Losing weight is a question of getting the balance right. You need to burn more energy or calories than you take in.
On one side of the scales is the energy your body gets from the calories in the food and drink you consume.
On the other side there’s the energy your body uses. Your body burns energy at complete rest, that’s called your basal metabolic rate (BMR). It also uses energy eating and digesting your food. Thirdly it burns up calories when you are physically active.
How many calories you actually need to lose weight and achieve a healthy weight also depends on your weight, age, sex and how much physical activity you do.
There are also variations in different people’s basal metabolic rate that are down to body composition and genetics.
"There are lots of formulas to estimate how many calories you need to lose weight, most were done in the seventies and eighties," says Aisling Pigott, dietitian and spokesperson for the British Dietetic Association.
"As a guideline to maintain your metabolic rate, it’s 2000 calories for women and 2500 for men per day."
She says: "These are averages but the downfall is they don’t account for the individual as everyone has their own needs based on age, sex and muscle to fat ratio."
"I recommend you find out how much you need to eat to maintain your weight and then reduce it by 500 calories a day."
You can do this by trial and error but most people tend to know what they can get away with to avoid putting on weight.
"The formula for most people to lose 1 to 2 pounds a week is to cut their calories by 500 to 1000 a day," says Dr Jane Naufahu, lecturer in human nutrition and performance.
It’s generally agreed that 3500 calories is equal to a pound in terms of weight loss.
So shaving off 500 calories 7 days a week equals a pound.
So in general terms, a woman eating 1,500 calories a day and a man eating 2,000 calories a day, is a good starting point for weight loss.
There are variables. If you have more muscle mass you will burn more calories, as muscle burns more calories than fat. That’s one of the main reasons that men need more calories than women as they naturally have more muscle mass.
You burn fewer calories as you get older as your metabolic rate decreases by around 5% every decade after your 40s. "Young people can get away with having more calories as they have a higher metabolic rate," says Dr Naufahu.
If you are starting off heavier then you have more weight to carry around, so your body is working harder and you’ll be using more calories than a lighter person.
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