How many calories do you need to eat a day to lose weight? Try our calculator to find out

Want to lose weight? Understanding how calories actually work is key

You may have a pretty good idea of how much you should be eating per day. Or you might not have a clue and simply tuck into whatever you fancy.

But understanding how calories – a unit of energy – actually work can be vital if you’re looking to change your weight or even just maintain it.

To determine how many calories you should be eating, input your details into the handy calculator, which takes exercise levels, height and age into account.

It will then tell you the calories you need per day to maintain your current weight. Or, if you want to lose weight, there’s the option of adding a goal weight and number of weeks you want to achieve this in. The calculator will then let you know how far you need to drop your calorie intake to achieve this.

Official calorie advice has barely changed since the 1990s, when women were told to stick to 2,000 calories a day to keep a steady weight, while 2,500 were recommended for men.

For women, this can look like a slice of toast with peanut butter and yogurt with fruit for breakfast, a chicken wrap with salad and an apple for lunch and a beef stir fry with noodles for dinner, as well as two chocolate digestive biscuits for a snack. Men can top up to their recommended intake by adding an extra couple of pieces of toast and fruit.

However, for many of us eating that amount of food would lead to weight gain. For others, it wouldn’t even touch the sides.

That’s because we all differ in our resting metabolic rate – the amount of calories our bodies burn over the course of a day to do everything from growing and repairing to breathing and moving. The 2,000 and 2,500 calorie advice is merely a broad generalisation. Many can eat more without seeing the numbers on the scales go up, while others have to eat less to maintain their weight.

“Resting metabolic rate is the largest contributor to total energy output, and therefore the main determinant of how many calories we need each day,” says Dr James King, a reader in clinical exercise science at Loughborough University.

This rate varies depending on sex, height and weight. “It is directly related to body size, specifically the overall amount of bodily tissues we have which need energy to function,” he explains.

“Bigger people will have more tissue, and this largely explains the difference [in calories burned] between men and women. On average, men tend to have more muscle mass, and less fat than women, and because muscle consumes more energy than fat, this also contributes to men’s greater energy requirements.”

Age is also a factor. “Metabolic rate is highest in our very early years, drops from around 20 years of age, remains at that level until around 65 years, and then starts to decline,” Dr King explains.

This means young men can comfortably consume around 3,500 calories per day, despite being officially advised to eat 1,000 calories fewer than this, says Tom Sanders, an emeritus professor of nutrition and dietetics at King’s College London. The UK recommendation is effectively “a one size fits all” approach, he adds.

Beyond our resting metabolic rate, we can influence how many calories we burn through exercise. For example, just half an hour of fast walking can blitz 175 calories, while running can use up 450 – though the calories we burn through exercise will also vary between people. But being physically active increases the number of calories a person needs to consume to stay the same weight, meaning that exercise can also help with weight loss.

While the calorie calculator takes all of these factors into account, it’s important to note that the result is only a rough guide. More advanced options such as calorimeters – which measures the carbon dioxide a person produces and the oxygen they consume to precisely log calories burned – are needed to generate a more precise figure.

If you want to lose weight, experts say that knowing the number of calories you typically burn each day is vital, as you would then need to cut that by 500 per day to lose around 1lb a week. “There is no doubt that restriction of calorie intake results in weight loss,” Prof Sanders says.

To do this, downsize your crockery, cut back on carbohydrates by serving up smaller portions of rice and pasta, avoid regularly eating biscuits, chocolate and crisps, but don’t worry about the calories in fruit and vegetables, he recommends.

However, experts also warn that calories are just one metric to judge food by. Lower calorie options aren’t necessarily healthier and tracking intake too closely can lead to an unhealthy relationship with food.

For those who want to maintain a healthy weight but don’t want to count calories, there are easier ways to tell whether you’re eating the right amount.

Using a tape measure to keep track of your waistline can flag any changes in weight or, even more simply, keep an eye on how well your clothes fit. If your waistband feels tighter than usual, it may be an idea to cut back on unhealthy snacks or slimdown the size of your meals.

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