A calorie is a calorie is a calorie, at least from a thermodynamic point of view. It is defined as the amount of energy required to raise the temperature of one kilogram of water by 1 degree Celsius (2.2 pounds per 1.8 degrees Fahrenheit).
But when it comes to your body’s health and energy balance, not all calories are created equal.
For example, some studies have reported this the regimes that are rich in protein, low in carbohydrates or a combination of both do give greater weight loss than diets with other levels of fat, protein and carbohydrate.
If every calorie in food were the same, you wouldn’t expect to see differences in weight loss among people who ate the same number of calories as those distributed in different types of food.
Dieticians like me Be aware that there are many factors that influence what a calorie means to your body. Here’s what we understand so far about calories and nutrition.
Energy actually available to your body
In the late 1800s, chemist WO Atwater and his colleagues devised a system to determine the amount of energy – that is, the number of calories – in various foods. Basically, he burned food samples and recorded how much energy they gave off as heat.
However, not all of the energy in foods that can be burned in the lab is actually available to your body. What scientists call metabolizable energy is the difference between the total energy of the food consumed and the energy that comes out of your body, undigested, in faeces and urine. For each of the three macronutrients – protein, carbohydrate, and fat – Atwood devised a percentage of the calories they contain that would actually be metabolizable.
According to the Atwater System, it is estimated that one gram of each macronutrient provides a certain number of calories. The US Department of Agriculture still uses these calculations today to official calorie count for each food.
How much energy you use
What You Eat May Affect What Scientists Call Your Body energy costs. This is the amount of energy it takes to keep you alive – the energy you use to breathe, digest, circulate your blood, etc. – as well as what you exercise to move your body. You may have heard this called metabolism.
The quality of the diet can affect the body’s energy expenditure, also known as thermal effect of food. For example, in one study, people consuming the same number of calories per day but following a low-carbohydrate diet or a low-fat diet had differences in total energy expenditure about 300 calories per day. Those who followed a very low-carb diet used the most energy, while those who followed a low-fat diet consumed the least.
In another study, high fat diets led to a decrease in total energy expenditure than high carbohydrate diets. Other researchers have reported that although switching from carbohydrates to fats did not affect energy expenditure, people who increased their protein intake to 30-35% of their diet used more energy.
In general, high carbohydrate diets, fat or both produce a 4% to 8% increase in energy expenditure, while meals high in protein causes an increase of 11% to 14% above resting metabolic rate. Proteins have a higher thermal effect because they are more difficult for the body to break down. While these variations are not huge, they could contribute to the obesity epidemic by encouraging subtle average weight gain.
Quality of calories you eat
Dietitians pay attention to a glycemic index of foods and glycemic load – that is, how quickly and to what extent it will raise your blood sugar. An increase in blood sugar triggers the release of insulin, which in turn influences energy metabolism and the storage of excess energy as fat.
Foods like white rice, cakes, cookies, and crisps all have a high glycemic index / load. Green vegetables, raw peppers, mushrooms, and legumes all have a low glycemic index / load. There is some evidence that foods lower on glycemic index / load Maybe better for keeping blood sugar regulated – whatever calories they contain.
The reward centers in the brain light up when people eat high glycemic index / high load foods, highlighting the pleasant and addictive effect foods like candy or white breads.
The fiber content of foods is another thing to consider. Your body cannot digest fiber – found in plant foods like fruits, vegetables, whole grains, and beans – for energy. Thus, foods high in fiber tend to have less metabolizable energy and can help you feel fuller with fewer calories.
Empty calories – those from foods with minimal or no nutritional value – are another factor to consider. Things like white sugar, sodas, and many ultra-processed snacks don’t provide much, if any, of protein, vitamin, or mineral benefits with their calories. The opposite would be nutrient rich foods high in nutrients or fiber, while being relatively low in calories. Examples are spinach, apples and beans.
And don’t think empty calories are neutral. Nutritionists consider them harmful calories because they can have a negative effect on health. Foods that contribute the most to weight gain are chips, potatoes, sugary drinks and meats, processed and unprocessed. On the other hand, the foods that are inversely associated with weight gain are vegetables, whole grains, fruits, nuts and yogurt.
More for your health than calories and weight
It is indisputable that for weight loss the difference between the number of calories consumed and the number of calories exerted by exercise is the most important factor. But don’t be fooled. While weight plays a role in health and longevity, weight loss alone is not synonymous with health.
Yes, some high protein diets seem to promote weight loss at least in the short term. But epidemiologists know that in areas where people live the longest – almost 100 years on average – they eating a diet that is mostly plant-based, with very little or no animal protein and little or no fat in the form of mono- and polyunsaturated fat.
I often hear friends or clients say things like “these are the carbs that make me fat” or “I need to be on a low carb diet”. But these complaints drive dietitians like me, well, nuts. Carbohydrates include foods like Coke and candy canes, but also apples and spinach. Cutting back on simple carbohydrates like soft drinks, baked goods made from refined flour, pasta and sweets will definitely have a positive impact on health. But cutting out carbohydrates like vegetables and fruits will have the opposite effect.
Plant-based food rich in vegetable proteins and carbohydrates mainly from vegetables, fruits, nuts and legumes is the healthiest diet researchers know for longevity and the prevention of chronic diseases like heart disease, cancer, hypertension and many other conditions.
Modern western food suffers from a increase in the amount of calories consumed with a competitor decreased calorie quality consumes. And researchers now know that calories from different foods have different effects on satiety, insulin response, the process of converting carbohydrates into body fat and metabolic energy expenditure.
When it comes to your health, count more on the quality of the calories you consume than on the number of calories.
[Get the best of The Conversation, every weekend. Sign up for our weekly newsletter.]