you should expect to gain 0.25-0.50% of body weight per week.
What Is A Calorie Surplus?
A calorie surplus involves eating more calories than you need to maintain your weight, which provides your body with excess energy to put towards gaining mass (muscle and/or fat).
This eating pattern is often associated with a “bulking” phase in bodybuilding or weightlifting, where individuals need to eat more to build muscle mass.
However, it should be noted that a calorie surplus by itself will not automatically lead to muscle gain; you would also need to focus on your macronutrient intake (carbs, fats, and protein) and follow a resistance training program.
A calorie surplus in the absence of those other factors will simply lead to fat gain.
What Is A Calorie Deficit?
A calorie deficit involves eating fewer calories than required to maintain your weight, causing your body to have to use its own resources (preferably fat) for fuel and resulting in weight loss.
This eating pattern is often associated with a “cutting” phase in bodybuilding or other aesthetic sports, where individuals want to lose fat.
However, it should be noted that if you want to maintain your current muscle mass as you lose weight, then you will also have to focus on your macronutrient intake (carbs, fats, protein) and follow a resistance training program.
- For more information on macros, check out our Beginner’s Guide To Macro Tracking.
Understanding Energy Balance: Surplus vs Deficit
Energy balance means that the number of calories you eat/drink (energy intake) is the same as the number of calories you burn (energy expenditure).
When your intake and output are equal, you will have achieved “energy balance” and your weight will remain stable.
This also explains why we use a Total Daily Energy Expenditure (TDEE) to calculate your maintenance calories because you will maintain your weight when you’re eating the same number of calories as you’re burning.
If your goal isn’t to maintain your weight, then you’ll want to tip the scales in the direction of your goal by changing your intake or output.
- Calorie Deficit = Intake Less Than Output
- Calorie Surplus = Intake More Than Output
Factors That Influence Weight Management
Gaining, losing, and maintaining weight is affected by multiple factors, some of which are within our control (diet, lifestyle, sleep, and exercise) and others which are out of our control (age, gender, genetics/hormones).
The main factors influencing weight management are:
- Age: As you age, your body burns fewer calories; which is mainly related to decreases in muscle mass as you age. As a result, you will likely burn more calories when you are 25 than you will when you turn 35.
- Gender: Men and women have different body compositions, with men having a higher potential for muscle mass, which allows them to burn more calories than women.
- Genetics: Your genes and the presence/lack of hormones determine how you use and store energy, and how quickly or slowly you gain or lose weight.
- Work: The job you do influences how many calories you burn in a day, so if you have a sedentary job you will burn fewer calories than if you had an active job involving manual labor.
- Sleep: Lack of sleep (sleeping less than 7-9 hours) impacts hunger and appetite hormones. This can lead to weight gain by causing you to feel hungrier than normal. For example, if you sleep 5 hours for 2 nights in a row, you may feel the urge to snack more the next day.
- Physical Activity: The type of sport you do (endurance, strength/power, or aesthetic), your training history, and your training volume will impact how many calories you burn during exercise. For example, if you are an endurance athlete training 15 hours per week for an ironman, you will burn more calories overall than someone training 6 hours per week.
- Lifestyle: Unhealthy eating and drinking habits (including alcohol consumption) impact your calorie intake. If your diet consists of burgers, chips, or pizza every other day, you’re more likely to gain weight as these foods are calorie dense.
Key takeaway: Each person will have different caloric needs based on these factors, but the principles for changing your body weight (using a deficit or a surplus) are the same for everyone.
9 Differences Between Calorie Surplus vs Calorie Deficit
The main differences between a calorie surplus and a calorie deficit are:
1. Energy Balance
A calorie surplus means you will be in a positive energy balance, taking in more calories than you need to maintain your weight.
A calorie deficit means you will be in a negative energy balance, taking in fewer calories than you need to maintain weight.
2. Physical Changes
Another key difference between a calorie surplus and a deficit is the physical changes you will experience over time.
A consistent calorie surplus will cause you to gain weight, increase your muscle and/or fat mass, and make your clothes feel and look tighter.
A consistent calorie deficit will cause you to lose weight, decrease your fat mass (and potentially muscle mass), and make your clothes fit and look looser.
3. Metabolic Changes
There will also be differences in how your metabolism will be impacted because your metabolism will respond to changes in your calorie intake over time.
With a calorie surplus, your weight will increase and your body will need more energy to support muscle growth and maintain bodily functions over time.
This means that your resting energy expenditure (how many calories your burn at rest) will increase and you will burn more calories per day.
With a calorie deficit, your weight will decrease and your body will have less available energy to support your muscles and maintain basic functions, so it will try to conserve energy by slowing down your metabolic rate.
This means your resting energy expenditure will decrease and you will burn fewer calories per day.
4. Hormonal Changes
Hormonal changes will also be different with a calorie surplus and a calorie deficit because your calorie intake will impact your energy use/storage hormones and hunger/satiety hormones.
A calorie surplus can result in increased levels of insulin and leptin (satiety hormone), which both support fat storage and higher levels of other hormones such as testosterone that can support muscle growth.
- Related article: Does Bulking Increase Testosterone? What Science Says
On the other hand, a calorie deficit results in lower levels of leptin (causing you to feel less satisfied), and it can also lead to lower levels of testosterone and thyroid hormones.
Consequently, this may result in fat loss, muscle loss, and a slower metabolism.
5. Performance & Endurance
Another difference is the effect your calorie intake will have on your sports performance and your ability to recover from training.
In a calorie surplus, you will likely be able to lift heavier weights and work out for longer as you will have more available energy to fuel training and to put towards recovery.
In a calorie deficit, you will have less energy to put towards training and recovery, particularly for high-intensity exercises like sprinting.
This means that you may get fatigued more quickly and take longer to recover, so you will likely have to adjust your training by lifting lighter weights, performing fewer sets or reps, or switching to shorter workouts.
6. Nutrient Balance
Being in a surplus or deficit affects nutrient balance differently because, with a higher calorie intake, you will have more “wiggle room” to include foods that may be less nutritious, whereas when your calories are lower you will have less “wiggle room” for these foods.
In a calorie surplus your calorie intake is higher, which leaves you plenty of room for foods that are nutrient-dense (i.e. salmon, avocado, rice) and processed foods that are high in fat, salt, and sugar (i.e. donuts, ice cream, french fries).
Most people in a surplus choose to incorporate a mixture of nutrient-dense and less nutrient-dense foods to help hit their calorie target more easily.
In a calorie deficit, your calories are lower which makes it harder to fit in these processed foods without going over your calorie target.
For this reason, your food choices will be more limited to nutrient-dense, lower-calorie foods like lean meats, leafy green, and sweet potatoes rather than fun foods.
Mood may also differ between a surplus and a deficit, though mood can be quite subjective, as it depends on the psychological state of a person.
When you’re in a surplus you have more freedom to eat whatever you want so it can be more enjoyable and exciting to be in a surplus.
However, if your calorie target is high enough that you find it challenging to adhere to then you may start to feel unmotivated and discouraged, and eating may feel more like a chore.
When you’re in a calorie deficit it’s common to feel grumpy, unmotivated, or even sad because of the lack of freedom with food.
Those who are in a consistent calorie deficit sometimes find themselves becoming obsessed with thinking about food because they’re hungry and deprived.
8. Social Life
Your social life can also look different depending on whether you’re in a surplus or a deficit because many social outings revolve around food.
When you’re in a deficit you may be more likely to socialize around food and drink because you have more freedom to participate.
When you’re in a calorie deficit you might avoid social events that involve eating and drinking because you know it will tempt you to participate and perhaps not hit your calorie target.
9. Energy Levels
Lastly, your energy level will be drastically different between a surplus and a deficit because your calorie intake will affect how energized you feel.
In a caloric surplus, you will have more available energy (glycogen) to fuel your body so you will likely feel much more energized. That said, if your surplus is really high (i.e. 1000-calorie surplus) then you may feel lethargic instead.
In a calorie deficit, you will have less available energy for your body, which may result in feeling more tired and fatigued during your day and less motivated to do everyday activities.
Calorie Deficit For Weight Loss
When To Consider A Calorie Deficit
You should consider a calorie deficit if:
- You are unhappy with your weight (maybe you’re overweight/obese) and you want to improve your health by losing weight.
- You are a competitive athlete and you want to improve your performance (speed, strength/weight ratio) by changing your body composition (losing fat and retaining muscle).
- You are a bodybuilder and you want a lean physique by reducing fat and retaining muscle.
Is A Calorie Deficit Safe?
A calorie deficit can be safe and even healthy for you if you do it the right way; however, if you’re too aggressive or stay in a deficit for too long then it can become unsafe.
A healthy and sustainable deficit for most people would be a 500-calorie deficit, with gradual weight loss (around 0.5-1 pound a week), allowing for a safe and realistic target of a reduction in body weight by 5-10% over 3 months.
For example, if I weigh 160lbs and I implement a 500-calorie deficit, then I could realistically expect to lose 8-16lbs over the course of 3 months.
An unsafe way to implement a deficit would be to create too large of a calorie deficit (i.e. 1000-calorie deficit), for more than 3 months. This can lead to negative health consequences such as:
- Malnutrition, which can bring about nutrition deficiencies because of having to cut out certain foods in order to hit your calorie target.
- Rapid muscle loss and poor recovery, as your body will be deprived of the energy that is needed to retain muscle and to recover.
- Imbalanced hormones, such as low testosterone and increased ghrelin (hunger hormone).
- Slower metabolism, as your basal metabolic rate will decrease after being in a prolonged calorie deficit causing you to burn fewer calories per day.
- Becoming underweight or anorexic, especially if you already have a naturally low weight.
The only scenario where someone would potentially opt for extreme, unhealthy deficits is in the case of a bodybuilder wanting to lose weight fast to look as lean as possible, for a short period.
- Related Article: Can You Undereat & Not Lose Weight?
How To Determine Calorie Deficit
There are 3 easy steps to estimate your deficit:
- First figure out your maintenance calories. You can use this Total Daily Energy Expenditure (TDEE) calculator, which estimates the number of calories you need to maintain your weight.
- Stick to your maintenance calories for 10 days to check that your weight remains stable. You can track your weight (weigh yourself at the same time of day twice weekly) to monitor the trend.
If your weight remains stable, then you can progress to the next step. If your weight doesn’t remain stable (goes up or down) then adjust your calories accordingly (+/- 100 calories) to find your true maintenance before moving on to step 3.
- Subtract 250-500 calories from your maintenance calories. If you want to retain as much muscle as possible and have higher energy levels for training, then start by subtracting 250 calories. If you want to speed up the process and feel fine when you decrease by 500 calories, then do that instead.
Realistic Results From A Calorie Deficit
Weight loss is rarely a linear process, so the results you achieve from a calorie deficit will vary from person to person. Some weeks you may lose weight, and other weeks your weight may remain the same.
This is normal and occurs because of individual nuances in starting weight, biology, exercise levels, and lifestyle.
In general, you can expect to lose 0.5-1lbs per week with a 500-calorie deficit because this adds up to a 3500-cal deficit over the course of a week, and 3500 calories is equivalent to roughly a pound.
This differs slightly if you are a competitive bodybuilder, powerlifter, or weightlifter because slower rates of weight loss are needed to retain as much muscle as possible as you lose fat. In these situations, the expectation would be to lose less than 0.5% of body weight per week.
Calorie Surplus For Weight Gain
When To Consider A Calorie Surplus
You should consider a calorie surplus if:
- You are recovering from an illness or injury, and need additional calories to support your recovery.
- You are a bodybuilder wanting to improve how you look by building muscle, so you need additional calories to encourage muscle growth.
- You are an endurance athlete, and you need extra calories to maintain energy levels during extended periods of exercise to prevent fatigue.
- You are a powerlifter who wants to become more competitive by going up a weight class.
Is A Calorie Surplus Safe?
A calorie surplus is safe if you do it in a healthy way; this means reaching for nutrient-dense foods more than processed foods, setting a realistic surplus within 10-20% of maintenance calories, and not staying in a surplus for too long.
An unsafe way to implement a surplus would be to overeat on less nutritious foods for 6+ months (such as sweets, biscuits, juices, fried foods, hot dogs, salami, corned beef, jerky, and bacon), and having too large of a surplus (i.e. 1000+ calories above maintenance).
This is because:
- Excessive calories can lead to excess fat gain, making it difficult to get back in shape if you compete in physique sports or strength sports.
- Eating an excess of foods high in added sugar and refined carbs raises glucose levels. This means that you can have higher levels of sugar in the blood, which can lead to insulin resistance. You should aim to eat no more than 10% of total calories from added sugar.
- Eating a lot of foods high in saturated fats increases the risk of developing cardiovascular issues. You should aim to eat no more than 10% of total calories from saturated fat.
Related Article: How Big Should My Calorie Surplus Be? And, What Is Too Much?
How To Determine Calorie Surplus?
There are 3 simple steps to determine your surplus:
- First determine your maintenance calories. You can use this Total Daily Energy Expenditure (TDEE) calculator to estimate the number of calories required to maintain your weight.
- Stick to your maintenance calories for 10 days to check that your weight remains stable. Ensure you weigh yourself at the same time of day, twice weekly.
If your weight remains stable, then you can progress to the next step. If your weight doesn’t remain stable (goes up or down) then adjust your calories accordingly (+/- 100 calories) to find your true maintenance before moving on to step 3.
- Add 10-20% to your maintenance calories. If you want to minimize fat gain as much as possible then start by adding 10%; if you want to gain weight more quickly and you don’t care if you gain some fat, then add 20%.
Related article: How To Know If You Are In A Calorie Surplus
Realistic Results From A Calorie Surplus
The results that each person achieves by implementing a calorie surplus will differ based on their rate of progress, starting weight, exercise levels, lifestyle, and biology. However, if you’re in a true surplus then you will gain weight.
It’s normal for weight to increase one week and stay stable the next, this doesn’t necessarily mean that you aren’t progressing. For this reason, it’s important to monitor how your body is responding over time (2-4 weeks) rather than just week-to-week.
In general, you can expect to gain around 0.25-0.50% of bodyweight per week, or 1-2% per month, if your surplus falls within the recommended 10-20% and your maintenance calorie calculations are accurate.
If you notice your weight goes up more than this, then that means you are gaining weight too quickly, likely in the form of fat rather than muscle.
- Related Article: How Long Should You Bulk For?
Should You Be In A Calorie Surplus or Deficit If You Want To Do A Body Recomposition
Body recomposition is a term to describe losing fat and gaining muscle (at the same time) to shift your body composition to a leaner, more muscular physique.
“Unlike a standard diet, body recomposition is a lifestyle in which fitness and nutrition techniques lead to beneficial changes in your body’s ratio of fat to muscle. Recomposition means “to form something again or in a different way,” hence the term body recomposition”Jillian Kubala and Amy Ritcher, Registered Dietitians
Research shows that different nutrition techniques (such as a high protein diet, calorie deficit, calorie surplus, and specific nutrient timing) can lead to body recomposition.
- Check Out: Body Recomposition Calculator: Lose Fat While Gaining Lean Muscle
As such, if you want to do a body recomposition, it is likely a combination of things that will help you achieve this (and not a calorie surplus or deficit alone).
So, based on this, my advice would be to:
- Establish and focus on one goal instead of having 2 simultaneous goals. Decide whether you want to gain muscle or lose fat first, then pursue the other later on. In doing so, you’ll be able to recomp your body at a faster rate than trying to lose fat and gain muscle at the same time.
- Implement 2-3 strength training sessions per week to either retain or build muscle.
- Eat between 0.7-1.2 grams of protein per pound of bodyweight per day to support muscle growth and recovery.
- Monitor your progress by tracking your macros and exercise (at least initially). You can even take body measurements or use bioelectrical impedance scales to measure fat and muscle percentage. This way you will have a rough idea if your body composition is changing.
Check out our guide on Bodybuilding Meal Plans, which will help you set up your weekly eating plan.
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About The Author
Giulia Rossetto is a qualified Dietitian and Nutritionist. She holds a Masters in Human Nutrition (University of Sheffield, UK) and more recently graduated as a Dietitian (University of Malta). Giulia aims to translate evidence-based science to the public through teaching and writing content. She has worked 4+ years in clinical settings and has also published articles in academic journals. She is into running, swimming and weight lifting, and enjoys spending time in the mountains (she has a soft spot for hiking and skiing in the Italian Dolomites).
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