Calorie counting has long been the most popular and widely used diet method. But recent research into how different foods affect the body has revealed that it may not always be helpful.
At a basic level, it’s true that in order to lose weight, you need to burn more calories than you consume. But this simple equation misses out many other key factors; including the nutritional value of food, and the way it affects our metabolism, appetite, cravings, and overall health.
Below, we’ll take a closer look at how and why calories differ – and why choices about the types of foods we eat are just as important as the calories they contain.
What is a calorie?
Calories are the standard unit used to measure energy. Our bodies rely on energy from calories to function properly.
Almost all food and drink items contain energy that’s locked away in chemical bonds. When food and drink are broken down (or metabolised) by the body, this energy is released.
The calories we use to talk about the amount of energy that food and drink contain are actually kilocalories (kcal) – a unit that equals 1,000 calories. This is because it’s much easier to say that one medium banana contains 105kcal than 105,000 calories.
As a general guide, the NHS recommends that the average man and woman should consume 2,500kcal and 2,000kcal a day, respectively. However, this figure can vary significantly, depending on factors such as age, weight, height, and activity levels.
6 shortfalls of calorie counting – why it does matter what food you eat
While all calories contain the same amount of energy, when it comes to how they interact with the body and affect health, not all calories are created equal.
This means that there are several shortfalls to calorie counting, which we’ll cover below.
1. Calorie counting doesn’t account for the nutritional value of food
Foods that contain the same number of calories can have vastly different nutritional content, and, therefore, very different effects on health.
On the one hand, nutrient-dense foods like fruit and vegetables are fantastic sources of various essential vitamins and minerals. As a result, eating a diet rich in nutrient-dense foods is linked with healthy weight maintenance and a reduced risk of health conditions like asthma, heart disease, and type 2 diabetes.
Meanwhile, ultra-processed foods such as pizza, crisps, and doughnuts offer little to no nutritional benefit, tend to be high in saturated fat, salt, and added sugar, and are linked with an increased risk of chronic health conditions and early death.
For example, 150g of blueberries contains similar calories to one chocolate digestive biscuit. But while blueberries are a rich source of fibre, vitamins A and C, and potassium, and contain little to no salt or fat, chocolate digestives offer no nutritional benefit, and are high in added sugar.
2. The body has to work harder to break down certain foods
Another area that calorie counting doesn’t account for is how different foods affect our metabolism.
Metabolism is a term used to describe all of the chemical reactions that happen in the body to keep you alive and functioning – including the process of using energy to break down nutrients in food. Experts refer to this as the thermic effect of food (TEF).
Research shows that protein causes the largest rise in TEF because the body has to work harder (and, therefore, use more energy) to digest and absorb it. In fact, studies show that protein temporarily increases metabolism by 15-30%, compared to 5-10% for carbohydrates and 0-3% for fats.
For this reason, there’s evidence that increasing your protein intake to 25-30% of daily calories may help you burn an extra 80-100 calories per day.
3. Food has varying effects on appetite and feelings of fullness
Research shows that foods can have vastly different effects on appetite and how satisfied we feel after we eat. This means that what we eat can significantly impact our eating habits and ability to lose weight.
As well as speeding up our metabolism, protein can be particularly helpful for regulating appetite and keeping food cravings at bay. Of the three main macronutrients (carbohydrates, fat, and protein), we know from research that protein is by far the most filling. As such, there’s evidence that high-protein diets may naturally reduce appetite and cause people to eat fewer calories without trying.
In this study, when people increased their protein intake from 15% to 30% of daily calories, they ate an average of 441 fewer calories a day and lost 4.9kg over 12 weeks. Another study of overweight men found that, when they increased their protein intake to 25% of daily calories, their food cravings were reduced by 60% and their desire to snack at night by 50%.
The same goes for whole foods which, unlike ultra-processed foods, haven’t been stripped of key nutrients like fibre, and take longer for the body to break down. Studies show that people who eat mostly whole foods naturally eat less, compared to those who eat lots of ultra-processed foods.
If you think about it, it can be quite easy to eat 400 calories or more of biscuits, but you’d likely have to force yourself to eat 400 calories of carrots or eggs. Plus, not only do ultra-processed foods often leave us unsatisfied, but studies show they that actually increase appetite and lead to food cravings too.
Unfortunately, manufacturers are well aware of this and so purposefully add sugar, salt, and other addictive ingredients to encourage us to buy their products over and over again. Take this research from the BBC, which revealed that when people ate ultra-processed food, they consumed an extra 500 calories a day compared to when they ate unprocessed meals.
4. Food significantly impacts how energised we feel
While all food provides us with energy, the type of energy can vary significantly. Some foods provide long-lasting, steady sources of energy, and others cause short-lived energy spikes.
Much of this comes down to the impact that food has on blood sugar levels, as high blood sugar and blood sugar spikes can cause tiredness and fatigue.
The glycemic index (GI) is a ranking system used to measure the impact of carbohydrate-containing foods on blood sugar levels. It can be a useful indicator of how energised a food is likely to make us feel. Generally speaking, the higher the GI rating of a food, the more likely it is to spike blood sugar and cause energy crashes.
Much of this rating system comes down to whether a carbohydrate is simple or complex. All carbohydrates are made from chains of sugar molecules that the body breaks down into glucose for energy. However, complex carbohydrate chains are longer and take the body more time to digest, providing longer-lasting energy. Meanwhile, simple carbohydrates rapidly release sugar into the bloodstream and cause sudden energy spikes, followed by sudden dips.
White bread, cookies, and cakes are examples of high-GI foods, while whole grains, chickpeas, and lentils are considered low-GI.
As well as causing tiredness and fatigue, high blood sugar is also linked with an increased risk of conditions like diabetes and heart disease. So, research shows that low GI diets may be beneficial for overall health too.
For more information, check out our articles; 12 energy-boosting foods and drinks and The low glycemic (GI) diet – what is it and are there benefits?
5. The foods we eat affect our mental health
We all know that diet has a huge influence on our physical health. But studies continually show its role in mental health too – which is another area that calorie counting alone doesn’t account for.
The gut-brain axis (which is the connection between the gut and central nervous system and how they influence each other) helps to explain the connection between diet and mental health.
The brain and gut are in constant communication, and so our diet choices can significantly impact how we think and feel. In fact, research suggests that the gut microbiome can directly influence brain signals and activate areas of the brain responsible for regulating emotions. The gut-brain connection is so intricate that many experts refer to the gut as the ‘second brain’.
This study found that diets rich in fruit, vegetables, whole grains, and legumes, and low in processed meats lowered the risk of depression. Meanwhile, other studies have identified links between stress, anxiety, and mental health issues with high intake of saturated fat and added sugar, low fruit and vegetable intake, and overall poor diet quality.
Besides its importance for mental wellbeing, the connection between diet and mental health is worth noting if your goal is weight loss. Research has consistently linked anxiety with overeating, and depression with emotional eating.
6. Calorie counting can foster an unhealthy relationship with food
Last but not least, it’s worth mentioning that, in some cases, calorie counting can foster an unhealthy relationship with food.
In particular, calorie counting may not be suitable for those with a history of disordered eating. Alternative approaches, such as intuitive eating, may be much more beneficial.
As revealed by this study of people diagnosed with an eating disorder, 75% said they used an online tool to track their calories, and 73% felt this contributed to their eating disorders. Various other studies also suggest that weighing food or using calorie trackers may encourage unhealthy eating habits in some people.
Note: If you’re struggling with your relationship with food, it’s important to speak to your GP or seek support from charities such as Beat.
Final thoughts…
Calorie counting has long been one of the most popular and widely used weight loss tools. However, while at a basic level, it’s true that to drop weight you need to consume fewer calories than you burn, when it comes to health, mood, appetite, and sustainable weight loss, not all calories are created equal, and what we eat really does matter.
For further reading, head over to the diet and nutrition section of our website. Here, you’ll find information on everything from important nutrients you could be missing from your diet to quick and easy diet swaps for a healthier lifestyle.
In what ways have you noticed foods affecting you differently? Did anything in our article surprise you? We’d be interested to hear from you in the comments below.
