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Energy balance is a state of balance between the energy supplied with food and the costs of various life processes of the body. That is, if you spend more than you consume, then the weight should decrease. But is it really so?
The principle of energy balance, in fact, repeats the physical law of conservation of energy or the first law of thermodynamics: energy cannot be created or destroyed, it can only be transformed from one form to another.
Changes in the body’s energy reserves are equal to the difference between energy intake from food and consumption. In theory, everything is simple. Eat (that is, get energy from food) exactly as much as you spend. Spend as much as you eat and this will ensure that you maintain your original weight. Eat less than you spend, and you will lose weight; eat more than you spend, and the weight will increase.
Does diet affect weight if energy balance is observed?
To find out, we conducted several experiments. So, in a 1992 study (Energy intake required to maintain body weight is not affected by wide variation in diet composition), volunteers were placed in a metabolic chamber for 30 days. For each subject, the caloric intake norm was determined, covering his individual energy expenditure, which was supposed to ensure the invariance of body weight. Similar products were used to feed the subjects, however, the composition of the diet differed in the percentage of macronutrients. One group received a high-fat diet, the other – a high-carbohydrate diet, with an exact correspondence of energy intake to individual energy expenditure. After a month of such controlled nutrition, the weight of each participant remained unchanged, regardless of the composition of the diet.
In 2004, the results of a retrospective analysis of completed studies on the effect on body weight of diets with different macronutrient compositions were published. The conclusion was unequivocal: provided that the energy balance is maintained, the composition of the diet does not matter.
One of the most radical experiments to confirm the paramount importance of energy balance was conducted on himself in 2010 by Mark Haub (Professor at Kansas State University): he ate exclusively confectionery and sweets for 60 days, while maintaining a calorie deficit. At the end of the experiment, his weight decreased by 12 kg, which once again proved that the energy balance works.
So, if the energy consumption rate to maintain a person’s weight is 2000 kcal, and he eats fast food products (fries, hamburgers, sweet soda), while receiving 1500 kcal, weight loss will inevitably occur (what will happen to this person’s health is another question ). If he eats only healthy food, for example, steamed fish, fresh vegetables, getting 3000 kcal, the weight will inevitably increase.
Why doesn’t this always happen in reality?
“I don’t eat anything and I’m getting fat”, “I keep a diet, but my weight stays the same” and at the same time “I eat without denying myself anything, and I’m not getting better.” Doesn’t the first law of thermodynamics work in these cases? Of course, this is not so, the law is unchanged, but there are nuances. Let’s see what else needs to be considered.
The thermal effect of food
All processes occurring in the body require energy, the processes of digestion of food are also energy-consuming. Part of the energy that comes with food is spent on its processing and assimilation. It has been experimentally established that the digestion of fats takes up to 3% of the calories received, carbohydrates – up to 10%, proteins – up to 20-30%. For the average value of such energy expenditure with a balanced and varied diet, 10% is taken. However, it should be remembered that the digestion of food that has undergone a minimum of processing, such as fresh fibrous vegetables, is more energy-intensive than the digestion of such refined foods as sausages, buns, chocolate.
Assimilation rate
The more refined, that is, the more stages of industrial processing the food has gone through, the faster it is digested and absorbed, and the less the feeling of satiety remains. The opposite is also true: minimally processed food takes longer to digest, which means that the desire to eat does not arise longer. It is logical that a person who is accustomed to refined food without additional control will eat more during the day.
Saturation
Meals of the same calorie content affect the feeling of satiety in different ways. Fats and fiber slow down the emptying of the stomach, and the feeling of fullness lasts longer than when eating starchy foods or simple carbohydrates. Fibrous meat satiates for a longer period than tender fish or eggs.
That is, some products create a long-lasting feeling of satiety with fewer calories. Other foods do not saturate even with a large number of calories. This does not violate the law of income-expenditure of calories, but only affects eating behavior.
Some foods make you want to lie on the couch and sleep, make you lethargic and sleepy. Others, on the contrary, are cheerful and energetic.
Taste
The tastier the food, the more you can eat. But there is a big difference between simply delicious healthy food and “drug” delicious food that hyperstimulates the tongue’s taste buds and the brain’s dopamine (pleasure) receptors. Most often, a person perceives a very tasty mixture of sweet or salty with fat, melting or crunchy texture, it is these combinations that lead to uncontrolled overeating.
