If you listened to the diet gurus, you’d think that ‘calorie’ was a swear word. High-calorie is bad, right? Low-calorie is good? Well, actually, it’s not that simple.
You see your body needs energy to grow, move, think, stay healthy and generally function. It gets that energy from everything you eat and drink. The more energy you use – for example, if you live an active lifestyle – the more energy your body needs.
Calories are units that nutritionists use to measure how much energy a food or drink gives you.
Thing is, not all calories are created equal. Let’s look at why…
Why all the fuss about calories?
Why do so many people obsess about them? Mostly it’s because two dudes in the 1920s came up with the idea of counting them as a way to mathematise dieting (and make a motza in the process). But that’s a story for another day.
Calories are just one way to look at how your body functions. If you take in more calories than your body uses as energy, then it stores it as fat.
As humans, we needed that store of energy when we lived in a world where food might be plentiful today, but hard to find the next. But that’s not the case anymore. We live in a world where food is always available, and we rarely use up the energy we’ve stored.
The amount of calories in any given food depends on two things:
- What macronutrients are in it: macronutrients are ‘the big three’ of nutrition: carbohydrates (carbs), protein and fats. A food’s macronutrient content, plus its fibre and water, determine its calories.
Carbs and proteins both have around four calories per gram. Fat has around nine. And neither fibre nor water has any. So you can see how the balance of carbs, fats, proteins, fibre and water affects the calorie count.
- How much you eat: obviously, the more of a food you eat, the more calories it will provide. That’s why nutritionists normally specify a portion size when they talk about the nutrients in a food.
When you take that into consideration, you start to see why not all calories are equal.
Why are calories from different sources different?
One thing you’ll often hear health experts talk about is the ‘quality’ of calories in food. That simply means what other nutrients the food contains, OTHER than the calories. Nutrients are compounds your body needs to do its job, and they include:
- vitamins and minerals
- essential amino acids and fatty acids
Let’s look at the number versus the quality of calories by comparing 100 calories each of:
- Jelly snakes: about two or three lollies will give you 100 calories, which come from 96 per cent simple carbs (sugar) and 4 per cent protein. They have ZERO other nutrients.
- Zucchini noodles: 5 CUPS(!) of raw zucchini will also give you 100 calories, which come from about 73 per cent carbs, 18 per cent protein, and 9 per cent fat. That zucchini will also give you 25 per cent of your daily fibre intake, plus a large handful of B-group vitamins, Vitamin A and C, and various minerals. Oh, and it’s almost 95 per cent water, which has no calories at all.
So while both portions provide 100 calories, it’s clear which one has quality calories and which just has empty energy.
It’s also clear why foods such as fruits, vegetables and legumes are usually lower in calories than foods with high levels of fat or protein.
But is every food calorie the same to your body?
OK, so we’ve talked above about why different foods have different calorie counts, and why some are described as ‘quality calories’ while others aren’t.
But what happens once you’ve actually eaten a calorie? Are all calories the same once they hit your stomach?
Interestingly, no. Studies show that calories from different foods are absorbed differently. Your body uses more energy to break down and use protein than it uses for either carbs or fat. Researchers estimate that:
- for every 100 calories of protein you eat, you’ll get 75 calories of energy
- for every 100 calories of fat, you’ll get 98 calories
- for every 100 calories of carbs, you’ll get 93 calories
In other words, you’ll get more calories from fat and carbs than you will from protein.
How our bodies use (and respond to) macronutrients
Our bodies are elaborate structures that contain trillions of cells, each of which works around the clock. Those cells also have all kinds of specialist roles, just one of which is converting the food we eat into energy.
Here’s how our bodies use and respond to protein, fat and carbs. We’re going to get a bit science-y. Strap yourselves in.
Your body breaks down protein into amino acids, which it uses to build and repair cells, to create hormones, and – if you’re not getting enough carbs – for energy. And because proteins are often complicated, it can take your digestive system a while to break them down.
That means foods with a lot of protein will often help to keep you feeling fuller for longer. So not only do you get fewer calories from the food, but you can also go longer before you get hungry again.
Experts are wildly divided when it comes to how much protein is enough. Recommendations for what proportion of your daily calories should come from it range anywhere from 10 per cent to 35 per cent
To up your protein intake the natural way, include high-protein foods like lean meat, seafood, eggs, dairy foods, legumes (eg. peas, beans and chickpeas) and nuts.
Fats get a really bad rep, but they’re an important part of our diet that help to keep us healthy. Fat enables the body to absorb essential vitamins, is vital for healthy cell walls, supports our immunity, and helps to slow down digestion too – plus it’s a rich source of energy. So… tick, tick, tick, tick.
BUT… not all fats are alike. Monounsaturated fats like the ones in avocados, nuts and olives, and polyunsaturated fats like the ones in fish oil or some vegetable oils,are good for us. Saturated fats like the ones in butter or meat… probably aren’t.
And most scientists agree that trans-fats (vegetable fats that start off liquid, then get chemically altered to stay solid) are the worst of the worst.
So you absolutely need some good fats in your diet, but be careful about which ones you include.
Wait – does fat lead to obesity?
Remember how we said earlier that your body stores the extra calories you don’t immediately use up as fat so they’re there for you to draw on later? Well, that means that too much of ANY food can lead to obesity.
And remember that fat is energy-rich at 9 calories per gram. So, that means it’s easy to eat more calories than you realise when you eat fat-rich foods. But if you watch your portion size, then no, fat won’t automatically lead to obesity.
Does sugar lead to obesity?
Again, eating too much of ANYTHING can lead to obesity. But much like fat-rich foods, it’s super easy to take in more calories than you realise when you’re eating high-sugar foods. And, unlike with fats, unless those foods are whole fruits and veggies, they don’t normally have much in the way of quality calories.
So again: watch your portion size, and try to stick to whole, natural foods and drinks made with zero calorie natural sweeteners.
Your body breaks ALL carbs down into glucose – the sugar molecule that your cells prefer to use for energy. (Fun fact: cells only use fats and proteins for energy if they have no other choice – glucose is definitely their preferred way to go.)
So food experts divide carbs into two groups – simple and complex – according to how easy they are to break down.
Simple carbs (AKA ‘sugars’) are easy for your body to break down. That means they’re great for a short-term energy hit, but not so great for sustained energy. And unless you use them up immediately – eg. in an intense workout – they create a blood sugar rollercoaster of a spike followed by a crash, which is just one of the reasons why sugar is bad for you.
You’ll find simple carbs in refined starches like white rice, white flour and white pasta (notice a pattern there?) They’re also in many fruits and the occasional veggie. The difference is that in fruits and veggies, you’re also getting fibre, water and nutrients, all of which get stripped out when you eat processed simple carbs.
Complex carbs are harder for your body to break down. That means you get longer-term, more sustained energy from them. And because you find them in foods that contain a fair amount of fibre, those foods tend to be lower in calories. They also tend to keep you feeling full for longer.
Good foods for complex carbs include brown rice, wholegrain breads and cereals, and some starchy veggies. And not only are these foods rich in fibre, but they also tend to have a bunch of important vitamins, minerals and other nutrients.
Variety is the spice of life (and of health too!)
We all need calories for energy, but we get far more than just calories from our food. We also need a range of the other nutrients we talked about earlier in the article – vitamins, minerals, essential amino and fatty acids, etc.
That makes it vital to get your calories from a wide variety of different foods. According to the Australian Government’s Health Direct site, a healthy, balanced diet includes foods from each of the five food groups every day. This means:
- vegetables and legumes
- grains and cereals
- lean meat, poultry, fish, eggs, tofu, nuts and seeds
- milk, cheese, yoghurt or alternatives
Now you know, not all calories are created equal
While technically, a calorie is a calorie is a calorie, science has shown us that not all calories are created equal. For example:
- depending on whether they’re in carbs, protein or fat, there are different amounts in the same volume of food
- depending on whether calories are in carbs, protein or fat, your body absorbs and uses them differently
- depending on how processed or refined a food is, calories can be high-quality and nutritious or empty and a waste of energy
And, calorie for calorie, it’s always better to eat foods that are chock-full of nutrients than those that are nutritionally ‘empty’.