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How Much of a Calorie Deficit Is Too Much and Why?

how much of a calorie deficit is too much

If you want to lose fat, you need to reduce your calories. But how much of a calorie deficit is too much? If you keep your daily calorie count above 1000 calories and don’t cut by more than 1,000 calories, you should lose weight safely. 

The key is to know how many calories a day you should eat so that you can lose it … and keep it off. Let’s take a closer look at calories and what it means to be in a calorie deficit. 

What is a calorie?

A calorie is a specific measure of energy. In short, it takes 1 calorie to heat 1kg of water by 1 degree Celcius. We use “calories” to refer to the amount of energy extracted from eating food or energy burned while exercising.

The nutrients in food can be broken down into three macronutrients: carbohydrates, fats, and proteins. These macronutrients contain the following calories per gram:

  • Carbs — 4 calories per gram
  • Fats — 9 calories per gram
  • Protein — 4 calories per gram

It’s important to remember that your body does not always treat calories equally. Some calories are processed very quickly (for example, simple sugars) and others take much longer to process (such as the calories in wholegrains and vegetables).

Why do you need calories?

Like a car needs fuel to run, our bodies need energy to maintain life. Regardless of your activity level, you’re always burning calories. The body uses calories to:

  • Power your brain and central nervous system
  • Keep your heart beating and blood pumping throughout your body
  • Power the respiratory system and keep you breathing
  • Keep all your organs functioning and your endocrine system operating as it should
  • Power your muscles (both voluntary and involuntary muscles)
  • Conduct cellular repair and growth 

The total number of calories burned to maintain basic life is known as your Basal Metabolic Rate (BMR). One of the ways to work out an approximation of your BMR is to calculate your calories burned sleeping

When sleeping, your body is resting and only performing vital functions which will give you a good indication of how many calories it needs to maintain life. For more on this, read how many calories do you burn doing nothing

How many calories do you need a day?

How many calories you need in a day depends on your height, weight, and sex. While everyone has different metabolic rates, most people of similar body compositions require about the same number of daily calories to function.

According to the 2015 to 2020 Dietary Guidelines for Americans, we need from 1,600 to 2,400 calories daily. Men, in particular, need 2,000 to 3,000 calories every day. While this is a large range, most people land on the lower end of the spectrum in terms of how many calories they really require. 

The best way to work out how many calories you need is to use a calories a day calculator to work out your daily calorie requirement if you would like to lose weight. You can also use this calculator if you want to know how many calories do I need to gain muscle? Work out your daily calorie requirement and add 10 – 20% calories (from healthy sources.)

What is a calorie deficit?

In short, a calorie deficit means that you burn more calories throughout the day than you consume. For example, if your body needs 2,000 calories a day to maintain your weight, eating a diet that is 1,900 calories would be a calorie deficit. Theoretically, if you consistently eat 1,900 calories a day, you’ll very gradually lose weight.

What is a good calorie deficit to lose weight?

A pound of fat is approximately 3,500 calories. To lose a pound, you would need to burn 3,500 more calories than you consume. 

Generally, weight loss of 1-2 Ibs per week is considered to be safe for your health. This works out to a calorie deficit of between 3,500 – 7,000 calories a week. 

A safe way to reach this goal is to reduce your calorie intake by 500 – 1,000 calories a day. Health professionals recommend cutting 500 calories a day to avoid feeling hungry and “deprived.” 

Although you can lose weight quickly by eating less than 1,000 calories a day, it should only be under medical supervision and as part of a weight loss management plan. 

Rapid weight loss usually means rapid weight gain (plus a few extra pounds), as soon as you come off your diet. Your weight will “yo-yo” up and down — hence the term “yo-yo dieting.”

The best way to lose weight and keep it off is to bring changes to your daily diet and exercise habits and build them into a lifestyle that you can easily maintain. 

How much of a calorie deficit is too much?

Reducing your daily calorie intake by 1,000 calories will help you lose weight but, in the long run, the weight loss will be too rapid which can put your health at risk. Therefore a calorie deficit of 1,000 calories is generally considered too much. 

There may be times when a calorie deficit of more than 1,000 calories is required. However, once more, this should only be done under medical supervision and as a part of a healthy weight management plan. 

Here are some of the signs that may indicate you’ve cut too many calories or perhaps not eaten enough.

Immediate signs of too few calories

  • Lack of energy and feeling tired most of the time
  • Lightheaded and dizzy
  • Low blood sugar — causing shakiness, anxiety, sweating, mood changes, and weakness

Long-term effects of severe calorie restriction

Apart from your physical health, eating too few calories over a long period can also have a negative effect on your mental health and emotional well-being. Here are some of the ways that your health can be affected.

A BMI that’s less than 18

Eating too few calories a day for a long period of time can cause rapid fat and muscle loss. This can result in you being underweight or having a BMI (Body Mass Index) less than 18. 

Although most of us would like to weigh less, being underweight is associated with many health issues and risks because your body will not have enough nutrients and energy to maintain good health.  

This includes:

  • An increased risk of developing osteoporosis
  • A weakened immune system 
  • Fertility issues
  • Low iron levels and a risk of becoming anemic
  • Hair loss and hormonal issues 

Fluctuating weight

Rapid fat loss often results in rapid weight gain. In fact, studies have shown that 1 in 3 people who experience “yo-yo” dieting will regain more weight than they have lost and that weight regain is the general rule for most dieters. 

The rapid fat loss followed by rapid weight gain can wreak havoc on your mental health and self-esteem. It’s very common for “yo-yo” dieters to have disordered eating habits and an unhealthy relationship with food. 

Apart from that, it has been found that 78% of people who have weight fluctuations are more likely to develop type 2 diabetes. It has also been found a history of yo-yo dieting results in a higher body fat percentage

A weakened immune system

The body needs macro and micronutrients to stay healthy. A severely restrictive diet will also restrict your intake of vitamins and minerals that your body needs to keep your immune system strong and build and repair cells. As a result, you might be frequently ill or take much longer to recover from illness.

Nutrient deficiencies and fatigue

If you are on a very low-calorie diet for a long time, you might not eat enough for your body to get all the nutrients it needs to keep you healthy and strong. Nutrient deficiencies might include low iron levels, and vitamin, and mineral deficiencies. 

Along with deficiencies in essential nutrients, if you’re not eating enough calories, you might also struggle with fatigue and a lack of energy to exercise. 

From the above, we can see that losing too much weight too quickly, can have severe effects on your health and make it very challenging to maintain a healthy weight. The best way to lose weight and keep it off is to build sustainable habits so that it becomes part of your lifestyle. 

5 steps to healthy weight loss

There are two things you can do to achieve a calorie deficit: reduce your calorie intake and burn more calories through exercise.

Keep in mind that it’s easier to reduce the number of calories you eat than try to burn them off through exercise. Follow these 5 steps to lose weight safely

Step 1 — Calculate how many calories you should eat to lose weight safely by using this calories per day calculator.

Step 2 — Eat whole unprocessed foods: meat, dairy, vegetables, eggs, fruits, nuts, and seeds

Step 3 — Follow a meal plan and track your meals to stay accountable. A good place to start is this 7 Day Meal Plan 1500 calories

Step 4 — Prepare your meals yourself so that you can control the calorie content

Step 5 — Track your weight or your measurements to see your progress

7 easy ways to reduce your calories

If you want to reduce your calorie intake, there are a few things you can do. Here are 7 of the best ways to reduce your calorie intake.

Cut out sodas and sweet drinks

Sodas, smoothies, and fruit juices contain many calories. For example, 1 can of cola contains approximately 139 calories and a glass of grape juice contains 152 calories. Opt for low-calorie or no-calorie options.

Eat whole, unprocessed foods

Choose whole, unprocessed foods. Processed foods often contain sugar and additional carbohydrates to improve and balance out the flavors. These in turn will add more calories. Opt for unprocessed whole foods to ensure that there are no “hidden” calories.

Fill up on vegetables

Vegetables are naturally low in calories and high in fiber. Not only will they help with providing daily nutrients but they can also help you feel full. For example, eating a huge salad with your portion of chicken will fill you up versus just eating the chicken. 

Eat more protein

Protein is crucial to everyone’s diet for several reasons. It helps muscles repair, food digest, and regulates your hormones. However, it is also important in dieting because it helps you feel full for longer. Additionally, it reduces muscle loss so that the weight you lose is from fat instead of muscle.

Don’t forget the healthy fats

Although a gram of fat contains more calories, healthy fats make you feel fuller for longer and can help in reducing your overall calorie count. Adding healthy fats to the diet is a great strategy to prevent hunger and snacking. For more on fats read How much fat per day to lose weight. 

Practice portion control

It can be challenging to control your portions, especially if you’re feeling hungry but portion control can go a long way in helping you stick to your diet. Invest in a small kitchen scale to weigh your portions if you’d like a more precise measurement. Another tip is to use smaller plates and bowls for your meals. This will naturally reduce the amount of food you can eat in one meal. 

Drink more water

Finally, aim to increase your water intake and drink water throughout the day. If you don’t like still water, drink sparkling spring water instead. You can also add ice and lemon or mint leaves to help. 

Calorie deficit but not losing weight – why?

If you are not losing weight in a calorie deficit, here are some things to check that should help you work out why this might be occurring. 

Track your calories to check if you are in a deficit

We tend to underestimate how many calories are in a serving. As a result, it is a good idea to manually track your calories to ensure you stay in a calorie deficit. Tracking calories in an app or a program like Microsoft Excel will help you get started. It will also help you be more aware of what you’re eating and snacking. The odd cookie as a snack might just be the reason why your weight is not budging. 

Your calorie deficit is not enough

Aim for a deficit of 500 – 1000 calories to safely lose 1 -2 pounds of fat in a week. Add in daily exercise to help you burn more calories. Have a look at our calorie calculators to work out how many calories your burn doing your favorite activities from walking to running, to weightlifting and Zumba. 

You’re overestimating how many calories you burn

If you are relying on exercise to burn calories instead of monitoring your intake, you can potentially be overestimating how many calories you are burning during exercise.

Even though using a calculator can help, there are many factors that can affect the calories burned in a session.

The best way to make sure you are in a calorie deficit is to reduce how many calories you are consuming rather than relying on how many you are burning. 

You’re not weighing yourself consistently

When it comes to weighing yourself, consistency and accuracy is the key. In one day, your weight can fluctuate by a good couple of pounds due to a number of factors. These include:

  • How much food and liquid you’ve consumed
  • If you’ve been to the bathroom
  • Your hormonal cycle 
  • Whether you’re retaining water

It’s best to weigh yourself first thing in the morning after you’ve been to the bathroom and before you eat. 

If you use different scales to weigh yourself, you might also get different readings. In addition, sometimes your weight can change depending on where you weigh yourself on the floor. For example, you might weigh one weight in the corner of the room but could be 2 pounds heavier in the middle of the room. It’s best to weigh yourself on the same scale, in the same spot, at the same time. 

If you have an unhealthy relationship with weight and weighing yourself, then it’s best to rely on measurements to track your progress. For example, measure your waist, hip, and thigh measurements once a week. Try to measure yourself at the exact location every time as a couple of inches out, will give you a different measurement. 

You’ve hit a temporary plateau

When you first start a diet, weight loss might happen fairly quickly due to the excess fat and the change. However, the closer you get to your “ideal” weight, the slower the weight loss might go and you might even hit a plateau. 

If your numbers are correct, then the key here is to persevere with your diet and exercise plan. In a week or two, the weight should once more start to drop off as you burn into those final few pounds. 


  • How much of a calorie deficit is too much? Cutting by more than 1000 calories and eating fewer than 1,000 calories
  • Eating too few calories for a long period may have negative effects on your health and well-being. 
  • Calculate a calorie deficit of between 500 – 1000 calories a day and combine it with exercise for the best results.
  • Keep track of what you eat
  • Eat whole unprocessed foods and drink plenty of water
  • Measure yourself first thing in the morning, after you’ve been to the toilet and before you eat breakfast. Use the same scale in the same position.
Lose weight through behavior change, not fad dieting

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