viernes, 19 de noviembre de 2010

Energy and foods

Energy has traditionally been expressed as calories or kilocalories.. The energy value of a particular food is calculated from a knowledge of macronutrient composition It indicates its value to the body as a fuel. The energy value for each macronutrient are:

Fat9 kcal/g
Alcohol7 kcal/g
Protein4 kcal/g
Carbohydrate4 kcal/g

Fat is the most energy-dense macronutrient, followed by alcohol, protein and carbohydrate. For example, a glass of full-cream milk has about twice the kilocalories as a glass of soft drink or of skimmed milk Dietary fibre or roughage is not usually ascribed an energy value for humans. Vitamins and elements have no energy value.

Energy requirement can be thought of as the amount needed to maintain the basic processes of life at rest, that is, basal metabolism, plus the amount needed for physical activity under a variety of circumstances. Body weight is an important factor in determining how much energy we need, since more energy will be needed to sustain and move a greater body mass. The total amount of food needed each day will vary with age, sex, body size, activity levels, and whether or not you are pregnant or breastfeeding.

There are a Harris Benedict ecuation for calculating basal metabolic rate (BMR):

BMR Women = 655 + (9,6 x W) + (1,8 x H) - (4,7 x A)
BMR Men = 66 + (13,7 x W) + (5 x H) - (6,8 x A)

Where W = weigh in kg; H = height in cm ; and A = age in years

You can also get it directly in same websites.(This website uses English units, so you have to remenber: 1 foot = 0,304 meters and lbs/2.2 = kilograms)
Other posibility is to go to a Spanish website. Maybe in this way it will be easier.
One of the easiest ways To calculate your total daily energy expenditure (calories) is with other Harris Benedict Equation that uses your BMR and then applies an activity factor to determine it. The only factor omitted by the Harris Benedict Equation is lean body mass. Remember, leaner bodies need more calories than less leaner ones.

To determine your total daily calorie needs, multiply your BMR by the appropriate activity factor, as follows:
• If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2
• If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375
• If you are moderatetely active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55
• If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725
• If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9

Total Calorie Needs Example
If you are sedentary, multiply your BMR (1745) by 1.2 = 2094. This is the total number of calories you need in order to maintain your current weight.
Once you know the number of calories needed to maintain your weight, you can easily calculate the number of calories you need to eat in order to gain or lose weight:
Calorie Needs to gain weight. If you want to gain body weight, you need to consume more calories than you burn. One pound (0,45 kg) of body weight is roughly equivalent to 3,500 calories, so eating an extra 500 calories per day will cause you to gain one pound a week.
For optimum health, if you increase your calories to gain weight then (health permitting) gradually increase your level of physical exercise in order to maintain or increase your lean body mass. The benefits of exercise on physical and mental health are well documented and shouldn't be ignored.
Calorie Needs to lose weight. There are approximately 3,500 calories in a pound of stored body fat. So, if you create a 3500-calorie deficit through diet, exercise or a combination of both, you will lose one pound of body weight.

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