By Catherine Renton published
You’ve probably heard that you need to create a calorie deficit to lose weight. But what does this involve, and why is a calorie deficit necessary for weight loss?
A calorie deficit occurs when the number of calories a person consumes in a day is smaller than the number of calories they burn. The body needs to burn a certain number of calories to perform its daily functions, including exercising with the best exercise machines to lose weight. How many calories you need each day varies depending on age, sex, physical activity levels, height, weight, and body composition.
We’ve spoken to experts in nutrition to give you the low down on what you need to know about a calorie deficit, including what it is, and what happens when your calories plateau.
Calorie deficit to lose weight: what it means
If you consume fewer calories than your body needs to perform all its necessary functions, you create a calorie deficit. Nutritionist David Starr explains what happens when you create a calorie deficit. “To make up the difference, your body burns energy from your fat stores, and so you lose weight. Governments in the U.S. and the UK recommend an initial, gradual weight loss strategy of one to two pounds a week through a small energy deficit each day. Gradual weight loss allows more time for people to form the habit of eating fewer calories.”
To create a calorie deficit, you need to know your maintenance calories. Maintenance calories are precisely the number of calories your body needs to support energy expenditure. You can use calorie calculators like the Body Weight Planner from the National Institute of Health to guide you. Such calculators estimate your maintenance calories based on your weight, sex, age, height, and physical activity level.
However, it should be noted that not all nutrition experts or researchers agree that shedding excess weight is as simplistic as cutting a certain number of calories per day. Not all calories are created equal. For example, a breakfast consisting of a 500-calorie muffin made with refined sugar and white flour will have a very different effect on your body than a 500-calorie bowl of cooked porridge topped with blueberries and nuts. That's not to say that calories don't matter, but they're not the sole factor of weight management.
How do you create a calorie deficit?
Once you know your maintenance calories, you can calculate your calorie deficit. For example, if you use 2,000 calories today but only take in 1,800, you have a deficit of 200 calories. Research suggests that a calorie deficit of 500 calories per day is sufficient for weight loss and is unlikely to significantly affect your hunger or energy levels. However, be careful not to cut your calories by too much. Diets with a very low daily energy intake can sometimes lead to nutritional deficiencies and should not be followed unless under medical supervision.
You can create a calorie deficit by reducing calories eaten, increasing activity levels, or both. Some people find it easier to create a calorie deficit through diet alone rather than exercise, as they may not have the time, energy, or motivation to exercise every day.
David Starr says, “It is easiest to create a calorie deficit by slightly reducing portion sizes, increasing the time between meals, or exchanging some higher calorie ingredients for lower-calorie alternatives. It has been shown that most successful common weight loss plans work because they create a calorie deficit through one of these methods.”
Health strategist Hayley Field recommends that rather than fad diets or intense exercise, the safest way to achieve a calorie deficit would be:
- Reduce calories but increase food volume: Concentrate on getting enough protein and filling up on nutrient-dense, low-calorie foods such as vegetables, fruits, salads, and high fiber foods like whole grains.
- Increase activity slowly: Walking is a fantastic place to start. It’s accessible, free, and if you do it consistently, you can see results!
- Weightlifting: This is great for building muscle which burns more calories and ensures that you maintain your lean muscle mass while still losing fat.
- Getting better quality sleep: Lack of sleep can affect the hormones responsible for appetite regulation, making you hungrier, more irritable, and more likely to make poor decisions around food.
- Don’t set daily targets: Flexibility is key to a sustainable deficit. So rather than stressing whether they've hit a daily calorie target, I get my clients to look at their deficit over the week or even the month.
What happens when you’re no longer in a calorie deficit?
Bear in mind that the closer you are to your weight goal, the smaller the deficit between the calories needed to maintain your weight and the number required to support your ideal weight. That means slower results.
Field explains that your weight loss will slow over time, even with a calorie deficit, and you may reach a plateau or start to gain weight. “As you lose weight, your calorie needs will be less, so a 500-calorie deficit when you’re 80kg suddenly becomes a much smaller deficit when you reach 70kg. And the longer you stay in a deficit; the more your body adapts to being efficient with the fuel you’re giving it. Imperceptible things such as fidgeting less, walking a bit slower, slouching in your chair - these are all your body’s way of conserving energy.”
Field advises that instead of rushing to cut calories further to make the deficit more significant, you can monitor your fat loss and increase calories to the maintenance level when you’ve lost around 10% of their total body weight. “This encourages the body to stop being so efficient with the fuel you are giving it and gives the metabolism a chance to return to normal. You also get a psychological ‘break’ from dieting. We do this for 1-2 weeks, return to the deficit and repeat the cycle until they reach the fat loss they were hoping for.”
Catherine is a freelance journalist writing across titles such as Verywell Health, Healthline, The Daily Telegraph, Refinery29, Elle, and Vogue. She specializes in content covering health, fitness, wellness, and culture.
A once reluctant runner, Catherine has competed in 30 running events in the past five years and looks forward to one day running the London Marathon.
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