Zitat:
The old school of nutrition, which often includes most nutritionists, is a calorie is a calorie when it comes to gaining or losing weight. That weight loss or weight gain is strictly a matter of "calories in, calories out." Translated, if you "burn" more calories than you take in, you will lose weight regardless of the calorie source and if you eat more calories than you burn off each day, you will gain weight, regardless of the calorie source.
This long held and accepted view of nutrition is based on the fact that protein and carbs contain approx 4 calories per gram and fat approximately 9 calories per gram and the source of those calories matters not. They base this on the many studies that finds if one reduces calories by X number each day, weight loss is the result and so it goes if you add X number of calories above what you use each day for gaining weight.
However, the "calories in calories out" mantra fails to take into account modern research that finds that fats, carbs, and proteins have very different effects on the metabolism via countless pathways, such as their effects on hormones (e.g., insulin, leptin, glucagon, etc), effects on hunger and appetite, thermic effects (heat production), effects on uncoupling proteins (UCPs), and 1000 other effects that could be mentioned.
Even worse, this school of thought fails to take into account the fact that even within a macro nutrient, they too can have different effects on metabolism. This school of thought ignores the ever mounting volume of studies that have found diets with different macro nutrient ratios with identical calorie intakes have different effects on body composition, cholesterol levels, oxidative stress, etc.
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The "Calories Don't Matter" School Of Thought
This school of thought will typically tell you that if you eat large amounts of some particular macro nutrient in their magic ratios, calories don't matter. For example, followers of ketogenic style diets that consist of high fat intakes and very low carbohydrate intakes (i.e., Atkins, etc.) often maintain calories don't matter in such a diet.
Others maintain if you eat very high protein intakes with very low fat and carbohydrate intakes, calories don't matter. Like the old school, this school fails to take into account the effects such diets have on various pathways and ignore the simple realities of human physiology, not to mention the laws of thermodynamics!
The reality is, although it's clear different macro nutrients in different amounts and ratios have different effects on weight loss, fat loss, and other metabolic effects, calories do matter. They always have and they always will. The data, and real world experience of millions of dieters, is quite clear on that reality.
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Diets that give the same macro nutrient ratio to all people (e.g., 40/30/30, or 70,30,10, etc.) regardless of total calories, goals, activity levels, etc., will always be less than optimal. Optimal macro nutrient ratios can change with total calories and other variables.
...One man's food, one man's poison...