Experts say that the ideal diet consists of 40% of carbohydrates, 30% of fats and 30% of proteins; personally, I disagree and believe that time and scientific progress will prove me right:
- The ideal, in my opinion, is 40% of proteins, 30% of good carbohydrates and 30% of good fats;
- Even better is for a qualified functional nutritionist to calculate the most suitable diet for your specific needs.
However, if, regardless of the composition of their diet, many people accumulate so much body fat, where does it come from? The answer is simple: mainly from the excesses committed; be it fats, carbohydrates or even proteins.
Fats: When they enter the body, they can form part of its structure (cell membranes, hormones, etc.) or what is left over (excess!) can be incorporated by the adipocytes (or liver) and deposited, thus forming an energy reserve (fat stores much more energy in less space...); an important detail: fat can never be transformed into proteins or carbohydrates, as some people mistakenly think, but excess carbohydrates are transformed into fat!
Carbohydrates: Also called “sugars” (even if they aren't necessarily sweet, like pasta and bread), when they enter the body they are used to produce energy or stored in the form of glycogen (a relatively small stock, made by the liver and muscles) or whatever is left over (excess!) is incorporated by the adipocytes (or liver), transformed into fat and deposited, thus making up an energy reserve (after all: fat stores much more energy in less space!).) is incorporated by the adipocytes (or liver), transformed into fat and deposited, thus making up an energy reserve (after all, remember: fat stores much more energy in less space)... That's right: as glucose is a carbohydrate, the main source of energy for the brain and heart, if glucose is lacking the liver can turn proteins into carbohydrates; in other words, in “emergency” situations (very common in those who eat poorly or exercise beyond their capabilities), your body can break down your proteins (whether they are in muscles, bones or wherever) to turn them into “sugars”.
Proteins: When they enter the body, they are used predominantly for structural purposes, i.e. to form its various components, but whatever is left over (excess!) can be converted by the liver into glucose (via gluconeogenesis); and we know what happens to excess glucose, don't we? (if you have any questions, read again above).
In other words, everything becomes fat if it enters the body in excess... Question answered?
Everything in this sentence excludes vitamins, minerals and water, which are never transformed into fat by our bodies; the most that can happen is that changes in their quantities alter appetite, metabolism, biotransformations (proteins into glucose, glucose into fat, etc.), etc.
Cheers,
Dr. Ícaro Alves Alcântara
Português do Brasil 
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