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What is a calorie deficit? Everything you need to know

What is a calorie deficit?

If you’re looking to lose weight you may have heard about calorie deficits. But do you know what it is and how they work? In this article we explain everything you need to know about calorie deficits and how they can help you on your weight loss journey.

What is a calorie deficit?

A calorie deficit is when you consume fewer calories through food and drinks than your body uses in daily activities and bodily functions. In simple terms it means you’re burning more calories than you're taking in.

A calorie deficit is often associated with weight loss. When your body doesn't get enough calories from your diet to meet its energy needs, it starts using stored fat as a source of energy, which leads to a reduction in body fat over time.

What calorie deficit is recommended for weight loss?

Creating a calorie deficit is a fundamental principle of weight loss and many diets. When you consistently maintain a calorie deficit, your body will use its energy reserves (primarily stored fat) to make up for the lack of calories. This results in weight loss.

To create a calorie deficit, people typically do one or more of the following:

  1. Reduce calorie intake: This involves eating less by choosing lower-calorie foods, controlling portion sizes, and making healthier food choices.
  2. Increase physical activity: Exercising more burns additional calories, contributing to the calorie deficit. This can include activities like walking, jogging, weight lifting, or any form of exercise that raises your heart rate and energy expenditure.
  3. A combination of both: Many people combine calorie reduction with increased physical activity to achieve a calorie deficit. This is often considered the most effective approach for sustainable weight loss.

To lose weight safely you’ll need to maintain a balance to ensure you’re getting the right amount of nutrition while having less calories. 

What should your calorie deficit be?

The recommended calorie deficit for weight loss can vary depending on several factors, including your starting weight, activity level, age, gender, and overall health.

If you’re trying to lose weight the you'll need to burn around 500 calories more than you consume. To lose weight the average man should have 1,900 calories a day and the average woman should have 1,400 calories a day.

How to safely calorie deficit

While creating a calorie deficit is the core principle of weight loss, it’s also important to focus on eating a healthy, balanced diet. You should be aiming for 5 portions of fruit and vegetables today, as well as other foods rich in nutrients.

A safe rate of weight loss is 0.5 to 1 kg (1 - 2 pounds) a week. Losing weight too quickly can be harmful to your health. Crash diets or extreme calorie restriction can lead to nutrient deficiencies.

Don’t cut too many calories

Cutting too many calories forces your body to burn muscle mass, rather than fat stores. This can lead to weakened muscles and lower body strength. Keeping a food diary or using a calorie counting app can help you keep an eye on how many calories you’re eating.

Don’t cut too much protein

Protein is a macronutrient that’s needed by the body for growth and repair. It also contributes to muscle strength and so cutting too much protein can affect your muscles. Find healthy swaps for your favourite snacks here as well as more ways to get the right amount of protein in your diet.

Stay hydrated

The body is made up of around 70% of water which is why it’s important to keep hydrated. Drinking 6-8 cups a fluid a day helps keep you hydrated. Choosing water, low sugar and low fat drinks can help you maintain a calorie deficit and lose weight.

Why am I not losing weight on a calorie deficit?

If you're not losing weight despite being in a calorie deficit, there could be several reasons for this weight plateau or lack of progress. These can include:

  • Inaccurate calorie tracking - you could be underestimating the number of calories you’re having and overestimating the amount you’re burning through exercise
  • Stress - High stress levels can affect your hormones making it harder to lose weight
  • Sleep - Not getting enough sleep can lead to weight gain
  • Your metabolism - Your body may have adjusted to the lower calorie intake by slowing down your metabolism
  • Muscle gain - If you’re doing strength training exercise you may be gaining muscle mass which is denser than fat
  • Weight plateau - It's common to experience periods of slower or stalled progress during a weight loss journey
  • Hidden calories - Be mindful of hidden sources of calories in your diet, such as cooking oils, sauces and dressings
  • Lack of consistency - If you're only sticking to your plan some of the time your progress may be slower

If you continually find that losing weight is difficult, you can speak to your GP or a dietician. They can help you make a diet and exercise plan, or adjust your own. They may be able to recommend weight loss treatments to help you. Remember that weight loss is a journey, and it may take time and effort to achieve your desired results.

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Keeping track of your progress, adjusting your calorie deficit as needed, and considering other factors such as stress management, sleep, and overall well-being can contribute to a successful and sustainable weight loss journey. There are also weight loss treatments available which can be used alongside a healthy balanced diet and exercise routine to help you on your weight loss journey. Lloyds Online Doctor also has lifestyle advice to give you the knowledge and support you need to succeed. 



    Authors and editors

    Reviewed and updated by: Our clinical team Date reviewed: 15-05-2024