Does it matter what I eat? A calorie is a calorie, right? Well… not exactly. You’ve probably heard that “a calorie is a calorie,” and while that’s true for matters relating purely to energy balance and weight loss and gain, a calorie is not a calorie when we’re talking body composition and health. We don’t want just to gain and lose weight, right? Our goal is more specific: we want to gain more muscle than fat, and we want to lose fat, not muscle. And with those goals, we have to watch more than just calories. Simply counting calories is not enough. We have to watch our macro-nutrient intake, too. In this article we’ll try to explain the main reasons why a calorie is not a calorie. You will never reach your fitness and bodybuilding goals (e.g. improve your body composition) if you follow only calorie counting principle.

Reasons why you may think that all calories are the same

A calorie is a unit of energy, not food, so in that regard calories are all the same.

The idea that simply counting calories and following the “calories in, calories out” philosophy is the answer to health and successful weight management is highly misunderstood. The energy balance equation will tell you that in order to achieve weight gain you have to take in more calories than your body uses. And vice versa, for weight loss it’s necessary to reduce energy intake below energy use. Finally, as long as your caloric input equals caloric output, you will neither gain or lose weight.

For this simple concept it doesn’t matter where those calories come from or how you burn them. This pure mathematical concept is based solely on counting calories ingested and consumed. Intuition probably tells you that things can never be that simple. And it’s right. The human body is far more complicated than a simple math equation, so understanding why a calorie is not a calorie is vitally important to our health.


same amount of calories from different food sources

The image above clearly shows the following:

  • Different foods have different effects on your body, even if they contain the same number of calories. This is the main reason why all calories are not equal.
  • Both plates (plate A and plate B) provide a total of 660 calories.
  • Can you lose weight by eating only food items from the plate A? Yes, you can, at least for a while. As long as you consume fewer calories than you expend (burn) each day you will lose weight, even with plate A on your table. However, there’s a catch!
  • Food items from plate A are extremely unhealthy. In addition to their calorie content, these treats are loaded with sugar and saturated fats. They do not provide your body with quality proteins (essential amino-acids), complex (slow-released) carbohydrates and healthy fats. Refined sugars provide calories but they lack vitamins, minerals, antioxidants and dietary fiber. These food items will provide a quick burst of energy. However, the rapidly falling blood sugar levels that follow the consumption of high-GI foods may increase cravings and appetite, potentially increasing food intake and contributing to obesity. Last but not least, you have only 134 grams of food on your plate.
  • On the contrary, plate B provides the same amount of calories while providing your body with healthy carbs (especially fibers), high-quality sources of protein and fat. Finally, you consume 742 g of healthy foods (rich in vitamins and minerals) for the same number of calories.

Unless you’re getting nutritionally dense foods, your body will remain hungry. The bottom line? Count nutrients, not only calories. The nutrient quality of calorie is more important that just quantity. Although you will lose extra pounds for a while, your body composition will remain miserable.

Reasons why a calorie is not a calorie

Not all food is created equal when it comes to how the calorie is treated once it enters your body.

Here are the main reason why a calorie is not a calorie. Here’s why all calories are not equal!

#1 Different foods go through different metabolic pathways

It costs your body different amounts of energy to digest different foods. Different sources of calories have different effects on your body, even if they contain the same number of calories. Once ingested, proteins, carbohydrate and fats are digested, absorbed and metabolised by the body. The energy required for these processes differs between the various macronutrients. Some of the calories you consume are used up digesting the food and turning it into fuel available to the body. This is called the thermic effect of food, or thermogenesis.

For example, the body uses more calories to digest and metabolise protein than it does carbohydrate or fat. When you consume protein, approximately 25-30 per cent is “wasted” or lost as heat. In contrast, 6-8 per cent of the calories consumed in the form of carbohydrate and 2-3 per cent of the calories in fat are used up in digesting it. In other words, carbohydrate and fat are relatively easy for the body to turn into energy. Protein needs to be broken down into amino acids, which is a far more complex process. So if you eat 100 calories of protein, only about 70-75 will be absorbed – the rest is lost as heat.

#2 Some sources of calories are more filling than others

You also need to consider the effects the different macronutrients have on satiety (how full up they make you feel). Protein has the highest satiating effect, with refined carbohydrate having the lowest satiating effect. So 100 calories of steak will make you feet more satiated than 100 calories of crisps. Right?

We’re sure that you can confirm from your own experience that some foods leave you feeling full faster so your appetite is gone in a flash. Other foods with the same number of calories are less filling, keeping your appetite going and going and going. Therefore, you want to seek out the first type of foods.

#3 Different foods provide different amounts of energy for a given weight

The amount of energy you get from a food depends on where those calories come from (i.e. protein, carbohydrate, fat, or alcohol). Therefore, the energy value of a food depends on the amount of carbohydrate, protein, fat, fiber and alcohol it contains. Because these nutrients have different chemical structures, they provide different amounts of energy. The energy values for carbohydrate and protein are approximately 4 kCal per gram. However, 1 g of fat contains more than twice the number of kcalories as 1 g of carbohydrate or protein (9 kCal/g). The fuel factor for alcohol (7 kCal/g) falls midway between fat and that of carbohydrate and protein.

#4 Certain type of calories cause unwanted hormonal responses

Some types of calories can alter levels of hormones in your brain and cause you to eat more. For example, sugar promotes overconsumption because it acts on the areas in the brain involved with reward and cravings. Protein, fat and low-GI (non-sweetened) carbohydrate, on the other hand, are less likely to make you want to eat more after consuming them.

#5 Food preparation affects the way the body uses the calories in that food

How you prepare food effects the way the body uses the calories in that food. That is, cooking, grinding and fermenting food. For example, mice lose weight when they only eat raw sweet potato, but gain weight eating cooked sweet potato. Additionally, mice gain a little weight when eating raw meat, but gain more weight with eating cooked meat. Now if that isn’t a case for eating more raw food!

#6 100 calories in a high-fiber will be more satiating than 100 calories in a low fiber food

Fiber is not absorbed into the body but leaves us feeling full and satisfied with far fewer calories than their low fiber counterparts. A person who increases their daily fiber intake without trying to eat less will wind up eating less anyway, due to reduced appetite.

all calories are not created equal

Closing thoughts: Why calorie is not a calorie?

In summary, when looking purely from a measurement perspective, all calories are equal, but in terms of weight management and health, they are not. Different calorie sources can have vastly different effects on hunger, hormones, energy expenditure and the brain regions that control food intake. The quality of the sources can affect your health dramatically. That’s why you need to focus on the quality of the calories you’re eating and not simply count calories. A good rule of thumb is to avoid foods with empty calories. By consciously choosing more nutrient-dense foods, you’ll get the beneficial nutrients your body needs without consuming too many calories. That way, the calories we’re eating are worth it.

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