Macronutrient
A macronutrient is one of the three nutrients the body uses for energy in gram quantities — protein, carbohydrate and fat — together with alcohol, which also supplies calories but serves no nutritional purpose.
Everything with calories in it is some combination of four things. Learning their energy values is most of what you need to read a nutrition label.
The energy values
Protein supplies about 4 kcal per gram. Carbohydrate supplies about 4 kcal per gram. Fat supplies about 9 kcal per gram, more than twice as much, which is why cooking oil is the single most under-counted item in home cooking. Alcohol supplies about 7 kcal per gram.
These are the Atwater factors, and they are averages rather than exact constants. Fibre, for instance, yields less than 4 kcal per gram because it is only partly fermented rather than fully absorbed, and different countries' labelling rules handle that differently.
What they are for
Protein supplies amino acids for building and repairing tissue, and is the macronutrient with a genuine daily requirement in the sense that a shortfall costs you something. Fat is required for hormone production and for absorbing fat-soluble vitamins, and there is a minimum below which people feel unwell. Carbohydrate is the body's preferred fuel for hard training but has no strict dietary requirement, which is why very low-carbohydrate diets are survivable even though most people dislike training on them.
Why the totals matter more than the split
Calories decide the direction of weight change; the split between the three mostly decides how you feel while it happens.
स्रोत
- 1.Dietary Reference Values — European Food Safety Authority
- 2.Food energy: methods of analysis and conversion factors — Food and Agriculture Organization of the United Nations
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