Not long ago, no dieter would have attempted to drop a few pounds without meticulously recording that day’s “number”: the total calories they’d consumed. Whether calculated on a scrap of paper or logged in an app such as MyFitnessPal, this weight-control calculation was as familiar to many of us as the words “low fat”. 

Recently, though, counting calories has fallen out of fashion. With obesity levels soaring – affecting about one in four people in Britain – weight-loss science has become increasingly complex. Factors such as psychology, genetic predisposition and the impact of ultra-processed food on the hormones that control appetite are all now acknowledged to play a part in our propensity to gain weight. 

Research has also shown that while very low-calorie diets work in the short term, most dieters will later revert to their previous weight. As a result, the most popular weight-loss plans of the past decade have been based on easier-to-maintain intermittent fasting, such as 5:2, which involves eating very little on two days and normally on five; or 16:8, involving abstaining from food for 16 hours and eating within an eight-hour window. 

However, despite all the obesity research that has gone on, the fundamental equation hasn’t changed: to lose weight, we must consume fewer calories. All diets, including intermittent fasting, work on this basis. There’s no quick fix, just a variety of methods to ensure that we’re reducing the number of calories we eat – and if, say, we skip breakfast because we’re fasting, but eat twice as many calories at lunch, the diet isn’t going to work.

It might not be fashionable to talk about calories, but, as the NHS emphasises, understanding them remains crucial when it comes to determining how much we can eat, and maintain a healthy weight. 

“Overall energy balance is really important, by which we mean the energy we put into our bodies versus the energy we expend,” says Dr Laura Brown, senior lecturer in nutrition, food and health sciences at Teesside University. “That means calories are still important. We can eat all the healthiest foods – nuts, seeds, avocados, oils, whole grains – but if our energy intake is too high in terms of calories, we will still gain weight.”

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• Decade by decade: the calories we really need
• Case study: ‘I lost two stone through calorie counting’

Good calories vs bad 

Put simply, calories are units that measure how much energy is contained in a particular food or drink. We “burn” calories through metabolic processes, which break down the carbohydrates into sugars, the fats into glycerol and fatty acids, and the proteins into amino acids. These are transported through the bloodstream to the cells, providing them with the energy required to sustain all the body’s functions, from breathing to moving – with any excess being stored as fat.  

Different nutrients provide different amounts of energy: carbohydrates and protein each provide four calories per gram and fat provides nine calories per gram. 

Not all calories are created equal, however. “Good” calories are nutrient-dense, whereas “bad” are those that are nutritionally “empty”, coming from ingredients such as sugar, refined flours, unhealthy fats and artificial additives. 

“An avocado might have more calories than a chocolate bar, but the avocado will provide you with good fat, fibre, nutrients and vitamins, whereas the chocolate has high sugar and fat, but little to no nutritional value,” says nutritionist Laura Southern, founder of London Food Therapy.

Why food marketed as low calorie isn’t the answer 

When we’re trying to cut calories, it’s tempting to reach for calorie-controlled ready meals and snacks, in which the calculation work has been done for us. While they might help us to lose weight in the short term, they’re bad news for our general health. 

“Food labelled ‘low calorie’ tends to be low in nutrients and high in additives and other ingredients, such as sugar and salt, which have negative long-term effects on our health,” says Claire Cohen, founder of Nat-Nut Nutritional Therapy. Ultra-processed foods, which account for 57 per cent of calories consumed in Britain and are defined as containing manufactured ingredients you wouldn’t find in a home kitchen, have been linked to increases in diseases including cancer and diabetes.

Instead, we should be aiming to fulfil our calorie requirements from the most nourishing foods possible. “Look for foods that provide more than just energy, or calories – think about nutrients, vitamins, minerals, fibres and antioxidants, which give a whole range of health benefits,” says Cohen. “Fruits, vegetables, wholegrains, lean proteins in meat, fish and dairy, then healthy fats, such as avocados, nuts and seeds, oily fish – the kind of good calories that are going to help you feel more satisfied and reduce the likelihood of energy crashes, cravings and overeating.”

The most effective way of counting calories 

Calorie information has been found on food labelling in supermarkets since the 1990s, and since 2021, restaurants with more than 250 staff have been required to print calories on menus. We’ve never had so much access to the calorie content of our food, yet totting it all up remains a daunting prospect for many. As a starting point, Dr Brown suggests using an online calculator to achieve a rough estimate of our energy expenditure. “These can vary in their accuracy, but they generally ask for height, weight, age and activity levels and they can give people an idea of how many calories they need to maintain a healthy weight,” she says.

The NHS has a free 12-week Weight Loss Plan app, which works by calorie-counting, but Cohen recommends the Cronometer app to her clients. “It doesn’t just give you the calories in your food, but also the micro- and macronutrients,” she says. “You can set your daily calorie limit, and also see if you’re hitting the daily recommended amount of protein, carbohydrates, fats and all the vitamins and minerals. So you can see very clearly which ones you’re lacking.”

She warns that, for some, daily tracking over long periods of time can lead to obsessiveness; research has shown that this kind of recording is extremely common among those with eating disorders. “But doing it for a short period gives people a great idea of what’s going on in their normal diet,” she says.  

How many calories do we really need? 

The NHS advises that the average man needs about 2,500 calories per day, while the average woman requires about 2,000. However, this is such a broad generalisation that its use is limited. While most people are aware that our size has a major impact on our calorie requirements – a larger body needs more calories to fuel it – fewer realise that our life stage also has a considerable effect. 

“At different ages, we need different numbers of calories, because our basal metabolic rate, which is the amount of calories the body needs to perform its basic functions, changes over time,” says Cohen.  “As we age, muscle mass gradually declines, and muscle tissue burns more calories at rest than fat tissue does,” she explains. A report released this year by the US National Academies of Sciences, Engineering and Medicine estimated the calorie needs of people in the US and Canada. The research found that calorie requirements drift down each year, by 11 calories per day for men and seven for women, beginning when we’re 19. So, how does what we need differ depending on our life stage?

Decade by decade: the calories we really need

According to research by UCLA statistician Nathan Yau, these are the average daily figures that men and women should aim for if they are in their 30s and moderately active, which is defined as the equivalent of walking 1½-3 miles per day.  

For women who experience childbirth during this decade, their needs will fluctuate: in the last trimester of pregnancy, they need an extra 200 calories per day, while breastfeeding burns about 595 calories per day for the first two months of a baby’s life. In general, says Southern, “This is an age where most people can still get away with indulging themselves to a certain degree.”

Although our calorie needs look similar in our 40s to those in our 30s, this is the decade when most of us notice that shedding the pounds isn’t as straightforward as it once was.

“After 40, our bodies find it easier to gain weight,” says nutritional therapist Claire Cohen. For women, a decrease in the production of oestrogen and progesterone during perimenopause can contribute to weight gain. In fact, changes in hormone levels for both sexes can affect our metabolism from this point onwards. From puberty, growth hormone and insulin-like growth factor 1 slowly decrease by 1-2 per cent each year, and as these levels drop, so does our muscle mass. Another hormone, DHEA, declines by about 2-3 per cent each year after we reach our 30s; lower levels are also linked to lower muscle mass and increased body fat. 

Fifty is the age at which, according to Yau’s research, both men and women begin to require fewer calories. For women, menopause means a slowing metabolism due to declining muscle mass, less exercise and, often, a decline in sleep quality, which can lead them to reach for sugary snacks. This contributes to a weight gain of an average of 1½lb per year.

According to Cohen, who specialises in nutrition during menopause, “At this time we want to make sure we’re increasing our intake of plant protein, such as tofu and beans, which can reduce symptoms and support bone health.” 

Men often find that this is the decade in which they gain weight rapidly, particularly “visceral fat” around their middle, due to declining testosterone levels. “Previously they could eat a lot and burn it off fairly easily, ” says nutritionist Dr Laura Brown. Men aged 45-74 are the category most likely to be overweight or obese – so if they have never paid attention to calorie intake previously, now’s the time to start.

It’s in our 60s and onwards that the age-related drop in the calories we need begins to become most noticeable, often manifesting in a lower appetite. Older people are often less active, but it’s not just our bodies that burn less energy – our brains also naturally shrink in size and require less fuel. “We know from research into the Blue Zones – the places in the world where people live the longest – that longevity and better health in old age are linked to consuming fewer calories,” says Southern. In Okinawa, in Japan, citizens stop eating when they’re 80 per cent full, meaning fewer free radicals are created during the digestive process, leading to a lower risk of cancer and dementia. 

They may require less, but quality is still vital, says Dr Brown. “Older people need to ensure they’re getting plenty of calcium and iron-rich foods and protein to support their health as long as possible.”

‘I lost two stone through calorie counting’

Rogea Rocha, 42, a software engineer who lives in London, used the It’s So Simple app to lose weight

I had always had a relatively good relationship with my body: I was slim and active and ate quite healthily but didn’t really need to worry about my weight. Then I had two babies and the pregnancies – coupled with caring for little ones – had a huge effect. I was overwhelmed by looking after the children, the house and my work and I felt like I didn’t have time to care for myself; I was at the bottom of the pile. It felt like a shallow thing to worry about my health and my weight. 

In November 2020, we moved from the United States to London because of my then-husband’s job. It was incredibly stressful moving countries mid-pandemic, as well as home-schooling my children (now seven and 10) and trying to work as a software engineer. 

My weight went up to just over 11 stone (70kg) which, on my 5’5” frame, felt too big for me. I felt really self-conscious – there are almost no photos of me from that time – and I hated the way clothes felt on me. More than how I looked, my health was suffering. I was tired all the time and lacking in energy to play with the kids, I wasn’t sleeping well, and I was waking in the night with anxious thoughts. 

I hadn’t really dieted before – apart from briefly trying the keto diet with a friend. There, I lost the weight, but quickly put it back on: not eating any carbohydrates was just something I couldn’t maintain. But in April 2022 I found a health coach called Rachael Sacerdoti, who had a really similar story to me, in that she was the mother of three kids and had always put her own health last. She managed to lose 25kg and kept it off, and created a transformation programme, It’s So Simple.

I signed up. It has lots of parts to it, but a fundamental first step is counting calories: whatever else you do, you do need to be in a calorie deficit to lose weight. I’d thought I was eating a relatively healthy diet with lots of vegetables and home-cooked meals. But bad habits had – as for many of us during the pandemic – crept in. My portion sizes had grown. One glass of wine in the evening sometimes became three, and foods that I thought were healthy, like my morning bowl of granola, I soon learned weren’t the best options for me. 

I was advised to go down to about 1,400 calories a day for a start, to help me drop weight. I used MyFitnessPal to track my food, which was so easy to use – there’s a huge database, so you just type it in, or scan a barcode – and you can save your own recipes, so that you don’t have to input them each time. I also sent pictures of each meal to my coaches, who advised on little tweaks I could make to cut calories.

I quickly saw how to make swaps that would help me stick to my calorie target, without leaving me feeling hungry. I saw that red meat – which I love; I’m Brazilian – was often quite a fatty choice (a 4oz steak is around 200 calories and 10g of fat), as are chicken thighs (around 185 calories per thigh and 12g of fat). That’s not to say I couldn’t eat them, but I’d have to balance the calories out in other ways, say for example having a smaller portion of chicken thighs in a salad and then adding in low-fat cottage cheese (half a pot is about 110 calories and 2.7g of fat) or a can of tuna (120 calories and 1g of fat) to bulk up the meal. I also saw how too much “healthy” food can add up; yes, olive oil is good for us, but a tablespoon is around 120 calories, so that can quickly turn a salad into a high-calorie meal if you use too much. It was a really useful lesson.  

Tracking and sending pictures of my meals also showed me that I was tending to overeat at dinner time. I would previously eat relatively well all day, but be really hungry at dinner and have a huge portion. My coaches advised a healthy snack at around 4pm, such as 150g of zero-fat Fage yogurt with berries, which is around 100 calories, but has protein in it that fills you up. It meant then that I could have a lower-calorie dinner later on because I wasn’t starving. 

A hugely important lesson the coaches taught me was that, while calorie tracking is super important, it’s where you get your calories from that really counts. I needed to increase my protein as it’s the most satiating. Carbs aren’t banned as they are on lots of diets – which is great because I really feel like I need them for energy – but you have to be mindful of how many you eat. I tend to go for a chickpea or a lentil pasta if I want that kind of dinner. 

By November 2022, after six months, I reached my goal weight of nine stone (58kg), and I’ve maintained that for almost a year now. When I reached my goal, my coaches increased my calories: I’m now on around 1,900. I still calorie-count and track my meals every day, but during the week I tend to eat a very similar thing every day, so it’s easy. 

The difference losing the weight has made to me has been huge. During my journey, I was going through a divorce, and the support I got from the coaches was immense. Having that to focus on was really important. Now that I’m back where I want to be with my body and weight, I feel so much more confident, which is definitely a bonus now I’m starting to cautiously date again. 

But more importantly, I feel that focusing on healthy change has been really important as a model to my kids. They see me making careful choices and feeding my body things that naturally support it, while still enjoying my food. I’ve got so much more energy to play and be fun that I just feel like a better mother. I’ve learnt that you have to look after yourself first before you can really take care of everyone around you.

Do you count calories to stay slim? Let us know in the comments