Páginas: 16 (3817 palabras) Publicado: 23 de febrero de 2012
Carbohydrate provides 4 calories per gram.
Protein provides 4 calories per gram.
Fat provides 9 calories per gram.
As an example of how these numbers are used, imagine a food containing 10 grams of protein, 10 grams of fat, and 10 grams of carbohydrates. That would total 170 calories:
(10g protein x 4) + (10g fat x 9) + (10g carbs x 4)

=40cal from protein + 90cal from fat + 40cal from carbs = 170cal total
In this imaginary food 40 calories come from protein, 90 calories come from fat, and 40 calories come from carbohydrates.

Dietary Reference Intakes published by the USDA:
45% - 65% of calories should come from carbohydrate (take 50%)
10% - 35% of calories should come from protein (take 30%)20% - 35% of calories should come from fat (take 20%)

Estimated Daily Energy Requirements
Age | Sedentary1
Level | Low Active2
Level | Active3
Level |
19-30 y | 2,500 cal | 2,700 cal | 3,000 cal |

Since 1 kg bodyweight equals 7,000 calories, you need to reduce your caloric intake by 1,000 calories per day to lose about 1 kg bodyweight per week.

Food NutrientsMan needs a wide range of nutrients to perform various functions in the body and to lead a healthy life. These nutrients are chemical substances which are present in the food we eat daily. The foods containing these nutrients which we consume daily are classified as cereals, legumes (pulses), nuts and oilseeds, vegetables, fruits, milk and milk products and flesh foods (fish, meat and poultry)Since man derives all the nutrients he needs through the foods he eats, his food must be well balanced to provide all the nutrients in proper proportions.
There are six major classes of nutrients: carbohydrates, fats, minerals, protein, vitamins, and water.

Metabolism is the term used for all chemical reactions in the body. The chemical reactions of metabolism take the food weeat and transform it into fuels and building blocks for the body. These chemical reactions are necessary for providing energy for activities such as movement and thinking, and for organ function such as digestion. These reactions are also critical for breaking down old tissue and building new tissue.
The foods that we consume are chemically complex. They must be broken down by the body intosimpler chemical forms called nutrients. Nutrients are taken in through the intestinal walls and transported by the blood to the cells. The processes involved are called digestion, absorption, and metabolism.
Digestion begins the process through a series of physical and chemical changes by breaking down the food in preparation for absorption from the intestinal tract into the bloodstream. Digestionactually begins when chewing breaks large pieces of food into smaller pieces.
The next step in this process is absorption.
Absorption takes place primarily in the small intestine, where its surface area is comparable to a quarter of a football field. That's pretty amazing, isn't it?
Nutrients are taken up by the intestines and passed into the bloodstream to facilitate cell metabolism. Withinthree to four hours after a meal has been eaten, the body must find a way to absorb millions of nutrient molecules including amino acids (proteins), monosaccharides, monoglycerides, glycerol (carbohydrates), fatty acids and glycerol (fats), vitamins, and minerals.
A whole lot of stuff goes on here, with several hundred cells covered with microscopic hairs in constant motion, trapping nutrientmolecules and digesting and absorbing them into the cells.
By the time we get to metabolism, the handling of food within the body has reached its final stage. The process of metabolism involves all the chemical changes that nutrients undergo from the time they are absorbed until they become part of the body or are excreted from the body. Metabolism is the conversion of the digested nutrients...
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