Myth: A Calorie Is A Calorie

“A calorie is a calorie” is a term we’ve all heard from fitness experts and health enthusiasts, however, the notion is not as simple as it seems.

Different foods undergo different biochemical pathways to be metabolised. Obesity researchers have pointed out that calories from different foods have different effects on satiation, insulin response and energy expenditure. Furthermore, different foods have varied responses on hormones and brain centres that control hunger and eating behaviour.

But how does this impact calorie storage?

Let’s begin with thermodynamics. The thermic effect of food is the amount of energy it takes for your body to absorb, digest and metabolise the foods you consume based on the varied metabolic pathways they move through.

Carbohydrates and fats move through much more efficiently than protein, meaning the amount of energy consumed to metabolise protein is higher, i.e. fewer calories stored. Calories from whole foods, such as vegetables, fruits and beans, require more energy to metabolise, compared to processed foods.

For example, the thermic effect of protein is roughly 25%, while the thermic effect of fat is about 2%. If you consume 100 calories from protein, this would mean 75 calories will be stored, while 100 calories from fat would total 98 calories once metabolised.

Secondly, some foods are more palatable than others, leading us to eat more before reaching satiety. Our neural circuity contains opioid receptors which increase dopamine after the consumption of certain foods. This perpetuates a reward system when eating foods combining fats, salt and sugar - a combination not typically found in nature. Food manufacturers have discovered the ‘sweet spot’ in this combination to keep consumers wanting more.

Glucose and fructose are the two main simple sugars we consume. These two sugars contain the same amount of calories gram for gram, however, they are metabolised very differently.

Glucose leads to increased feelings of fullness, compared to fructose. This is because glucose reduces the levels of ghrelin, the hunger hormone. The higher the levels of ghrelin, the hungrier you will feel. Increased consumption of fructose, compared to glucose, also leads to a greater risk of insulin resistance, fat gain in the abdominal region and higher levels of LDL cholesterol.

This isn’t to demonise fructose. The effect lies in the source of fructose. For example, fruits contain fructose that is bound by nutrients, fibre and water - negating its negative effects, compared to sweets containing added fructose and little to no nutrients and fibre.

Judging your energy intake based solely on the calories you consume, rather than the quality of foods you eat is much too simplistic. Understanding that different foods result in varied caloric stores and energy expenditure is vital when controlling body weight.

If you’re needing help with weight management, or simply want to know what foods you should be eating to feel your best, make an appointment. Together we can explore your concerns to formulate a treatment plan specific to you.