Want to lose excess fat? There’s one method scientifically proven to work: the calorie deficit. In simple terms, that means eating a little less food than your body needs to fuel itself each day.
Do that, and your body starts dipping into its energy reserves – its stored fat – to make up the shortfall.
It sounds straightforward, but anyone who’s tried to lose weight this way knows the story.
You dutifully keep track of the calories in every meal – right down to the last grain of rice – to ensure your daily total remains below your regular tally, and yet the needle on the bathroom scales refuses to budge.
It’s frustrating and disheartening. But there’s good news: you’re not to blame.
Recent scientific findings suggest it’s almost impossible to count calories with any degree of accuracy. Now, that alone explains why trying to lose weight by calorie counting is so hard, and should come as some reassurance to anyone struggling to do it.
But it doesn’t stop there. It seems the very idea of what a ‘calorie’ actually is might need a rethink, especially for anyone who’s serious about losing fat.
Mission impossible
It’s hard to keep track of the calories you consume. But the worst part is, you can make every possible effort to get the count right and you’re still likely to get it wrong – even if you’re a weight-loss specialist.
“Trying to reliably measure how many calories I’m eating – let alone how many calories I’m burning – is a near-impossible task,” says Dr Adam Collins, associate professor of nutrition at the University of Surrey.
It’s not bad maths that trips most of us up, though. Anyone who’s ever tried to judge what counts as a ‘small’ bowl of cereal or a ‘drizzle’ of olive oil knows that estimating portion sizes – and matching them to the numbers on the packet – is anything but straightforward.
Generally, unless you diligently log every ingredient before you eat (and let your meals go cold in the process), humans just aren’t very good at recalling exactly what was on their plate, let alone the handful of snacks they ate without thinking.
Given all that, it’s no surprise that studies suggest the average person underestimates their daily intake by around 30 per cent (roughly 600–750 calories), or about 10 digestive biscuits.
Burning questions
But let’s say, for argument’s sake, you went all in – bringing kitchen scales, a calculator and the clinical composure of a lab technician to every meal (along with the focus needed to ignore the pitying glances of friends and family as you solemnly weigh a crouton).
It still wouldn’t be worth it.
Why? Because there’s a fundamental inaccuracy baked into the very idea of what constitutes a calorie.
The numbers we use to calculate the calories in our food date back to the 19th century, when American chemist Wilbur Olin Atwater first used calories to measure the energy in food.
Atwater’s team burnt hundreds of foods and measured how much heat they produced – a bit like you might burn a lump of coal to see how effective a fuel source it is.
The more heat it produces, the more energy it contains. (Sidenote: with more than 7,000 kcals per kg, coal is a very rich source of energy, but the many impurities it contains means it’s definitely not one you should ever eat).
After all their experiments, Atwater’s team came up with a set of numbers to convert grams of food into calories of energy: four calories per gram of carbohydrate or protein, and nine calories per gram of fat.
We’re still using the exact same numbers today. Prof Giles Yeo, an endocrinologist at the University of Cambridge, says that’s a problem.
“Atwater did a pretty damn good job, but these numbers are more than 120 years old,” he says. “And even at the beginning, the numbers were rounded.”
But it’s not just that the rounded numbers are vague; they’re also based on foods we don’t eat much of anymore. Atwater experimented on foods such as veal, mutton, fowl, condensed milk and turnip – not a doughnut or cereal bar in sight.
“Atwater only tested the foods they were eating at the time,” says Yeo. “These foods were a mile away from what we eat today.
He never did the sums on a modern diet, and I think we might get some different numbers [if we did the same experiments today].”
Atwater’s calculations also didn’t account for the thermic effect of food – the fact that your body burns calories by breaking down certain nutrients. For example, your body uses around 30 calories for every 100 calories of protein it absorbs, something your typical food label doesn’t reflect.
A moving target
In short, the very idea of a food having a simple calorific value is problematic. And that’s before we even consider the effect your individual biology can have.
Two people can extract very different amounts of energy from the same foods, because their gut microbiomes don’t break that food down the same way.
This not only affects how many calories you absorb, but also how many you pass out the other end.
For instance, a 2023 study tested the outcomes of giving people a high-fibre diet, designed to feed their gut microbes.
With growing microbial communities in their guts, the scientists found that the participants in the study lost a little bit of weight – without eating less or feeling hungry – because they were absorbing fewer calories from their food.
“Not all calories are the same,” says Prof Rosa Krajmalnik-Brown, a co-author of the study and director of the Biodesign Center for Health Through Microbiomes at Arizona State University in the US.
“Some are used by you, while others feed your intestinal microbes. A calorie doesn’t indicate where its energy will end up, or whether that energy will feed your gut microbes.”
That means, depending on what you eat and how many microbes are thriving in your gut, different amounts of the calories in your food may actually be converted into energy.
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What's the alternative?
If all this is starting to make you think that calorie counting might be doomed, you’d be right. At least, that’s according to Yeo. “My point isn’t that we need better calorie counting,” he says. “It’s that I don’t think we should calorie-count at all.”
So, if counting calories is off the menu, what’s the alternative? Well, there are four other ways to approach weight loss that not only have the potential to improve your diet, they’re also a whole lot simpler than trying to count calories…
Master your macros
If the idea of carefully keeping track of your food still appeals, you could count macros instead of calories. Macros – short for macronutrients – are the large components of food: carbohydrate, protein, fat and fibre.
You can count all the macronutrients if you like (all four are important for a healthy diet, particularly if you’re doing a lot of exercise), but the experts recommend focusing on protein and fibre.
Not only because sources of those macronutrients typically contain sufficient amounts of carbohydrates and fat anyway, but because fibre and protein have a special trick up their sleeves: they help you feel fuller for longer.
This means that by increasing your fibre and protein consumption, you’ll probably end up eating less overall, because you won’t feel hungry so often.
“Fibre tends to add bulk to your food,” says Dr Emily Leeming, a dietitian at King’s College London. “That can stretch the muscles of your gut and your stomach, which triggers sensory nerves, called stretch receptors, to send messages to your brain telling it that you’re full and satiated.”
A lack of fibre may be one reason people overeat. Several studies show that leaner people tend to eat more of it. Yet, despite the recommended amount being 30g of fibre a day, adults in the UK average around 20g, and in the US, just 14g.
In other words, your mum was right: you should be eating more fruit and vegetables. Both are good sources of fibre, but you can also find it in nuts, seeds, legumes and wholegrains.
Meanwhile, protein is similarly satiating, so foods rich in protein (think lean meats, fish, eggs, dairy products, beans, lentils, legumes and soy products) will help you feel full even while you’re cutting back.
By contrast, there’s no fixed daily recommendation for protein – your needs shift with age, activity levels and overall physiology.
Most guidelines suggest a minimum of 0.75g of protein per kilogram of bodyweight per day, but Leeming says it’s better to aim higher: around 1.2–1.6g/kg for the average healthy adult.
In practical terms, that’s roughly 78–104g of protein a day for a 65kg adult – or about 3–4oz for someone who weighs 150lb. Do that and, much like fibre, you’ll feel fuller for longer. Conversely, straightforward calorie cutting tends to make people feel more hungry, not less.
Balance your plate
You don’t need to study a nutrition table to lose weight – it’s all about paying attention to what’s actually on your plate. Especially as, according to Collins, good-old-fashioned food groups serve as a rough approximation for macros.
He recommends ensuring that you aim to have a portion of each food group on your plate at every meal: protein (such as meat, fish, eggs, cheese, tofu or legumes), starchy carbohydrates (including pasta, rice, bread, potatoes or wholegrains) and vegetables or fruit.
Getting all these food groups into your meals can help you make sure you don’t over-fuel while getting a good balance of nutrients, Collins explains.
And if you want to be more specific about it, Leeming recommends filling half your plate with fruit and veg, and a quarter with wholegrains, to make sure you’re getting all the fibre you need.
Taking this approach means you can easily adjust your plate to align with your other health goals.
“If, for example, I’m doing a lot of exercise, I might increase the protein and carbohydrate portions,” Collins says. “On a day without exercise, I might focus on the fruit and vegetables.”
A review from 2024 concluded that eating a good range of all the food groups could make you feel full and energised, aid your body build and maintain muscle, and help with weight management.
And it could do this more sustainably than diets that cut out most of a food group, such as a low-carbohydrate or low-fat diet, according to the author.
So, keeping your plate balanced should help you to eat a good range of nutrients and feel full on only three meals per day, meaning that you’re less likely to overeat in terms of calories – without having to count a thing.
Minimise UPFs
Ultra-processed foods (UPFs), as you’ve probably heard by now, don’t come straight from a farm. They’re made in factories using ingredients you wouldn’t find in your kitchen, and methods that would be difficult to replicate at home.
They dominate supermarket shelves and Western diets, making up nearly 60 per cent of all the calories consumed in the UK and US.
“UPFs, by their nature, are high in calories, fat, sugar and salt,” says Collins. “They’re highly palatable, readily available and easy to overconsume. So, if you’re relying on those types of foods all the time, you’re likely to run the risk of oversupply.”
A striking National Institutes of Health study from 2019 put this to the test.
Twenty adults of similar age and body mass index lived in a clinic for four weeks, rotating between two diets: one comprising UPFs; the other minimally processed foods. The meals were matched for calories and nutrients, but participants could eat freely.
The result: people on the ultra-processed diet consumed about 500 extra calories a day.
The problem wasn’t just the extra calories, though. It’s that those extra calories were coming from UPFs – foods that contain less fibre and protein. This makes UPFs easier to digest, so you burn less energy as you break them down.
What that means is, as well as consuming more calories by eating UPFs, you’re also using less of them to digest the surplus food that you’re consuming.
Minimally processed foods, with their higher fibre and protein content, are much harder to digest in comparison. And research bears this out.
In a 2023 study, participants who ate a whole-food, high-fibre diet lost an average of 116 calories more per day in their poop compared to those following a standard Western diet that included more UPFs.
That’s why Yeo recommends sticking to minimally processed foods, wherever possible, to help you reduce your calories and eat more healthily without even thinking about it.
“You’ll notice there aren’t calorie counts on fresh food,” he says. “But if you’re eating only whole foods, the likelihood of you having to worry about calories is probably lower.”
Choose your food wisely
Cutting down on the UPFs in your diet helps you reduce the amount of food you eat, while also improving its quality. But that’s not to say you have to swear off UPFs altogether. Yeo acknowledges that’s not a realistic goal for most people.
“In an ideal world, we should be eating as many whole foods as possible – actual meat and actual vegetables,” he says. “But that would mean fixing the entire food environment.”
Besides which, he adds, like the calorie, the very concept of UPFs is problematic too. “It includes too many foods that are technically ultra-processed, but actually are fine for you.”
For instance, a study carried out in 2024 found that, while eating more UPFs overall was associated with a higher risk of type 2 diabetes, there were some exceptions to the rule.
Certain foods – such as sliced bread, plant-based ‘meat’ and wholegrain cereals – were associated with a lower risk of type 2 diabetes. So, not all UPFs are equally unhealthy.
And when you’re trying to choose a specific product – frozen lasagne, for example – Yeo recommends comparing the fibre and protein content of different brands to roughly guess their quality.
“Is it better to eat actual tofu or steak or fish? Of course it is,” says Yeo. “But an ultra-processed protein bar that’s higher in protein is likely to be better than another ultra-processed bar that has less protein.”
By doing this, you can give yourself the best chance of choosing healthier foods and losing weight, even without cutting ultra-processed products completely out of your diet – or needing to count a single calorie.
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