Get ready because a can of worms is well and truly going to be opened here.

Calories are perhaps what much of the population will most associate with a healthy diet, healthier foods or weight loss.

Unfortunately this is not the best way to think about good nutrition.

The long-standing prevalent thought related to weight loss/gain is that it is a matter of energy balance, i.e. calories-in vs. calories-out.


The concept of energy balance and body composition can be simplified as the following:

If our calorie intake matches how many calories we burn we stay the same weight.

calorie in

If we consume more calories than we use up (positive energy balance) we will put on weight.

calories out

And if we consume less calories than we use up than use, we will lose weight.


People like this model because it is logical and easy to follow. However, if this model were correct then the problem of overweight/obesity would be solved by the common advice to “eat less/exercise more”.

It’s not.

And that’s because it’s not all about calories.

Here are 3 reasons why.


It is crucial to realise that calories-in and calories-out are not independent of one another. In other words, one affects the other.

Let’s take a practical example. Take someone who starts eating a severely calorie-restricted diet. What happens? Over time they become more tired and find themselves to be unable to sustain the same amount of physical activity. Summary: Calories-out are reduced because of a reduction in calories-in.

The energy balance concept also begins to fall apart when we distinguish between what is actually being ‘lost’ when we refer to weight loss. If we reduce calories-in to lose weight, the amounts of each body tissue that are lost will have a knock on effect on calories-out. If we lose mainly muscle tissue we will see a much greater drop in calories-out as muscle is much more active metabolically than fat tissue.

The complexity of the human body and the biochemistry that underpins human nutrition means that we cannot simply know what effects calories will have on our bodies by using a simple maths equation.

You may have perhaps heard that 3,500 calories is equivalent to a pound of fat. So, as the theory goes, in order to lose a pound of body fat you need to create a deficit of 3,500 calories. If we take this to be over a week we end up with the commonly quoted “fact” of needing to create a deficit of 500 calories each day.

Similarly, if we create a surplus of 3,500 calorie we will put on a pound of body fat.

But our bodies just don’t work that way.

If this were really true then imagine just how exact and precise our energy balance would have to be in order just to stay the same weight. Let’s put some figures to this as an example:

Consider an average man, who does almost no exercise, will have a daily requirement in excess of 2,000 calories. If we accept the energy balance concept and the idea that 3,500 calories equals a pound of fat, then we would expect the following scenarios to be true:
Eating just 50 calories (say, 2 carrots) above maintenance each day would result in a weight gain of 5 pounds in a year!
Changing nothing else but starting to do some ironing for half an hour each day would burn enough calories to drop 8 pounds over the course of the year.

This simply doesn’t happen.

It wouldn’t make sense for our bodies to be so sensitive to such small changes.

Think about it. Many people stay the same weight (within a pound or so) for many years on end, despite not needing to track the composition of every piece of food they eat or by living in a metabolic research lab working out exactly how much energy they are expending.

Why? Because human metabolism doesn’t follow a simple maths equation.


In recent times a wave of opposition to the calories-in/calories-out concept has emerged. One of the advantages most often touted of eating low-carb and/or paleo, is that body composition and health improves without the need to count calories.

Designing your diet by choosing foods solely on the basis of calories completely misses the point. Sure, you may be eating a suitable amount of calories but are you getting enough vitamins and minerals? Are the foods in your diet leading to rapid blood sugar spikes and crashes? What effect is your diet having on your hormone production?

Calories are not all created equal. Foods of the same calorie composition can have very different effects on our bodies.

The impressive Dr. Robert Lustig is one of those who often raises this point. He gives four simple examples demonstrating why “a calorie is not a calorie”:

  1. Fiber.
    You eat 160 calories in almonds, but you absorb only 130. The fiber in the almonds delays absorption of calories into the bloodstream, delivering those calories to the bacteria in your intestine, which chew them up. Because a calorie is not a calorie.
  2. Protein.
    When it comes to food, you have to put energy in to get energy out. You have to put twice as much energy in to metabolize protein as you do carbohydrate; this is called the thermic effect of food. So protein wastes more energy in its processing. Plus protein reduces hunger better than carbohydrate. Because a calorie is not a calorie.
  3. Fat.
    All fats release nine calories per gram when burned. But omega-3 fats are heart-healthy and will save your life, while trans fats clog your arteries, leading to a heart attack. Because a calorie is not a calorie.
  4. Sugar.
    This is the “big kahuna” of the “big lie.” Sugar is not one chemical. It’s two. Glucose is the energy of life. Every cell in every organism on the planet can burn glucose for energy. Glucose is mildly sweet, but not very interesting (think molasses). Fructose is an entirely different animal. Fructose is very sweet, the molecule we seek. Both burn at four calories per gram. If fructose were just like glucose, then sugar or high-fructose corn syrup (HFCS) would be just like starch. But fructose is not glucose. Because a calorie is not a calorie.

Source: Huffington Post


Body composition is largely affected by hormones like leptin, insulin, lipoprotein lipase and many, many more.

While calorie intake does affect the action of these hormones, the type of food we eat plays a larger role.

This is such an extensive topic that we won’t get into a detailed discussion right now. I will however point out a couple of things that show how hormones can affect our body composition regardless of energy balance.

We know that high-carbohydrate diets increase insulin levels. Elevated insulin causes lipoprotein lipase to pull fat into our fat cells in those who are inactive and/or put on weight easily.

Micronutrient deficiencies have been found to affect the action of leptin and insulin. Therefore, eating a diet of the “correct” amount of calories but with little in the way of nutrient-density could lead to hormonal problems which could in turn affect body fat storage and release.

In his AMAZING recent Timed talk, Peter Attia discussed the hypothesis that perhaps obesity is a RESULT of insulin resistance, rather than a cause as is often thought. If this is indeed prove to be the case, imagine what that would do to the current advice to simply “lose weight” given to overweight diabetics/pre-diabetics.


  • Realise that your body metabolises different foods very differently.
  • Choosing the foods you eat based on whether they are high-calorie or low-calorie is NOT the best nutrition strategy for improving your health.
  • Focus on the nutrient-density of the foods and whether or not they contain any toxins (gluten, fructose, hydrogenated oil, MSG, etc.)

So calories don’t matter right?

Well, not exactly.

Calories DO matter. Just not in the way we are led to believe.

Click here for our prospectus

See you then!

By Danny Lennon