It’s one of the most debated questions in nutrition: Are all calories equal?
The short answer is No, they are not.
While a calorie represents a fixed unit of energy in a lab, your body does not treat every calorie the same way. This is where the idea of Caloric Availability comes in.
Caloric availability is one of those ideas that can make everything about weight loss finally click. It explains why you can eat the same number of calories from two different meals and feel completely different afterwards. It also explains why some people can create more of a calorie deficit without eating fewer calories. Once you understand it, you realise your body is a digestive system, a set of hormones, a metabolism, and a brain that respond to food very differently depending on what you put in. I am not saying that calories in-calories out doesn’t count – it does – but you can make your food work harder for you when on a diet.
If you have ever wondered why eating whole foods feels so different from eating ultra processed foods, or why high protein diets work so well even when calories stay the same, caloric availability is what you have been sensing all along. As an online weight loss coach, many of my clients notice this difference firsthand when they first change their eating habits for the better (but this doesn’t mean being perfect all of the time though).
What does caloric availability mean?
Caloric availability is simply the number of calories your body actually absorbs and can use from the food you eat. It is not the number on the packet. It is not the number you track. It is what your body ends up with once it has digested, broken down, absorbed, and processed the food.
Two people can eat the same meal and absorb different amounts. Two meals with the same calories on paper can give you completely different levels of energy. And two diets with the same total calories can lead to very different results depending on what those calories are made of.
This is why weight loss is not only about eating less, it is also about choosing foods that give you lower caloric availability or higher digestive effort without feeling like you are dieting.
Why two foods with the same calories behave differently
The easiest way to explain this is with the coaching example I always use with my clients: imagine you ate 2000 calories of Haribo (if only!) versus 2,000 calories of chicken breast. On paper they are the same. In your body they are nothing alike.
With Haribo your body absorbs almost every calorie because processed sugar requires very little digestion. It hits your bloodstream quickly, it does not fill you up for long, and your body does not burn much energy breaking it down. You might absorb something like 1900 to 1950 calories out of the 2,000.
With chicken breast your body has to work much harder. Protein takes time to digest. Your digestive system uses energy during the process. You stay fuller for longer. You absorb slightly fewer calories because the structure of the protein and the way your body handles it is so different from a handful of sweets. From 2000 calories of chicken breast, your body might end up with roughly 1500 to 1600 once you account for the thermic effect of food.
These are approximate numbers – and I am obviously not expecting you to actually eat this – and they vary from person to person, but the principle is solid. Even though they are both 2000 calories, the amount your body gets from each is completely different, and the effect on hunger and energy is different too.
It is worth saying, if in both examples you are in still a calorie deficit you will still lose weight as, again, calories in-calories does matter and there is no getting around that. But with with the chicken example, you would be in a larger deficit and are also likely to feel more full.
The thermic effect of food
The thermic effect of food is the energy your body uses to digest and process the food you eat. Protein has the highest thermic effect, which is one of the reasons high protein diets work so well for fat loss. Your body uses a noticeable amount of energy simply digesting it. Carbohydrates vary, and fats require almost no energy to break down.
This means you can create an extar calorie deficit without eating fewer calories just by adjusting the balance of foods. Adding more protein and more whole foods can naturally increase the number of calories your body burns through digestion.
It is not magic. It is just biology working in your favour.
Digestion, fibre, and how many calories you absorb
Another part of caloric availability is absorption. Not everything you eat is absorbed perfectly. Foods that contain more fibre tend to give you fewer absorbed calories because fibre moves through the digestive system without being fully broken down. This is why whole fruit digests differently from fruit juice and why whole grains have a different effect than white bread.
Some foods are famous for this. Nuts are a good example. Research shows that the calories on the label are not the calories the average person absorbs because the fat in whole nuts is physically harder to access. If you turn those nuts into nut butter you absorb far more because the structure has already been broken down.
Your digestion, gut health, chewing habits, cooking methods, and even how quickly you eat all change how many calories end up being absorbed.
How to use caloric availability to create an extra deficit without eating less calories
You do not need to track caloric availability. You just need to understand how to make it work for you.
Some of the simplest ways to create a natural calorie deficit include:
- Eat more protein with each meal
- Choose foods closer to their natural structure
- Include fibre rich foods regularly
- Swap ultra processed foods for more whole food versions
- Slow down your meals and chew more
- Lift weights to improve how your body uses energy
This approach keeps meals satisfying and helps you avoid the constant hunger that makes diets fail.
Everyday examples that show caloric availability in action
Once you see the principle, you notice it everywhere:
- A whole apple fills you up more and gives you fewer absorbed calories than a glass of apple juice.
- A bowl of oats leaves you fuller for longer than a bowl of Coco Pops even if the calories match.
- Chicken breast behaves differently from pizza even when the calorie total is similar.
- Lentils digest differently from white rice.
- Whole almonds give you fewer absorbed calories than almond butter.
None of this means you can never eat processed food. It simply means whole foods help your metabolism naturally work harder.
How caloric availability changes as we age
Caloric availability is not fixed. It often changes with age, especially for women around menopause. Hormonal shifts, changes in muscle mass, stress levels, sleep quality, and digestive changes can all affect how efficiently your body uses or stores energy.
This is one reason people say their metabolism has slowed down even though they feel they are eating the same way. It is usually a mix of reduced muscle, slightly lower activity, and changes in digestion rather than a broken metabolism.
Understanding caloric availability helps you make realistic changes rather than feeling like your body is working against you.
Should you track it?
No. It is far too complex to calculate. But when you understand it, you stop relying on the numbers alone and start choosing meals that help your body work efficiently. Tracking can still be useful, but the food choices within your calories matter just as much as the total.
Who benefits from understanding caloric availability?
Almost everyone who has ever been confused by weight loss. It helps if:
- Your weight feels stuck
- You feel hungrier than you expect
- You are over 40 and noticing changes in energy
- You are a gym-goer, runner or cyclist trying to fuel well
- You struggle with IBS or digestive sensitivities
- You want to feel more in control of your eating without dieting harder
It brings a sense of logic and relief to the whole process.
FAQs
Are all calories equal?
All calories contain the same amount of energy on paper, but your body does not treat them all equally. A calorie from chicken breast is not the same as a calorie from Haribo, for example, because the digestion process is completely different. Some foods take more work to break down. Some foods pass through your system with fewer calories absorbed. Some affect your hunger hormones more effectively. So while the number is the same, the effect on your body is not. This is why calories still matter, but the quality of those calories shapes how your body responds to them.
How many calories do we actually absorb?
There is no exact number because it varies from person to person and meal to meal. Your gut health, the texture of the food, cooking method, chewing, fibre content, and whether the food is processed all make a difference. Some meals are almost fully absorbed. Others lose a noticeable percentage during digestion. For example, whole nuts can lose a good chunk of calories in the digestive process, while sweets are almost fully absorbed. This is why focusing on whole foods naturally reduces absorbed calories without dieting harder.
Does fibre reduce calorie absorption?
Yes, fibre can reduce calorie absorption because your body cannot fully break it down. When you eat high fibre foods the calories are packaged inside a structure that your digestive system cannot always access completely. Some of the calories pass through unused. This is why whole fruit, vegetables, lentils, beans, and whole grains help with weight loss. They are not just lower in calories, they also reduce the number of calories your body absorbs from the entire meal.
Do nuts give fewer calories than the label says?
Yes, whole nuts often give you fewer calories than the label suggests because the fat is locked inside the nut’s structure. Your body has to work hard to break that down and it does not always succeed fully. When you turn nuts into nut butter you absorb far more because the mechanical work has already been done. This does not mean nuts are free though, but it does mean they behave differently depending on how processed they are.
Can you speed up your metabolism naturally?
You can influence it, but you cannot change it dramatically overnight. The main things that help are increasing your protein intake, eating more whole foods, lifting weights to build or maintain muscle, staying active throughout the day, and getting enough sleep. These habits increase the energy your body uses while digesting food and during rest, which can make sustainable weight management easier without extreme dieting.
Want help working out what foods to eat?
If you want to make this simple, practical, and tailored to your lifestyle, I can help. My online weight loss coaching takes all the guesswork out of eating for weight loss, energy, and long term health. I work with busy people who want structure, accountability, and a plan that actually fits their real life rather than forcing them into a strict diet.
If you want personalised support, weekly check ins, and guidance that helps you lose weight without feeling restricted, book a free consultation.
